Membrane Proteins of Known Structure

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The Monotopic Membrane Proteins have been reorganized. Class 2 Dihydroorotate Dehydrogenases have been added to the list.

This page will soon be converted to a searchable database with many new features. In the course of the conversion, we found the counts of unique proteins and total coördinate files to be inaccurate. The correct values are given below.

If your browser has JavaScript enabled and has a Java plugin installed and enabled, direct links () to a PDB Jmol structure viewer are now available for each database entry.

Last database update: 22 April 2011

New Structures:
A_2A Adenosine Receptor with bound agonist: H. sapiens, 2.71 Å
FocA formate channel at pH 4.0; S. typhimurium, 2.8 Å
CP29 Light-harvesting complex; S. oleracia, 2.80 Å
Metarhodopsin II B. taurus, 3.00 Å
GlpG rhomboid protease; H. influenzae, 2.84 Å
TrkH potassium ion transporter: V. parahaemolyticus, 3.51 Å

Unique proteins* in database = 281.

Number of coördinate files in database = 792.

*Includes proteins of same type from different species. For example, photosynthetic reaction centers from R. viridis and R. sphaeroides are considered unique. Structures of mutagenized versions of proteins already in the database are excluded as unique. Proteins that differ only by substrate bound or by physiological state are also excluded. Structures 'obsoleted' by the PDB are not included. The figure to the right shows the progress of membrane protein structure determination. The figure may be used freely in seminar presentations provided that the URL and lab information on the image are not removed. We thank Ahmed Bakan for bringing some counting errors to our attention, and Tony Crofts, Kenneth Rudd, Ilan Samish, Marcus Stamm, Bill Cramer, and Daniel Inaoka for bringing missing structures to our attention.

This database emphasizes structures determined by diffraction methods, although some NMR structures are included. A comprehensive list of NMR-determined structures is available from Dror Warschawski.

Useful Membrane Protein Structure Resources

Progress of membrane protein structure determination. See also White (2009)

European Membrane Protein Consortium

Martin Caffrey's Membrane Protein Data Bank (Trinity College Dublin)

Bilayer Insertion of Membrane Proteins (Structural Bioinformatics and Computational Biochemistry Unit, Oxford)

Protein Data Bank of Transmembrane Proteins (Institute of Enzymology, Budapest)

Membrane Proteins of Known 3D Structure
(Table description)
Protein	PDB Code	Reference (links are to PubMed)
MONOTOPIC MEMBRANE PROTEINS
Cyclooxygenases
*Ram Prostaglandin H2 synthase-1 (cyclooxygenase-1 or COX-1): Ovis aries, 3.5 Å*	1PRH	Picot et al. (1994)
*Ram Prostaglandin H2 synthase-1 (COX-1): Ovis aries, 3.4 Å* In complex with bromoaspirin.	1PTH	Loll et al. (1995)
*Ram Prostaglandin H2 synthase-1 (COX-1): Ovis aries, 3.1 Å* In complex with flurbiprofen.	1CQE	Garavito et al. (1995)
*Ram Prostaglandin H2 synthase-1 (COX-1): Ovis aries, 2.61 Å* 1EQG is complex with ibuprofen. Complex with flurbiprofen, 2.70 Å: 1EQH Complex with flurbiprofen methyl ester, 2.75 Å: 1HT5 Complex with alclofenac, 2.69 Å: 1HT8	1EQG	Selinsky et al. (2001)
*Ram Prostaglandin H2 synthase-1 (COX-1): Ovis aries, 3.2 Å* In complex with O-actylsalicylhydroxamic acid.	1EBV	Loll et al. (2001)
*Ram Prostaglandin H2 synthase-1 (COX-1): Ovis aries, 2.00 Å* In complex with alpha-methyl-4-biphenyl acetic acid.	1Q4G	Gupta et al. (2004)
*Ram Prostaglandin H2 synthase-1 (COX-1): Ovis aries, 2.00 Å* In complex with flurbiprofen + Mn(III) PPIX cofactor.	2AYL	Gupta et al. (2006)
*Ram Prostaglandin H2 synthase-1 (COX-1): Ovis aries* (expressed in Spodoptera frugiperda), 3.05 Å** 3N8V is the unoccupied structure. R120Q/Native Heterodimer mutant in complex with Flurbiprofen, 2.75 Å: 3N8W COX-1 in complex with Nimesulide, 2.75 Å: 3N8X Aspirin Acetylated COX-1 in Complex with Diclofenac, 2.60 Å: 3N8Y COX-1 in Complex with Flurbiprofen, 2.90 Å: 3N8Z	3N8V	Sidhu et al. (2010)
*Cyclooxygenase-2: Mus Musculus, 3.0Å*	1CX2	Kurumbail et al. (1996)
Squalene-Hopene Cyclases
*Squalene-hopene cyclase: Alicyclobacillus acidocaldarius, 2.0 Å* 2SQC is space group P4₃2₁2. 3SQC, 2.8 Å is P3₂21.	2SQC	Wendt et al. (1999)
Monoamine Oxidases
*Monoamine Oxidase B: Human mitochondrial outer membrane (expressed in Pichia pastoris), 3.0 Å* NOTE: MAOB has a single transmembrane helix that anchors it to the outer membrane (residues 489-515). Nevertheless, we consider it monotopic because the bulk of the 520-residue protein, including the active site, is not located within the membrane core.	1GOS	Binda et al. (2002)
*Monoamine Oxidase B with bound Isatin: Human mitochondrial outer membrane (expressed in Pichia pastoris), 1.70 Å* with bound Tranylcypromine, 2.20 Å: 1OJB with bound N-(2-aminoethyl)-p-chlorobenamide, 2.40 Å: 1OJC with bound Lauryldimethyl-amine N-Oxide, 3.10 Å: 1OJD with bound 1.4-Diphenyl-2-butene, 2.30 Å: 1OJ9	1OJA	Binda et al. (2003)
*Monoamine Oxidase A: Rat mitochondrial outer membrane (expressed in S. cerevisiae), 3.20 Å*	1O5W	Ma et al. (2004)
*Monoamine Oxidase A with bound Clorglycine: Human mitochondrial outer membrane (expressed in Pichia pastoris), 3.00 Å* crystal form B, 3.15 Å: 2BXS Monoamine Oxidase B with bound Deprenyl, 2.20 Å: 2BYB	2BXR	De Colibus et al. (2005)
*Monoamine Oxidase A with bound Harmine: Human mitochondrial outer membrane (expressed in S. cerevisiae), 2.20 Å* G110A mutant with bound Harmine, 2.17 Å: 2Z5Y	2Z5X	Son et al. (2008)
Hydrolases
*Fatty acid amide hydrolase: Rattus norvegicus, 2.8 Å* NOTE: Like MAO, FAAH has a single TM segment. But the active site is external to the membrane, and many other residues on the protein surface contribute to membrane binding. Absence of the TM segment affects neither membrane association or function.	1MT5	Bracey et al. (2002)
Oxidoreductases (Monotopic)
*Sulfide:quinone oxidoreductase in complex with decylubiquinone: Aquifex aeolicus, 2.0 Å* "as-purified" protein, 2.30 Å: 3HYV in complex with aurachin C, 2.9 Å: 3HYX This monotopic membrane protein is thought to be buried about 12 Å in the bilayer interface. Also listed under Oxidoreductases.	3HYW	Marcia et al. (2009)
*Electron Transfer Flavoprotein-ubiquinone oxidoreductase (ETF-QO) with bound UQ: Sus scrofa, 2.5 Å* UQ-free structure, 2.6 Å: 2GMJ. Because this is a mitochondrial respiratory chain protein, it is also listed under Oxidoreductases	2GMH	Zhang et al. (2006)
Peptidoglycan Glycosyltransferases
*Peptidoglycan Glycosyltransferase: Staphylococccus aureus, 2.8 Å* NOTE: The enzyme has a single TM segment, which is absent in the structure. The active site is external to the membrane, but the so-called Jaw Region contributes to membrane binding. 2OLV shows the enzyme complexed with moenomycin. 2OLU is the structure of the apoenzyme.	2OLV	Lovering et al. (2007)
*Peptidoglycan Glycosyltransferase penicillin-binding protein 1a (PBP1a): Aquifex aeolicus* (expressed in E. coli), 2.1 Å** NOTE: The enzyme has a single TM segment, which is absent in the structure. The active site is external to the membrane.	2OQO	Yuan et al. (2007)
*Peptidoglycan Glycosyltransferase penicillin-binding protein 1b (PBP1b): Escherichia coli, 2.16 Å* NOTE: The single TM segment is present in this structure. The active site is external to the membrane. SeMet Protein, 3.09 Å: 3FWL	3FWM	Sung et al. (2009)
Peptidases
*Signal Peptidase (SPase) in complex with a β-lactam inhibitor: Escherichia coli, 1.9 Å* Located in the periplasmic space, the SPase has two transmembrane segments, which are missing in this structure. The Ser-Lys catalytic site is part of a hydrophobic surface that interacts strongly with the membrane.	1B12	Paetzel et al. (1998)
*Signal Peptide Peptidase (SppA), native protein: Eschericia coli, 2.55 Å* SeMet protein, 2.76 Å: 3BEZ. Long thought to be a transmembrane protein, the structure reveals a peripheral homotetramer that likely is buried in the membrane interface. Each monomer has a putative N-terminal transmembrane helix for anchoring to the membrane. This anchor was removed for crystallization. Also listed under Intramembrane Proteases.	3BF0	Kim et al. (2008)
Dehydrogenases
*Glycerol-3-phosphate dehydrogenase (GlpD, native): Escherichia coli, 1.75 Å* SeMet-GlpD, 1.95 Å: 2R4J GlpD-2-PGA, 2.3 Å: 2R45 GlpD-PEP, 2.1 Å: 2R46 GlpD-DHAP, 2.1 Å: 2R4E Also listed under Oxidoreductases.	2QCU	Yeh et al. (2008)
Dihydroorotate Dehydrogenases (DHODH, class 2) Class 1 DHODHs are soluble proteins. Class 2 are membrane associated proteins.
*Dihydroorotate Dehydrogenase: Escherichia coli, 1.70 Å*	1J79	Thoden et al. (2001)
*Dihydroorotate Dehydrogenase: Escherichia coli, 1.90 Å*	1XGE	Lee et al. (2005)
*Dihydroorotate Dehydrogenase in complex with atovaquone: Rattus rattus* (expressed in E. coli), 2.30 Å** DHO in complex with brequinar, 2.40 Å: 1UUO	1UUM	Hansen et al. (2004)
*Dihydroorotate Dehydrogenase, apo form: Homo sapiens* (expressed in E. coli), 3.00 Å** DHODH in complex with brequinar analogue, 2.40 Å: 2PRH DHODH in complex with 'a novel inhibitor', 3.00 Å: 2PRL	2PRM	Walse et al. (2008)
*Dihydroorotate Dehydrogenase with triazolopyrimidine-based inhibitor DSM1: Plasmodium falciparum 3d7* (expressed in E. coli), 2.00 Å** With bound triazolopyrimidine-based inhibitor DSM2, 2.40 Å: 3I68 With bound triazolopyrimidine-based inhibitor DSM74, 2.50 Å: 3I6R	3I65	Deng et al. (2009)
Polymerases
*TagF teichoic acid polymerase: Staphylococcus epidermidis* (expressed in E. coli), 2.70 Å** H444N mutant, 2.81 Å: 3L7J H444N + CDPG, 15' soak, 3.10 Å: 3L7K H444N + CDPG, 30' soak, 2.95 Å: 3L7L H584A mutant, 2.85 Å: 3L7M	3L7I	Lovering et al. (2010)
ADP-Ribosylation Factors
*ADP-ribosylation factor (ARF1), myristoylated: Saccharomyces cerevisiae* (expressed in E. coli), NMR Structure**	2K5U	Liu et al. (2009)
*ADP-ribosylation factor (ARF1GTP), myristoylated: Saccharomyces cerevisiae (expressed in E. coli), NMR Structure**	2KSQ	Liu et al. (2010)
Isomerases
*RPE65 visual cycle retinoid isomerase: Bos taurus, 2.14 Å* This retinal pigment epithelium (RPE) protein simultaneously cleaves and isomerizes all-trans-retinyl esters to 11-cis-retinol and a fatty acid.	3FSN	Kiser et al. (2009)
TRANSMEMBRANE PROTEINS: BETA-BARREL
Beta-Barrel Membrane Proteins: Multimeric (Porins and Relatives)
*Porin: Rhodobacter capsulatus, 1.8 Å*	2POR	Weiss & Schulz (1992)
*Porin: Rhodopeudomonas blastica, 1.96 Å*	1PRN	Kreusch et al. (1994)
*OmpK36 osmoporin: Klebsiella pneumoniae, 3.2 Å*	1OSM	Dutzler et al. (1999)
*Omp32 anion-selective porin: Comamonas acidovorans, 2.1 Å*	1E54	Zeth et al. (2000)
*Omp32 anion-selective porin: Delftia acidovorans, 1.5 Å* With bound malate, 1.45 Å: 2FGQ	2FGR	Zachariae et al. (2006)
*OmpF Matrix Porin: Escherichia coli, 2.4 Å* Note: Also see BtuB with bound colicin E3 R-domain, below.	2OMF	Cowan et al. (1992)
*OmpF Matrix Porin: Escherichia coli, 1.6 Å* With inserted 83 residue N-terminal peptide of colicin E3, 3.0 Å: 2ZLD	2ZFG	Yamashita et al. (2008)
*OmpF Matrix Porin in complex with colicin peptide OBS1: Escherichia coli, 3.01 Å* Shows colicin bound within porin lumen spanning the membrane bilayer	3O0E	Housden et al. (2010)
*OmpC Osmoporin: Escherichia coli, 2.0 Å*	2J1N	Baslé et al. (2006)
*OmpG monomeric* porin: Escherichia coli, 2.3 Å**	2F1C	Subbarao and van den Berg (2006)
*OmpG monomeric* porin in open state: Escherichia coli, 2.3 Å** OmpG in closed state, 2.73 Å: 2IWW	2IWV	Yildiz et al. (2006)
*OmpG monomeric* porin: Escherichia coli, NMR Structure (DPC micelles)**	2JQY	Liang & Tamm (2007)
*PhoE: Escherihia coli, 3.0 Å*	1PHO	Cowan et al. (1992)
*LamB Maltoporin: Salmonella typhimurium, 2.4 Å*	2MPR	Meyer et al. (1997)
*LamB Maltoporin: Escherichia coli, 3.1 Å*	1MAL	Schirmer et al. (1995)
*LamB Maltoporin in complex with maltose: Escherichia coli, 2.6 Å* In complex with maltotriose, 3.20 Å: 1MPN In complex with maltohexaose, 2.80 Å: 1MPO	1MPM	Dutzler et al. (1996)
*LamB Maltoporin in complex with sucrose: Escherichia coli, 2.4 Å* In complex with trehalose, 3.0 Å: 1MPQ	1AF6	Wang et al. (1997)
*ScrY sucrose-specific porin: Salmonella typhimurium, 2.4 Å* Complexed Form, 1A0T. Uncomplexed form, 1A0S.	1A0T	Forst et al. (1998)
*MspA mycobacterial porin: Mycobacterium smegmatis, 2.5 Å* Homooctamer	1UUN	Faller et al. (2004)
*OprP phosphate-specific transporter: Pseudomonas aeruginosa, 1.9 Å* Contains a novel nine-residue arginine ladder	2O4V	Moraes et al. (2007)
*OprD basic amino acid uptake channel: Pseudomonas aeruginosa, 2.9 Å* Like OprP, contains a basic ladder	2ODJ	Biswas et al. (2007)
*OpdK hydrocarbon transporter: Pseudomonas aeruginosa, 2.8 Å* Binds vanillate. Forms labile trimer.	2QTK	Biswas et al. (2008)
*PorB outer membrane protein, native structure: Neisseria meningitidis* (expressed in E. coli), 2.30 Å** The second most common OMP of Neisseria, PorB is required for pathogenesis. In complex with sucrose, 2.20 Å: 3A2S In complex with galactose, 3.20 Å: 3A2T In complex with AMP-PNP, 2.90 Å: 3A2U	3A2R	Tanabe et al. (2010)
Beta-Barrel Membrane Proteins: Monomeric/Dimeric
*TolC outer membrane protein: Escherichia coli, 2.1 Å* NOTE: Functional protein is a homotrimer. Each monomer contributes 4 strands to a single barrel.	1EK9	Koronakis et al.(2000)
*TolC outer membrane protein, ligand blocked: Escherichia coli, 2.75 Å*	1TQQ	Higgins et al.(2004)
*TolC outer membrane protein (Y362F, R367E), partially open state: Escherichia coli, 3.2 Å* 2VDE is P2₁2₁2₁ form. C2 form, 3.30 Å: 2VDD	2VDE	Bavro et al.(2008)
*VceC outer membrane protein: Vibrio cholerae, 1.8 Å* NOTE: Functional protein is a homotrimer. Each monomer contributes 4 strands to a single barrel.	1YC9	Federici et al. (2005)
*OprM drug discharge outer membrane protein: Pseudomonas aeruginosa, 2.56 Å* NOTE: Functional protein is a homotrimer. Each monomer contributes 4 strands to a single barrel. H32 space group.	1WP1	Akama et al. (2004)
*CusC heavy metal discharge outer membrane protein: Escherichia coli, 2.30 Å* NOTE: Functional protein is a homotrimer. Each monomer contributes 4 strands to a single barrel. H32 space group.	3PIK	Kulathila et al. (2011)
*CusBA heavy-metal efflux complex outer membrane protein: Escherichia coli, 2.90 Å* CusA, present as a trimer, interacts with six CusB protomers. The CusA trimer is an inner-membrane protein. The CusB hexamer spans the periplasmic space to interact with CusC.	3NE5	Su et al. (2011)
*BenF-like Porin (putative): Pseudomonas fluorescens, 2.60 Å*	3JTY	Sampathkumar et al. (2010)
*OprM drug discharge outer membrane protein: Pseudomonas aeruginosa* (expressed in E. coli), 2.40 Å** Structure of OprM in a non-symmetrical space group, P2₁2₁2₁	3D5K	Phan et al. (2010)
*apo BtuB cobalamin transporter: Escherichia coli, 2.0 Å* Related structures: 1NQF (SeMet-BtuB), 1NQG (Ca²⁺-BtuB), 1NQH (Ca²⁺-B₁₂-BtuB).	1NQE	Chimento et al.(2003)
*BtuB with bound colicin E3 R-domain: Escherichia coli, 2.75 Å* NOTE: The 135-residue coiled-coil R-domain is believed to deliver the colicin to OmpF (above).	1UJW	Kurisu et al. (2003)
*apo BtuB by in meso* crystallization: Escherichia coli, 1.95 Å** NOTE: Crystals were prepared from cubic phase lipids. This is the first β-barrel protein prepared by this method.	2GUF	Cherezov et al. (2006)
*BtuB in complex with TonB: Escherichia coli, 2.1 Å*	2GSK	Shultis et al. (2006)
*BtuB with bound colicin E2 R-domain: Escherichia coli, 3.50 Å*	2YSU	Sharma et al. (2007)
*Colicin I receptor Cir in complex with Colicin Ia binding domain: Escherichia coli, 2.5 Å* Cir Colicin I receptor alone, 2.65 Å: 2HDF	2HDI	Buchanan et al. (2007)
*OmpA: Escherichia coli, x-ray diffraction, 2.5 Å*	1BXW	Pautsch & Schulz (1998)
*OmpA: Escherichia coli, x-ray diffraction, 1.6 Å*	1QJP	Pautsch & Schulz (2000)
*OmpA: Escherichia coli, NMR (in DPC micelles)*	1G90	Arora et al. (2001)
*OmpA with four shortened loops: Escherichia coli, NMR (in DHPC micelles)* Called β-barrel platform (BBP)	2JMM	Johansson et al. (2007)
*OmpT outer membrane protease: Escherichia coli, 2.6 Å*	1I78	Vandeputte-Rutten et al. (2001)
*Pla Plasminogen activator (native 1): Yersinia pestis* (Expressed in E. coli), 1.90 Å** Wild-type (Native 2), 2.30 Å: 2X56 D86A mutant, 2.55 Å: 2X4M	2X55	Eren et al.(2010)
*OmpW outer membrane protein: Escherichia coli, 2.7 Å* 2F1V is orthorhomibic form. Trigonal form, 3.0 Å: 2F1T	2F1V	Hong et al. (2006)
*OprG outer membrane protein: Pseudomonas aeruginosa* (expressed in E. coli), 2.4 Å** Potential channel for hydrophobic molecule transport	2X27	Touw et al. (2010)
*OmpX: Escherichia coli, 1.9 Å* Structure at 2.1 Å, 1QJ9	1QJ8	Vogt & Schulz (1999)
*OmpX: Escherichia coli, NMR (DHPC micelles)*	1ORM	Fernández et al. (2001)
*OmpX: Escherichia coli, NMR (DPC micelles, with H-bond constraints)* For structure without H-bond constraints, see 1Q9G	1Q9F	Fernández et al. (2004)
*TtoA Outer Membrane Protein (OMP): Thermus thermophilus* HB27, 2.8 Å** First structure of an OMP from a thermophile	3DZM	Brosig et al. (2009)
*OmpLA (PldA) outer membrane phospholipase A monomer: Escherichia coli, 2.17 Å* Dimer, 2.10 Å: 1QD6	1QD5	Snijder et al.(1999)
*OmpLA (PldA) outer membrane phospholipase A monomer with Ca⁺⁺: Escherichia coli, 2.60 Å* Dimer, 2.80 Å: 1FW3	1FW2	Snijder et al.(2001)
*OmpLA (PldA) active-site mutant (N156A), pH 6.1: Escherichia coli, 2.50 Å* pH 4.6, 2.80 Å: 1ILD pH 8.3, 2.98 Å: 1IM0	1ILZ	Snijder et al.(2001)
*OpcA adhesin protein: Neisseria meningitidis, 2.0 Å*	1K24	Prince et al. (2002)
*NspA surface protein: Neisseria meningitidis, 2.55 Å*	1P4T	Vandeputte-Rutten et al. (2003)
*NalP autotransporter translocator domain: Neisseria meningitidis, 2.60 Å* p6₁22 space group. See also 1UYO, C222₁ space group, 3.2 Å resolution.	1UYN	Oomen et al.(2004)
*NanC Porin, model for KdgM porin family: Escherichia coli, 1.80 Å* H3 space group. See also 2WJQ, p6₃22 space group, 2.0 Å resolution.	2WJR	Wirth et al.(2009)
*Hia_1022-1098 trimeric autotransporter: Haemophilus influenzae, 2.0 Å* Hia_992-1098, 2.3 Å: 2GR7	2GR8	Meng et al. (2006)
*EspP autotransporter, postcleavage state: Escherichia coli, 2.7 Å*	2QOM	Barnard et al. (2007)
*EstA Autotransporter, full length: Pseudomonas aeruginosa* (expressed in E. coli), 2.50 Å** This is the first full-length structure of an autotransporter	3KVN	van den Berg (2010)
*PagP outer membrane palimitoyl transferease: Escherichia coli, NMR* 1MM4 is Structure in DPC micelles. Structure in OG micelles: 1MM5	1MM4	Hwang et al. (2002)
*PagP outer membrane palimitoyl transferease: Escherichia coli, x-ray, 1.9 Å*	1THQ	Ahn et al. (2004)
*PagP outer membrane palimitoyl transferease crystallized from SDS/Co-solvent: Escherichia coli, x-ray, 1.4 Å* Reveals phospholipid access route (crenel between strands F and G)	3GP6	Cuesta-Seijo et al. (2010)
*FadL long-chain fatty acid transporter: Escherichia coli, 2.6 Å* 1T16 is from Monoclinic crystals. From hexagonal crystals, 2.8 Å: 1T1L	1T16	van den Berg et al. (2004)
*FadL long-chain fatty acid transporter A77E/S100R mutant: Escherichia coli, 2.5 Å* Mutants show that channel wall opening for passage of fatty acids into inner layer of outer membrane is likely. ΔS3 kink, 2.60 Å: 2R88 P34A mutant, 3.3 Å: 2R4L N33A mutant, 3.2 Å: 2R4N ΔNPA mutant, 3.6 Å: 2R4O G212E mutant, 2.9 Å: 2R4P	3DWN	Hearn et al. (2009)
*FadL homologue long-chain fatty acid transporter: Pseudomonas aeruginosa* (expressed in E. coli), 2.2 Å** Shows break in channel wall for passage of fatty acids into inner layer of outer membrane in a species other than E. coli. Residues 22-463.	3DWO	Hearn et al. (2009)
*FauA alcaligin outer membrane transporter: Bordetella pertusssis* (expressed in E. coli), 2.3 Å**	3EFM	Brillet et al. (2009)
*TodX hydrocarbon transporter: Pseudomonas putida, 2.6 Å* 3BS0 is P1 space group, 2 molecules in asymmetric unit. I222 space group, 3.2 Å: 3BRZ	3BS0	Hearn et al. (2008)
*TbuX hydrocarbon transporter: Ralstonia pickettii, 3.2 Å*	3BRY	Hearn et al. (2008)
*Tsx nucleoside transporter (apoprotein): Eschericia coli, 3.0 Å* Protein + thymidine, 3.10 Å: 1TLW Protein + uridine, 3.10 Å: 1TLZ	1TLY	Ye and van den Berg (2004)
*FhuA, Ferrichrome-iron receptor without ligand: Escherichia coli, 2.7 Å* With ligand: 1BY5	1BY3	Locher et al. (1998)
*FhuA: Escherichia coli, 2.5 Å* FhuA-ferrichrome-iron complex, 2.7 Å: 1FCP	2FCP	Ferguson et al. (1998)
*FhuA-AW140-LPS: Escherichia coli, 2.5 Å* Structure of lipopolysaccharide (LPS) in complex with FhuA. FhuA-DL41-LPS-ferricrocin, 2.7 Å: 1QFF	1QFG	Ferguson et al. (2000)
*FhuA in complex with albomycin: Escherichia coli, 3.10 Å* In complex with phenylferricrocin, 2.95 Å: 1QJQ	1QKC	Ferguson et al. (2000)
*FhuA in complex with lipopolysaccharide and rifamycin CGP4832: Escherichia coli, 2.90 Å*	1FI1	Ferguson et al. (2001)
*FhuA in complex withTonB: Escherichia coli, 3.3 Å*	2GRX	Pawelek et al. (2006)
*FepA, Ferric enterobactin receptor: Escherichia coli, 2.4 Å*	1FEP	Buchanan et al. (1999)
*FecA, siderophore transporter: Escherichia coli, 2.0 Å* Structure at 2.5 Å: 1KMP	1KMO	Ferguson et al. (2002)
*FecA, siderophore transporter (no ligand): Escherichia coli, 2.5 Å* FecA with iron-free dicitrate, 2.15 Å: : 1PO0 FecA with diferric dicitrate, 3.4 Å: : 1PO3	1PNZ	Yue et al. (2003)
*FecA, siderophore transporter periplasmic signalling domain: Escherichia coli, NMR Structure* Shows the signalling domain not seen x-ray structures	2D1U	Garcia-Herrero & Vogel (2005)
*HasR heme-uptake receptor in complex with HasA hemophore and heme: Serratia marcescens* (expressed in E. coli), 2.7 Å** HasA~HasR, 3.0 Å: 3CSN HasA~HasR[I671G]~heme, 2.8 Å: 3DDR	3CSL	Krieg et al. (2009)
*FptA, pyochelin outer membrane receptor: Pseudomonas aeruginosa, 2.0 Å*	1XKW	Cobessi et al. (2005)
*FpvA, Pyoverdine receptor: Pseudomonas aeruginosa, 3.6 Å*	1XKH	Cobessi et al. (2005)
*FpvA, Pyoverdine receptor (apo form): Pseudomonas aeruginosa, 2.77 Å*	2O5P	Brillet et al. (2007)
*FpvA, Full-length structure bound to iron-pyoverdine: Pseudomonas aeruginosa, 2.73 Å*	2IAH	Wirth et al. (2007)
*P pilus usher translocation domain, PapC_130-640: Escherichia coli, 3.2 Å*	2VQI	Remaut et al. (2008)
Beta-Barrel Membrane Proteins: Mitochondrial Outer Membrane
*VDAC-1 voltage dependent anion channel: Human* (expressed in E. coli), NMR structure** Structure determined in LDAO micelles.	2K4T	Hiller et al.(2008)
*VDAC-1 voltage dependent anion channel: Human (expressed in E. coli), 4 Å* Structure determined by combining x-ray and NMR data.	2JK4	Bayrhuber et al.(2008)
*VDAC-1 voltage dependent anion channel: Murine (expressed in E. coli), 2.3 Å* Reveals the voltage-sensing N-terminal α-helix.	3EMN	Ujwal et al.(2008)
Omp85-TpsB Outer Membrane Transporter Superfamily
*FhaC Filamentous Hemagglutinin Transporter: Bordetella pertussis, 3.15 Å* The first outer membrane protein from the Omp85–two-partner secretion B (TpsB) superfamily	2QDZ	Clantin et al. (2007)
*TeOmp85-N POTRA domains: Thermosynechococcus elongatus* (expressed in E. coli), 1.97 Å** Structure is of complete N-terminus containing three POTRA domains. The polypeptide transport-associated (POTRA) domains link to a transmembrane β-barrel, which is absent in this structure.	2X8X	Arnold et al. (2010)
*anaOmp85-N POTRA domains (hexagonal crystals): Anabaena sp.* PCC7120 (expressed in E. coli), 2.20 Å** Structure is of complete N-terminus containing three POTRA domains. The polypeptide transport-associated (POTRA) domains link to a transmembrane β-barrel, which is absent in this structure. Tetragonal crystals, 2.59 Å: 3MC8	3MC9	Koenig et al. (2010)
*BamA_21-351 POTRA domains (periplasmic fragment, P2₁2₁2₁): Escherichia coli, 2.2 Å* BamA was formerly named YaeT. The polypeptide transport-associated (POTRA) domains link to a transmembrane β-barrel, which is absent in this structure. P2₁2₁2 space group, 2.2 Å: 2QDF	2QCZ	Kim et al. (2007)
*BamA_21-410 POTRA domains (periplasmic fragment): Escherichia coli, 3.3 Å* BamA was formerly named YaeT. The polypeptide transport-associated (POTRA) domains link to a transmembrane β-barrel, which is absent in this structure. Structure shows the first four POTRA domains in an extended conformation.	3EFC	Gatzeva-Topalova et al. (2008)
*BamA_21-174 POTRA domains 1 and 2: Escherichia coli, NMR Structure* BamA was formerly named YaeT.	2V9H	Knowles et al. (2008)
*BamA_264-424 POTRA domains 4 and 5: Escherichia coli, 2.69 Å* BamA was formerly named YaeT. From this structure and earlier ones (above), Gatzeva-Topalova et al. have constructed a 'spliced' model for the complete POTRA1-5 structure.	3OG5	Gatzeva-Topalova et al. (2010)
*BamE component of the Bam β-barrel assembly machine: Escherichia coli, NMR structure*	2KM7	Knowles et al. (2011)
*BamB component of the Bam β-barrel assembly machine: Escherichia coli, 1.80 Å*	3PRW	Heuck et al. (2011)
*BamB component of the Bam β-barrel assembly machine: Escherichia coli, 2.60 Å*	3P1L	Kim & Paetzel (2011)
*BamB component of the Bam β-barrel assembly machine, I222 space group: Escherichia coli, 1.65 Å* P2₁2₁2₁ space group, 1.77 Å: 3Q7N P2₁3 space group, 2.09 Å: 3Q7O	3Q7M	Noinaj et al. (2011)
Non-constitutive. Beta-sheet Pore-forming Toxins
*Alpha-hemolysin: Staphylococcus aureus, 1.9 Å*	7AHL	Song et al. (1996)
*LukF: Staphylococcus aureus, 1.9 Å* NOTE: The structure is of the water soluble form of the protein. It is included here because it is similar to alpha-hemolysin in behavior, and may be taken as representative of the protomeric state of alpha-hemolysin. At 2.5 Å: 2LKF. With bound phosphocholine, 1.9 Å: 3LKF	1LKF	Olson et al. (1999)
*Perfringolysin O (PFO) protomer: Clostridium perfringens* (Expressed in E. coli), 2.20 Å** The protein is a thiol-activated cytolysin that uses membrane cholesterol as a receptor. 40 or more protomers assemble into a large pore anchored in the bilayer by the β-sheets of domain 4. Space group is C222₁. P2₁2₁2 space group, 3.0 Å: 1M3J. P3₁ space group, 2.90 Å: 1M3I.	1PFO	Rossjohn et al. (1997)
*Anthrax Protective Antigen (PA) and Lethal Factor (LF) Prechannel Complex: Bacillus anthraciss* (Expressed in E. coli), 3.10 Å** The structure is the PA₈LF₄ prechannel.	3KWV	Feld et al. (2010)
*Lymphocyte preforin monomer: Mus musculus* (Expressed in S. frugiperda), 2.75 Å** The multimeric pore structure has been visualized by cyo-EM.	3NSJ	Law et al. (2010)
TRANSMEMBRANE PROTEINS: ALPHA-HELICAL
Non-constitutive. Alpha-helical Pore-forming Toxins.
*Cytolysin A (ClyA, aka HlyE): Escherichia coli, 3.29 Å*	2WCD	Mueller et al. (2009)
*FraC eukaryotic pore-forming toxin from sea anemone: Actinia fragacea, 1.80 Å*	3LIM	Mechaly et al. (2011)
Outer Membrane Proteins
*Wza translocon for capsular polysaccharides: Escherichia coli, 2.25 Å* The first outer membrane protein that penetrates the membrane as an alpha-helix bundle. The intact protein is comprised of eight monomers.	2J58	Dong et al. (2006)
*Porin B monomer: Corynebacterium glutamicum* (expressed in Escherichia coli), 1.82 Å** Putative helical porin, probably comprised of five monomers. Crystal form I. Crystal form II, 2.89 Å: 2VQH Crystal form IV, 4.20 Å: 2VQK Crystal form III, 3.16 Å: 2VQL	2VQG	Ziegler et al. (2008)
*Type IV outer membrane secretion complex: Escherichia coli, 2.60 Å* Comprised of 14 copies each of TraF, TraO, and TraN; 590 kDa.	3JQO	Chandran et al. (2009)
Bacterial Rhodopsins
*Bacteriorhodopsin (BR): Halobacterium salinarium, electron diffraction, 3.5 Å* 2D Crystals. The first atomic-resolution structure of bacteriorhodopsin	2BRD	Grigorieff et al. (1996)
*Bacteriorhodopsin (BR): Halobacterium salinarium, electron diffraction, 3.0 Å* 2D Crystals	1AT9	Kimura et al. (1997)
*Bacteriorhodopsin (BR): Halobacterium salinarium, 2.35 Å* The first x-ray structure of bacteriorhodopsin	1AP9	Pebay-Peyroula et al. (1997)
*Bacteriorhodopsin (BR): Halobacterium salinarium, 2.90 Å*	1BRR	Essen et al. (1998)
*Bacteriorhodopsin (BR): Halobacterium salinarium, 2.30 Å*	1BRX	Luecke et al. (1998)
*Bacteriorhodopsin (BR), K intermediate: Halobacterium salinarium, 2.10 Å* R-free = O.255. R-free = 0.303, 2.1 Å: 1QKO	1QKP	Edman et al. (1999)
*Bacteriorhodopsin (BR), K intermediate (illuminated): Halobacterium salinarium, 1.43 Å* Non-illuminated, 1.47 Å: 1M0L	1M0K	Schobert et al. (2002)
*Bacteriorhodopsin (BR): Halobacterium salinarium, 1.90 Å*	1QHJ	Belrhali et al. (1999)
*Bacteriorhodopsin (BR): Halobacterium salinarium, 1.55 Å*	1C3W	Luecke et al. (1999)
*Bacteriorhodopsin (BR), D96N in bR state: Halobacterium salinarium, 1.80 Å* D96N in M-state, 2.00 Å: 1C8S.	1C8R	Luecke et al. (1999)
*Halorhodopsin (HR): Halobacterium salinarium, 1.8 Å*	1E12	Kolbe et al. (2000)
*Halorhodopsin (HR): Natronomonas pharaonis, 2.0 Å*	3A7K	Kouyama et al. (2010)
*Sensory Rhodopsin I (SRI): Anabaena (Nostoc) sp. PCC7120, 2.0 Å*	1XIO	Vogeley et al. (2004)
*Sensory Rhodopsin II (SRII): Natronomonas pharaonis, X-ray, 2.4 Å*	1JGJ	Luecke et al. (2001)
*Sensory Rhodopsin II (SRII): Natronomonas pharaonis, X-ray, 2.1 Å*	1H68	Royant et al. (2001)
*Sensory Rhodopsin II (SRII) with transducer: Natronomonas pharaonis, X-ray, 1.93 Å*	1H2S	Gordeliy et al. (2002)
*Sensory Rhodopsin II (SRII): Natronomonas pharaonis, NMR structure*	2KSY	Gautier et al. (2010)
*Archaerhodopsin-1 (aR-1): Halorubrum sp. aus-1, 3.4 Å*	1UAZ	Enami et al. (2006)
*Archaerhodopsin-2 (aR-2): Haloroubrum sp. aus-2* , 2.5 Å**	1VGO	Enami et al. (2006)
*Archaerhodopsin-2 (aR-2): Haloroubrum sp. aus-2* , 2.10 Å** Crystallized with the carotenoid bacterioruberin, space group P321. Space group P6₃, 2.50 Å: 2Z55.	2EI4	Yoshimura & Kouyama. (2008)
*Xanthorhodopsin: Salinibacter ruber, 1.9 Å* Contains bound carotenoid.	3DDL	Luecke et al. (2008)
G Protein-Coupled Receptors (GPCRs)
*Rhodopsin: Bovine Rod Outer Segment (Bos taurus), 2.8 Å.* See also 1HZX and RPE65 retinoid isomerase	1F88	Palczewski et al. (2000)
Rhodopsin: Bovine Rod Outer Segment, 2.6 Å	1L9H	Okada et al. (2002)
Rhodopsin: Bovine Rod Outer Segment, 2.65 Å	1GZM	Li et al. (2004)
Rhodopsin: Bovine Rod Outer Segment, 2.2 Å	1U19	Okada et al. (2004)
Rhodopsin: Bovine Rod Outer Segment (expressed in COS cells), 3.4 Å Recombinant rhodopsin mutant, N2C/D282C	2J4Y	Standfuss et al. (2007)
Rhodopsin, photoactivated: Bovine Rod Outer Segment, 4.15 Å Ground state, rhombohedral crystals, 3.8 Å 2I35. Ground state, trigonal crystals, 4.1 Å 2I36.	2I37	Salom et al. (2006)
Rhodopsin in ligand-free state (opsin): Bovine Rod Outer Segment, 2.9 Å 2 molecules in asymmetric unit.	3CAP	Park et al. (2008)
Rhodopsin in Meta II state: Bovine Rod Outer Segment, 3.00 Å Metarhodopsin II in complex with C-terminal fragment of Gα (GαCT2), 2.85 Å: 3PQR	3PXO	Choe et al. (2011)
*Rhodopsin, Ops-GαCT peptide complex: Bovine Rod Outer Segment, 3.2 Å**	3DQB	Scheerer et al. (2008)
*Rhodopsin: Squid (Todarodes pacificus), 2.5 Å*	2Z73	Murakami & Kouyama (2008)
*Rhodopsin: Squid (Todarodes pacificus), 3.7 Å* Shows intracellularly extended cytoplasmic region.	2ZIY	Shimamura et al. (2008)
*β₁ adrenergic receptor (engineered): Meleagris gallopavo* (turkey) (expressed in Trichoplusia ni), 2.7 Å**	2VT4	Warne et al. (2008)
*β₁ adrenergic receptor (engineered) with bound dobutamine: Meleagris gallopavo* (turkey) (expressed in Trichoplusia ni), 2.50 Å** With bound dobutamine, 2.65 Å:2Y01 With bound carmoterol, 2.65 Å:2Y02 With bound isoprenaline, 2.85 Å:2Y03 With bound salbutamol, 3.05 Å:2Y04	2Y00	Warne et al. (2011)
*β₂ adrenergic receptor: Homo sapiens* (Expressed in Spodoptera frugiperda), 3.4/3.7 Å** from β₂AR365-Fab5 complex. From β₂AR24/365-Fab5 complex: 2R4S	2R4R	Rasmussen et al. (2007)
*Methylated β₂ adrenergic receptor: Homo sapiens* (Expressed in S. frugiperda), 3.4 Å** from β₂AR365-Fab5 complex.	3KJ6	Bokoch et al. (2010)
*β₂ adrenergic receptor (engineered): Homo sapiens* (Expressed in S. frugiperda), 2.4 Å** T4 lysozyme replaces third intracellular loop. Reveals close association with cholesterol.	2RH1	Cherezov et al. (2007)
*β₂ adrenergic receptor (engineered): Homo sapiens* (Expressed in S. frugiperda), 2.8 Å** T4 lysozyme replaces third intracellular loop. Reveals specific cholesterol binding site.	3D4S	Hanson et al. (2008)
*β₂ adrenergic receptor (engineered) in nanobody-stabilized active state: Homo sapiens* (Expressed in S. frugiperda), 3.50 Å** T4 lysozyme replaces third intracellular loop. The nanobody Nb80 is an intact antigen-binding domain of a camelid heavy-chain antibody.	3P0G	Rasmussen et al. (2011)
*β₂ adrenergic receptor (engineered) with irreversibly-bound agonist: Homo sapiens* (Expressed in S. frugiperda), 3.50 Å** T4 lysozyme replaces third intracellular loop. The agonist is covalently linked to the receptor by a disulphide bond.	3PDS	Rosenbaum et al. (2011)
*A_2A adenosine receptor: Homo sapiens* (Expressed in S. frugiperda), 2.6 Å** In complex with a high-affinity subtype-selective antagonist ZM241385.	3EML	Jaakola et al. (2008)
*A_2A adenosine receptor with bound agonist (UK-432097): Homo sapiens* (Expressed in S. frugiperda), 2.71 Å** Reveals structural changes in helices III, V, & VI relative to inactive, antagonist-bound form. Engineered protein: T4 lysozyme inserted between TM helices V and VI.	3QAK	Xu et al. (2011)
*CXCR4 Chemokine Receptor Complexed with IT1t Antagonist: Homo sapiens* (Expressed in S. frugiperda), 2.5 Å** Engineered protein: T4 lysozyme inserted between TM helices V and VI. P2₁ space group. CXCR4 with IT1t (P1 space group), 3.10 Å: 3OE8 CXCR4 with IT1t (P1 space group), 3.10 Å: 3OE9 CXCR4 with IT1t (I222 space group), 3.20 Å: 3OE6 CXCR4 with cyclic peptide antagonist CVX15 (C2 space group), 2.90 Å: 3OE0	3ODU	Wu et al. (2010)
*Dopamine D3 Receptor Complexed with D2/D3-selective Antagonist: Homo sapiens* (Expressed in S. frugiperda), 2.89 Å** Engineered protein: T4 lysozyme inserted between TM helices V and VI.	3PBL	Chien et al. (2010)
Autonomously Folding "Membrane Proteins" (Sec-independent)
*Mistic membrane-integrating protein: Bacillus subtilis, NMR structure* Note: This is not a constitutive membrane protein. It is included here because of general interest.	1YGM	Roosild et al. (2005)
Glycoproteins
*Glycophorin A transmembrane-domain dimer: Homo sapiens* (expressed in E. coli), NMR Structure**	1AFO	MacKenzie et al. (1997)
SNARE Protein Family
*Syntaxin 1A/SNAP-25/Synaptobrevin-2 Complex with transmembrane regions: ratus ratus* (expressed in E. coli), 3.4 Å** I2₁2₁2₁ space group, 4.80 Å: 3HD9.	3HD7	Stein et al. (2009)
Integrin Adhesion Receptors
*Human Integrin αIIbβ3 transmembrane-cytoplasmic heterodimer: Homo sapiens* (expressed in E. coli), NMR Structure**	2KNC	Yang et al. (2009)
Histidine Kinase Receptors
*ArcB (1-115) Aerobic Respiration Control sensor membrane domain: Escherichia coli* (cell-free expression), NMR Structure**	2KSD	Maslennikov et al. (2010)
*QseC (1-185) Sensor protein membrane domain: Escherichia coli* (cell-free expression), NMR Structure**	2KSE	Maslennikov et al. (2010)
*KdpD (397-502) Sensor protein membrane domain: Escherichia coli* (cell-free expression), NMR Structure**	2KSF	Maslennikov et al. (2010)
Immune Receptors
*Transmembrane ζ-ζ dimer of the TCR-CD3 complex: Homo sapiens* (expressed in E. coli), NMR Structure**	2HAC	Call et al. (2006)
*DAP12 dimeric signaling domain in complex with activating receptor NKG2C: Homo sapiens* (expressed in E. coli), NMR Structure** DAP12 dimer: 2L34	2L35	Call et al. (2010)
Channels: Potassium and Sodium Ion-Selective (more information)
*KcsA Potassium channel, H⁺ gated: Streptomyces lividans* (expressed in E. coli), 3.2 Å**	1BL8	Doyle et al. (1998)
*KcsA Potassium channel, H⁺ gated: Streptomyces lividans* (expressed in E. coli), 2.0 Å** R-free = 0.233. 1K4D, 2.3 Å, R-free = 0.235	1K4C	Zhou et al. (2001)
*Full-length KcsA Potassium channel, H⁺ gated: Streptomyces lividans* (expressed in E. coli), 3.80 Å** Crystallized with synthetic Fab2 antibodies. C-terminal domain alone (residues 129-158) crystallized with synthetic Fab4 antibodies 3EFD, 2.60 Å	3EFF	Uysal et al. (2009)
*KcsA Potassium channel in the presence of 150 mM Li⁺ and 3 mM K⁺: Streptomyces lividans* (expressed in E. coli), 2.75 Å** KcsA in the presence of 150 mM Li⁺ and 0 mM K⁺, 2.85 Å: 3GB7	3IGA	Thompson et al. (2009)
*KcsA Potassium channel in the open inactivated state. Open 32 Å conformer: Streptomyces lividans* (expressed in E. coli), 3.30 Å** Open 23 Å conformer, 3.20 Å: 3F7V Open 17 Å conformer, 3.40 Å: 3F7Y Open 16 Å conformer, 3.00 Å: 3FB6 Open 14.5 Å conformer, 2.80 Å: 3FB5	3F5W	Cuello et al. (2010)
*KcsA Potassium channel E71H-F103A inactivated-state mutant (closed state): Streptomyces lividans* (expressed in E. coli), 3.20 Å** KcsA open-state in the presence of Rb⁺, 3.30 Å: 3FB7	3HPL	Cuello et al. (2010)
*KcsA Potassium channel E71I modal-gating mutant: Streptomyces lividans* (expressed in E. coli), 2.30 Å** E71Q mutant, 2.70 Å: 3OR6	3OR7	Chakrapani et al. (2011)
*KvAP Voltage-gated potassium Channel in complex with Fab: Aeropyrum pernix* (Expressed in E. coli), 3.2 Å** Voltage sensor domain, 1.9 Å: 1ORS	1ORQ	Jiang et al (2003) Crystal structures. Jiang et al (2003) Voltage sensor mechanism.
*KvAP Voltage-gated potassium Channel in complex with Fv fragments: Aeropyrum pernix* (Expressed in E. coli), 3.9 Å**	2A0L	Lee et al. (2005)
*KvAP Voltage-Sensing Domain in phospholipid micelles: Aeropyrum pernix* (Expressed in E. coli), NMR Structure**	2KYH	Butterwick & MacKinnon (2010)
*Kv1.2 Voltage-gated potassium Channel: Rattus norvegicus* (expressed in Pichia pastoris), 2.9 Å**	2A79	Long et al. (2005a) Long et al. (2005b)
*Kv1.2 Voltage-gated potassium Channel (full length): Rattus norvegicus* (expressed in Pichia pastoris), 2.9 Å** Re-refinement of 2A79 above using normal-mode x-ray crystallographic refinement	3LUT	Chen et al. (2010)
*Kv1.2/Kv2.1 Voltage-gated potassium channel chimera: Rattus norvegicus* (expressed in Pichia pastoris), 2.4 Å** First Kv channel with resolved lipids.	2R9R	Long et al. (2007)
*Kv1.2/Kv2.1 Voltage-gated potassium channel chimera: Rattus norvegicus* (expressed in Pichia pastoris), 2.9 Å** F233W Mutant.	3LNM	Tao et al. (2010)
*MthK Potassium channel, Ca⁺⁺ gated: Methanothermobacter thermautotrophicus* (expressed in E. coli), 3.3 Å**	1LNQ	Jiang et al. (2002) Crystal structure and mechanism. Jiang et al. (2002) Open pore conformation.
*K⁺ pore of the MthK Potassium channel (residues 28-99): Methanothermobacter thermautotrophicus* (expressed in E. coli), 1.45 Å** 3LDC crystallized in 100 mM KCl. S68H/V77C mutant. 99 mM NaCl + 1 mM KCl; S68R, V77C mutant; 1.45 Å: 3LDD 100 mM NaCl; S68H, V77C mutant; 2.21 Å: 3LDE	3LDC	Ye et al. (2010)
*Human BK Channel Ca²⁺-activation apparatus: Homo sapiens* (expressed in S. frugiperda), 3.0 Å** Consists of four BK subunits organized as a ring of 8 RCK (Regulator of K⁺ conductance) domains. Although not a transmembrane protein, it is an important accessory structure for regulating voltage-gated potassium channels.	3MT5	Yuan et al. (2010)
*Human BK Channel Ca²⁺-activation apparatus: Homo sapiens* (expressed in S. frugiperda), 3.1 Å** Consists of four BK subunits organized as a ring of 8 RCK (Regulator of K⁺ conductance) domains. Although not a transmembrane protein, it is an important accessory structure for regulating voltage-gated potassium channels.	3NAF	Wu et al. (2010)
*Kir3.1-Prokaryotic Kir Chimera: Mus musculus & Burkholderia xenovornas* (expressed in Escherichia coli), 2.2 Å**	2QKS	Nishida et al (2007)
*Kir3.1 cytoplasmic domain: Mus musculus* (expressed in E. coli), 2.0 Å**	3K6N	Xu et al (2009)
*Kir2.2 Inward-Rectifier Potassium Channel (Complete): Gallus gallus* (expressed in Pichia pastoris), 3.1 Å**	3JYC	Tao et al (2009)
*KirBac1.1 Inward-Rectifier Potassium channel (closed state): Burkholderia pseudomallei, 3.65 Å* For re-refined structure, see 2WLL	1P7B	Kuo et al (2003)
*KirBac3.1 Inward-Rectifier Potassium channel (semi-latched): Magnetospirillum magnetotacticum* (expressed in E. coli), 2.60 Å** (Re-refinement of 1XL4) Latched State, 2.80 Å: 2WLK (re-refinement of 1XL6) Semi-latched State, 3.09 Å: 2WLI Semi-latched State, 4.20 Å: 2WLO Semi-latched State, 3.61 Å: 2WLM Unlatched State, 3.44 Å: 2WLN Unlatched State, 3.28 Å: 2WLH Q170A mutant (stalled), 3.10 Å: 2X6A Q170A mutant (blocked with Ba⁺⁺), 3.30 Å: 2X6B Q170A mutant (conductive), 2.70 Å: 2X6C	2WLJ	Clarke et al. (2010)
*MlotiK1 cyclic nucleotide-regulated K⁺-channel: Mesorhizobium loti* (expressed in E. coli), 3.1 Å**	3BEH	Clayton et al. (2008)
*mGIRK1 G-Protein Gated Inward Rectifying Potassium Channel: Mus musculus, 1.8 Å* NOTE: This is not strictly an integral membrane protein, because it is the cytoplasmic channel domain located external to the membrane. It is included here for completeness.	1N9P	Nishida & MacKinnon (2002)
*NaK channel (Na⁺complex): Bacillus cereus* (expressed in E. coli), 2.4 Å** K⁺ complex, 2.8 Å: 2AHZ.	2AHY	Shi et al. (2006)
*NaK channel with bound calcium, D66A mutant: Bacillus cereus* (expressed in E. coli), 2.30 Å** D66A/S70E mutant, 2.50 Å: 2Q68. D66N mutant, 2.40 Å: 2Q69. D66E mutant, 2.60 Å: 2Q6A.	2Q67	Alam et al. (2007)
*NaK channel in open state (NΔ19 mutant): Bacillus cereus* (expressed in E. coli), 1.60 Å**	3E86	Alam & Jiang (2009)
*CNG-mimicking NaK channel mutant; NaK-ETPP/K⁺ complex: Bacillus cereus* (expressed in E. coli), 1.95 Å** CNG-mimicking mutant; NaK-NTPP/K⁺ complex, 1.58 Å: 3K06 CNG-mimicking mutant; NaK-ETPP/Na⁺ complex, 1.95 Å: 3K0G CNG-mimicking mutant; NaK-DTPP/Na⁺ complex, 1.58 Å: 3K04 CNG-mimicking mutant; NaK-NTPP/Na⁺ complex, 1.62 Å: 3K08	3K0D	Derebe et al. (2011)
*NaK channel; K⁺ selective mutant: Bacillus cereus* (expressed in E. coli), 1.55 Å** CNG-mimicking mutant; NaK-DTPP/K⁺ complex, 1.62 Å: 3K03 MthK channel T59A mutant, 1.75 Å: 3OUS	3OUF	Derebe et al. (2011)
Channels: Other Ion Channels
*GluA2 Glutamate receptor (AMPA-subtype): Rattus norvegicus* (expressed in sf9 cells), 3.60 Å** 3KG2 is in complex with the competitive antagonist ZK 200775 GluA2 ligand-binding core complex with bound glutamate, 1.55 Å: 3KGC	3KG2	Sobolevsky et al. (2009)
M2 proton channel: Influenza A (synthesized), 2.05 Å with amantadine inhibitor, 3.50 Å: 3C9J	3BKD	Stouffer et al. (2008)
*M2 proton channel: Influenza A (expressed in E. coli), NMR structure* with rimantadine inhibitor	2RLF	Schnell & Chou. (2008)
*M2 proton channel in a hydrated lipid bilayer: Influenza A (expressed in E. coli), NMR structure*	2L0J	Sharma et al. (2010)
*M2 proton channel: Influenza B (expressed in Escherichia coli), NMR Structure* Cytoplasmic domain, NMR Structure: 2KJ1	2KIX	Wang et al. (2009)
*ASIC1 Acid-Sensing Ion Channel (ΔASIC1; N- and C-term deletions): Gallus gallus* (expressed in SF9 cells), 1.9 Å** Construct does not exhibit proton-dependent gating	2QTS	Jasti et al. (2007)
*ASIC1 Acid-Sensing Ion Channel (ASIC1mfc; minimal functional channel): Gallus gallus* (expressed in SF9 cells), 3.0 Å** Desensitized State	3HGC	Gonzales et al. (2009)
*ATP-gated P2X₄ ion channel (apo protein): Danio rerio* (zebra fish) (expressed in SF9 cells), 3.1 Å** Closed state. A construct, 3.5 Å: 3I5D	3H9V	Kawate et al. (2009)
*Nicotinic Acetylcholine Receptor Pore (closed state): Torpedo marmorata, electron diffraction, 4.0 Å*	1OED	Miyazawa et al. (2003)
*Nicotinic Acetylcholine Receptor, refined structure: Torpedo marmorata, electron diffraction, 4.0 Å*	2BG9	Unwin (2005)
*Prokaryotic pentameric ligand-gated ion channel (pLGIC): Erwinia chrysanthemi* (expressed in E. coli), 3.3 Å** First high-resolution x-ray structure of an AChR-like channel.	2VL0	Hilf & Dutzler (2008)
*Prokaryotic pentameric ligand-gated ion channel (GLIC): Gloebacter violaceus* (expressed in E. coli), 3.1 Å** Related to pLGIC (above), this pentameric channel is apparently in an open state. E221A mutant, 3.50 Å: 3EI0	3EHZ	Hilf & Dutzler (2009)
*Prokaryotic pentameric ligand-gated ion channel (GLIC): Gloebacter violaceus* (expressed in E. coli), 2.9 Å** Related to pLGIC (above), this pentameric channel is apparently in an open state.	3EAM	Bocquet et al. (2009)
*Prokaryotic "pentameric" ligand-gated ion channel (GLIC) with hexameric quaternary structure: Gloebacter violaceus* (expressed in E. coli), 2.3 Å**	3IGQ	Nury et al. (2010)
*Prokaryotic pentameric ligand-gated ion channel (GLIC), wildtype-TBSb complex: Gloebacter violaceus* (expressed in E. coli), 3.70 Å** Wildtype-TEAs complex, 3.50 Å: 2XQ5 E221D-TEAs complex, 3.20 Å: 2XQ9 Wildtype-TMAs complex, 3.60 Å: 2XQ4 Wildtype-bromo-lidocaine complex, 3.50 Å: 2XQ3 Wildtype-Cd²⁺ complex, 3.40 Å: 2XQ7 Wildtype-Zn²⁺ complex, 3.60 Å: 2XQ8 Wildtype-Cs⁺ complex, 3.70 Å: 2XQ6	2XQA	Hilf et al. (2010)
*Prokaryotic pentameric ligand-gated ion channel (GLIC) in complex with propofol anesthetic: Gloebacter violaceus* (expressed in E. coli), 3.30 Å** In complex with desflurane, 3.20 Å: 3P4W	3P50	Nury et al. (2011)
*MscL Mechanosensitive channel: Mycobacterium tuberculosis, 3.5 Å*	2OAR	Chang et al. (1998)
*MscL Mechanosensitive channel, Δ95-120: Staphylococcus aureus, 3.8 Å* Shows MscL in an expanded intermediate state.	3HZQ	Liu et al. (2009)
*MscS voltage-modulated mechanosensitive channel: Escherichia coli, 3.7 Å*	2OAU	Bass et al. (2002)
*MscS mechanosensitive channel in the open form: Escherichia coli, 3.45 Å*	2VV5	Wang et al. (2008)
*CorA Mg²⁺ Transporter: Thermotoga maritima, 3.9 Å* Soluble domain, 1.85 Å. 2BBH	2BBJ	Lunin et al. (2006)
*CorA Mg²⁺ Transporter: Thermotoga maritima, 2.9 Å*	2IUB	Eshaghi et al. (2006)
*MgtE Mg²⁺ Transporter: Thermus thermophilus* (expressed in E. coli), 3.5 Å** Cytoplasmic domains w. bound Mg²⁺, 2.30 Å: 2YVY Cytoplasmic domains without Mg²⁺, 3.90 Å: 2YVZ	2YVX	Hattori et al. (2007)
*MgtE Mg²⁺ Transporter: Thermus thermophilus* (expressed in E. coli), 2.9 Å**	2ZY9	Hattori et al. (2009)
*SLAC1 anion channel, TehA homolog (wild-type): Haemophilus influenzae* (expressed in E. coli), 1.2 Å** F262A mutant, 1.15 Å: 3M73 F262L mutant, 1.65 Å: 3M74 F262V mutant, 1.60 Å: 3M75 G15D mutant, 1.50 Å: 3M76	3M71	Chen et al. (2010)
Channels: Protein-Conducting
*SecYEβ protein-conducting channel: Methanococcus jannaschii, 3.5 Å* Coördinates of native complex: 1RHZ. Coördinates of double-mutant complex (K422R,V423T) 1RH5 (3.2 Å resolution).	1RHZ	van den Berg et al. (2004)
*SecYEβ protein-conducting channel with full-plug (TM2a) deletion: Methanococcus jannaschii, 3.6 Å* Coördinates of mutant with half-plug deletion 2YXQ (3.5 Å resolution).	2YXR	Li et al. (2007)
*SecYEβ "primed" protein-conducting channel: Pyrococcus furiosus* (expressed in E. coli), 3.1 Å**	3MP7	Egea and Stroud (2010)
*SecYEG protein-conducting channel in complex with SecA: Thermotoga maritima* (expressed in E. coli), 4.5 Å**	3DIN	Zimmer et al. (2008)
*SecYE protein-conducting channel in complex with a Fab fragment: Thermus thermophilus* (expressed in E. coli), 3.20 Å** SecYE alone 2ZQP (6.0 Å resolution).	2ZJS	Tsukazaki et al. (2008)
Channels: Aquaporins and Glyceroporins
AQP0 aquaporin water channel: Bovine lens, 2.24 Å	1YMG	Harries et al. (2004)
AQP0 aquaporin water channel: Ovine lens, electron diffraction, 3.0 Å (plane) by 3.5 Å (normal) AQP0 reconstituted with dimyristoylphosphatidylcholine and organized as a membrane junction.	1SOR	Gonen et al. (2004)
AQP0 aquaporin lens junction: Ovine lens, electron diffraction, 1.9 Å Non-junctional form, 2.4 Å: 2B6P	2B6O	Gonen et al. (2005)
AQP0 aquaporin lens junction: Ovine lens, electron diffraction, 2.5 Å AQP0 reconstituted with E. coli polar lipids and organized as a membrane junction	3M9I	Hite et al. (2010)
AQP1 aquaporin water channel: Human red blood cell, electron diffraction, 3.8 Å (in membrane plane)	1FQY	Murata et al. (2000)
AQP1 aquaporin water channel: Human red blood cell, in vitreous ice by electron diffraction, 3.7 Å	1IH5	Ren et al. (2001)
AQP1 aquaporin water channel: Bovine red blood cell, X-ray diffraction, 2.2 Å	1J4N	Sui et al. (2001)
AQP4 aquaporin water channel: rat glial cells (expressed in insect cells), electron diffraction, 3.2 Å	2D57	Hiroaki et al. (2005)
AQP4 aquaporin water channel: rat glial cells (expressed in insect cells), electron diffraction, 2.8 Å S180D mutant. Structure reveals five lipids associated with AQP4.	2ZZ9	Tani et al. (2009)
*AQP4 aquaporin water channel: Human (expressed in Pichia pastoris), 1.8 Å*	3GD8	Ho et al. (2009)
*AQP5 aquaporin water channel (HsAQP5): human (expressed in Pichia pastoris), 2.0 Å*	3D9S	Horsefield et al. (2008)
*AqpM aquaporin water channel: Methanothermobacter marburgensis* (expressed in E. coli), 1.68 Å** Initial structure, 2.3 Å: 2EVU	2F2B	Lee et al. (2005)
*AqpZ aquaporin water channel: Escherichia coli, 2.5 Å*	1RC2	Savage et al. (2003)
*AqpZ aquaporin showing two conformations of Arg-189: Escherichia coli, 3.2 Å*	2ABM	Jiang et al. (2006)
*AqpZ aquaporin (C9S/C20S), T183C mutant without Hg: Escherichia coli, 2.30 Å* T183C with Hg, 2.20 Å: 2O9E. L170C without Hg, 2.55 Å: 2O9F. L170C with Hg, 1.90 Å: 2O9G.	2O9D	Savage & Stroud (2007)
*AqpZ aquaporin mutant F43W : Escherichia coli, 2.40 Å* H174G/T183F mutant, 2.50 Å: 3NKA. F43W/H174G/T183F mutant, 3.10 Å: 3NKC.	3NK5	Savage et al. (2010)
*SoPIP2;1 plant aquaporin (closed conformation): Spinacia oleracea* (expressed in Pichia pastoris), 2.1 Å** Open conformation, 3.9 Å: 2B5F	1Z98	Törnroth-Horsefield et al. (2006)
*GlpF glycerol facilitator channel: Escherichia coli, 2.2 Å*	1FX8	Fu et al. (2000)
*GlpF glycerol facilitator channel, W84F/F200T-mutant: Escherichia coli, 2.1 Å* GlpF with non-transported xylose replacing glycerol: (GlpF - G)_A, 2.7 Å: 1LDI GlpF with non-transported xylose replacing glycerol: (GlpF - G)_B, 2.8 Å: 1LDA	1LDF	Tajkhorshid et al. (2002)
*PfAQP aquaglyceroporin: Plasmodium falciparum, 2.05 Å* Transports water and glycerol equally well.	3C02	Newby et al. (2008)
*Aqy1 yeast aquaporin (pH 3.5): Pischia pastoris, 1.15 Å* pH 8.0, 1.40 Å: 2W1P	2W2E	Fischer et al. (2009)
Channels : Formate Nitrate Transporter (FNT) Family
*FocA, pentameric aquaporin-like formate transporter: Escherichia coli, 2.20 Å* 3KCU structure is for P2₁2₁2₁ space group. P3₂ space group: 3KCV, 3.2 Å	3KCU	Wang et al. (2009)
*FocA formate transporter without formate: Vibrio cholerae* (expressed in E. coli), 2.10 Å** FocA with bound formate: 3KLZ, 2.50 Å	3KLY	Waight et al. (2010)
*FocA formate transporter at pH 4.0: Salmonela typhimurium* (expressed in E. coli), 2.80 Å** Three different conformations are observed in the asymmetric unit: Open, Intermediate, & closed.	3Q7K	Lü et al. (2011)
Channels: Urea Transporters
*Urea transporter: Desulfovibrio vulgaris* (expressed in E. coli), 2.30 Å** Structure with bound dimethyl urea: 3K3G, 2.40 Å	3K3F	Levin et al. (2009)
Channels: Gap Junctions
Connexin 26 (Cx26; GJB2) gap junction: Human (expressed in Sf9 cells), 3.5 Å	2ZW3	Maeda et al. (2009)
Channels: Amt/Rh proteins
*AmtB ammonia channel (mutant): Escherichia coli, 1.40 Å* 1U7G is Protein + ammonia. Apoprotein, 2.0 Å: 1U77 Protein + methylammonia, 1.85 Å: 1U7C	1U7G	Khademi et al. (2004)
*AmtB ammonia channel (wild-type): Escherichia coli, 1.8 Å (P6₃ crystal form)* R3 crystal form: 1XQE, 2.1 Å resolution	1XQF	Zheng et al. (2004)
*AmtB ammonia channel (wild-type): Escherichia coli, 2.1 Å* Wild-type in the presence of ammonium with imidazole: 2NOP, 2.0 Å H168E mutant in the presence of ammonium: 2NOW, 2.2 Å H168A mutant in the presence of ammonium with imidazole: 2NPC, 2.1 Å H168F mutant in the presence of ammonium with imidazole: 2NPD, 2.1 Å H318A mutant in the absence of ammonium: 2NPE, 2.1 Å H318F mutant in the presence of ammonium: 2NPG, 2.0 Å H318F mutant in the presence of ammonium with imidazole: 2NPJ, 2.0 Å H168A/H318A mutant in the presence of ammonium with imidazole: 2NPK, 2.0 Å	2NMR	Javelle et al. (2006)
*AmtB ammonia channel in complex with GlnK: Escherichia coli, 2.5 Å*	2NUU	Conroy et al. (2007)
*AmtB ammonia channel in complex with inhibitory GlnK: Escherichia coli, 1.96 Å*	2NS1	Gruswitz et al. (2007)
*Amt-1 ammonium channel: Archaeoglobus fulgidus* (expressed in E. coli), 1.72 Å** Native protein: 2B2F. Protein + 20 mM Ammonium Sulfate: 2B2H Protein + 80 mM Ammonium Sulfate: 2B2I Protein+xenon: 2B2J	2B2F	Andrade et al. (2005)
*Rh protein, possible ammonia or CO₂ channel: Nitrosomonas europaea* (expressed in Methylococcus capsulatus), 1.85 Å** CO₂ pressurized protein, 1.85 Å: 3B9Z	3B9Y	Li et al. (2007)
*Rh protein, possible ammonia or CO₂ channel: Nitrosomonas europaea* (expressed in E. coli), 1.30 Å**	3B9W	Lupo et al. (2007)
*Human Rh C glycoprotein ammonia transporter: Homo sapiens* (expressed in HEK293s cells), 2.10 Å**	3HD6	Gruswitz et al. (2010)
Intramembrane Proteases ( NSMB News & Views on three GlpG Structures)
*GlpG rhomboid-family intramembrane protease: Eschericia coli, 2.1 Å* P3₂ space group. One molecule in asymmetric unit.	2IC8	Wang et al. (2006)
*GlpG rhomboid-family intramembrane protease: Eschericia coli, 1.90 Å* W136A mutant, 1.70 Å: 3B44	3B45	Wang et al. (2007)
*GlpG rhomboid-family intramembrane protease: Eschericia coli, 2.5 Å* Shows GlpG in a more open conformation.	2O7L	Wang & Ha (2007)
*GlpG rhomboid-family intramembrane protease: Eschericia coli, 2.6 Å* P3₁ space group. Two anti-parallel molecules in asymmetric unit.	2NRF	Wu et al. (2006)
*GlpG rhomboid-family intramembrane protease: Eschericia coli, 2.3 Å* P2₁ space group. Two anti-parallel molecules in asymmetric unit.	2IRV	Ben-Shem et al. (2007)
*GlpG rhomboid-family intramembrane protease: Eschericia coli, 1.65 Å* Acyl GlpG: GlpG with covalently bound isocoumarin inhibitor, 2.09 Å: 2XOW	2XOV	Vinothkumar et al. (2010)
*GlpG rhomboid-family intramembrane protease with lipids: Eschericia coli, 1.70 Å* S201T active-site mutant in orthorhombic crystal form. S201T active-site mutant in trigonal crystal form, 1.85 Å: 2XTU	2XTV	Vinothkumar (2011)
*GlpG rhomboid-family intramembrane peptidase: Haemophilus influenzae* (Expressed in E. coli), 2.2 Å** Shows three bound lipid molecules. Monoclinic C2 space group.	2NR9	Lemieux et al. (2007)
*GlpG rhomboid-family intramembrane peptidase: Haemophilus influenzae* (Expressed in E. coli), 2.84 Å** Reveals disorder in loops 4 and 5 and helix 5.	3ODJ	Brooks et al. (2011)
*Site-2 Protease (S2P). Intramembrane Metalloprotease: Methanocaldococcus jannaschii, 3.3 Å* Structure is of the transmembrane core only.	3B4R	Feng et al. (2007)
*Signal Peptide Peptidase (SppA), native protein: Escherichia coli, 2.55 Å* SeMet protein, 2.76 Å: 3BEZ. Long thought to be a transmembrane protein, the structure reveals a peripheral homotetramer that likely is buried in the membrane interface. Each monomer has a putative N-terminal transmembrane helix for anchoring to the membrane. This anchor was removed for crystallization. Also listed under Monotopic Membrane Proteins.	3BF0	Kim et al. (2008)
Membrane-Bound Metalloproteases
apo-FtsH ATP-dependent metalloprotease: Thermotoga maritima (expressed in E. coli), 2.60 Å This is a homo-hexameric AAA+ protease. Each monomer is anchored to the cytoplasmic membrane by two transmembrane segments, which are missing in the structure. The protease can degrade both soluble and membrane proteins.	3KDS	Bieniossek et al. (2009)
H⁺/Cl^- Exchange Transporters
*H⁺/Cl^- Exchange Transporter: Salmonella typhimurium* (Expressed in E. coli), 3.0 Å** Formerly ClC Chloride Channel. Eschericia coli protein, 3.5 Å: 1KPK	1KPL	Dutzler et al. (2002)
*H⁺/Cl^- Exchange Transporter: Escherichia coli, 2.51 Å* Formerly ClC Chloride Channel. Structure reveals gating by a glutamate residue E148A mutant, 3.00 Å: 1OTT. E148Q mutant, 3.30 Å: 1OTU.	1OTS	Dutzler et al. (2003)
*H⁺/Cl^- Exchange Transporter without bound ions: Escherichia coli, 3.20 Å* E148Q mutant without bound ions, 3.1 Å: 2EXY. S107A/E148Q/Y445A mutant with bound Br^-, 3.54 Å: 2EZ0.	2EXW	Lobet & Dutzler (2006)
*Monomeric H⁺/Cl^- Exchange Transporter: Escherichia coli, 3.10 Å* ClC transporter was engineered to place tryptophan residues (I201W; I422W) at the momomer-monomer interface to prevent dimerization.	3NMO	Robertson et al. (2010)
*H⁺/Cl^- Eukaryotic Exchange Transporter: Cyanidioschyzon merolae* (Expressed in Trichoplusia ni), 3.50 Å**	3ORG	Feng et al. (2010)
*H⁺/Cl^- Eukaryotic Exchange Transporter: Synechocystis* sp. pcc 6803 (Expressed in E. coli), 3.20 Å** In the presence of Br⁻, 3.60 Å: 3Q17	3ND0	Jayaram et al. (2011)
Bacterial Mercury Detoxification Proteins
*MerF Hg(II) transporter: Morganella morganii/* (Expressed in E. coli), NMR structure** Structure of truncated protein (AAs 13-72) determined in aligned bicelles.	2H3O	De Angelis et al. (2006)
*MerF Hg(II) transporter: Morganella morganii* (Expressed in E. coli), NMR structure** Structure of truncated protein (AAs 13-72) determined in SDS micelles.	1WAZ	Howell et al. (2005)
Multi-Drug Efflux Transporters
*AcrB bacterial multi-drug efflux transporter: Escherichia coli, 3.5 Å*	1IWG	Murakami et al. (2002)
*AcrB bacterial multi-drug efflux transporter: Escherichia coli, 3.7 Å* With substrates: rhodamine 6G, 3.63 Å: 1OY8. ethidium, 3.80 Å: 1OY9. dequalinium, 3.80 Å: 1OYD. ciprofloxacin, 3.48 Å: 1OYE.	1OY6	Yu et al. (2003)
*AcrB bacterial multi-drug efflux transporter, apo protein, N109A mutant: Escherichia coli, 3.23 Å* With substrates: ciprofloxacin, 3.11 Å: 1T9U. rhodamine 6G, 3.80 Å: 1T9V. nafcillin, 3.23 Å: 1T9W. ethidium, 3.08 Å: 1T9X. Phe-Arg-β-naphthylamide, 3.64 Å: 1T9Y.	1T9T	Yu et al. (2005)
*AcrB bacterial multi-drug efflux transporter, D407A mutant: Escherichia coli, 3.56 Å* D408A, 3.65 Å: 2HQD. K940A, 3.38 Å: 2HQF. T978A, 3.38 Å: 2HQG.	2HQC	Su et al. (2006)
*AcrB bacterial multi-drug efflux transporter: Escherichia coli, 2.9 Å* Two crystal forms. C2: 2GIF. P1: 2HRT, 3.0 Å. Together, the two forms suggest a pump mechanism.	2GIF	Seeger et al. (2006)
*AcrB bacterial multi-drug efflux transporter without ligands: Escherichia coli, 2.8 Å* With minocycline, 3.1 Å: 2DRD. With doxorubicin, 3.3 Å: 2DR6	2DHH	Murakami et al. (2006)
*AcrB bacterial multi-drug efflux transporter with YajC subunit: Escherichia coli, 3.5 Å*	2RDD	Törnroth-Horsefield et al. (2007)
*AcrB bacterial multi-drug efflux transporter in complex with bile acid: Escherichia coli, 3.85 Å*	2W1B	Drew et al. (2008)
*MexB bacterial multi-drug efflux transporter: Pseudomonas aeruginosa* (expressed in E. coli), 3.0 Å**	2V50	Sennhauser et al. (2009)
*CusA metal-ion efflux pump: Escherichia coli, 3.52 Å*	3K07	Long et al. (2010)
*EmrE bacterial multi-drug efflux transporter with bound TPP substrate: Escherichia coli, 3.8 Å* 3B5D is C2 crystal form. P2₁ form with TPP, 4.5 Å: 3B62 3B5D and 3B62 expressed in cell-free system. Ligand-free structure expressed in vivo, 4.5 Å: 3B61	3B5D	Chen et al. (2007)
*NorM Multidrug and Toxin Compound Extrusion (MATE) transporter (apo form): Vibrio cholerae* (Expressed in E. coli), 3.65 Å** With bound Rb⁺, 4.20 Å: 3MKU	3MKT	He et al. (2010)
Membrane-Associated Proteins in Eicosanoid and Glutathione Metabolism (MAPEG)
*Microsomal Glutathione Transferase 1: Rattus norvegicus, 3.2 Å* (Electron Diffraction)	2H8A	Holm et al. (2006)
*Microsomal Prostaglandin E Synthase 1: Human (expressed in E. coli), 3.5 Å* (Electron Diffraction) In complex with glutathione.	3DWW	Jegerschöld et al. (2008)
*5-Lipoxygenase-Activating Protein (FLAP) with Bound MK-591 Inhibitor: Human (expressed in E. coli), 4.0 Å* FLAP with iodinated MK-591 analog: 2Q7R.	2Q7M	Ferguson et al. (2007)
*Leukotriene LTC₄ Synthase in complex with glutathione: Human* (expressed in Shizosaccharomyces pombe), 3.3 Å**	2PNO	Ago et al. (2007)
*Leukotriene LTC₄ Synthase in complex with glutathione: Human* (expressed in Pichia pastoris.), 2.15 Å** apo form: 2UUI, 2.00 Å.	2UUH	Molina et al. (2007)
Major Facilitator Superfamily (MFS) Transporters
*LacY Lactose Permease Transporter (C154G mutant): Escherichia coli, 3.6 Å* 1PV7 is with bound high-affinity lactose homolog, TDG. See 1PV6 for structure without TDG (3.5 Å).	1PV7	Abramson et al. (2003)
*LacY Lactose Permease (C154G mutant) without substrate at 2 pH values: Escherichia coli, 2.95 Å* 2CFQ structure determined at pH 6.5. 2CFP structure determined at pH 5.6 (3.30 Å).	2CFQ	Mirza et al. (2006)
*LacY Lactose Permease (wild-type) with TDG: Escherichia coli, 3.6 Å*	2V8N	Guan et al. (2007)
*FucP Fucose Transporter in outward-facing conformation: Escherichia coli, 3.1 Å* N162A mutant, 3.2 Å: 3O7P	3O7Q	Dang et al. (2010)
*GlpT Glycerol-3-Phosphate Transporter: Escherichia coli, 3.3 Å*	1PW4	Huang et al. (2003)
*EmrD Multidrug Transporter: Escherichia coli, 3.5 Å*	2GFP	Yin et al. (2006)
*PepT_So Oligopeptide-proton symporter: Shewanella oneidensis* (expressed in E. coli), 3.6 Å**	2XUT	Newstead et al. (2011)
Solute Sodium Symporter (SSS) Family
*vSGLT Sodium Galactose Transporter: Vibrio parahaemolyticus* (expressed in E. coli), 2.70 Å** Galactose-bound inward-occuluded conformation	3DH4	Faham et al. (2008)
*vSGLT Sodium Galactose Transporter, K294A mutant: Vibrio parahaemolyticus* (expressed in E. coli), 2.70 Å** inward-open conformation	2XQ2	Watanabe et al. (2010)
Nucleobase-Cation-Symport-1 (NCS1) Family
*Mhp1 Benzyl-hydantoin transporter (without substrate); outward-facing conformation: Microbacterium liquefaciens* (expressed in E. coli), 2.85 Å** With hydantion substrate; closed conformation, 4.0 Å: 2JLO.	2JLN	Weyand et al. (2008)
*Mhp1 Benzyl-hydantoin transporter; inward-facing conformation: Microbacterium liquefaciens* (expressed in E. coli), 3.8 Å**	2X79	Shimamura et al. (2010)
Betaine/Choline/Carnitine Transporter (BCCT) Family
*BetP glycine betaine transporter: Corynebacterium glutamicum* (expressed in E. coli), 3.35 Å** A Na⁺-coupled symporter in an intermediate state. Formerly PDB 2W8A.	2WIT	Ressl et al. (2009)
*CaiT carnitine transporter: Escherichia coli, 3.15 Å* This is a precursor/product antiporter that catalyzes the exchange of L-carnitine wtih γ-butyrobetaine. The protein is a homotrimer with each monomer containing 12 transmembrane helices.	3HFX	Tang et al. (2010)
*CaiT carnitine transporter: Escherichia coli, 3.50 Å* Fully-open inward-facing conformation.	2WSX	Schulze et al. (2010)
*CaiT carnitine transporter: Proteus mirabilis, 2.3 Å* Fully-open inward-facing conformation.	2WSW	Schulze et al. (2010)
Amino Acid/Polyamine/Organocation (APC) Superfamily
*AdiC Arginine:Agmatine Antiporter: Escherichia coli, 3.61 Å* 3LRB is a re-refinement of the original 3H5B structure, which contained a register shift of 3-4 amino acids relative to 3NCY and 3GIA (below).	3LRB	Gao et al. (2009)
*AdiC Arginine:Agmatine Antiporter (N22A, L123W mutant) with bound Arginine: Escherichia coli, 3.0 Å* Outward-facing occluded state	3L1L	Gao et al. (2010)
*AdiC Arginine:Agmatine Antiporter (N101A mutant) with bound Arginine: Escherichia coli, 3.0 Å* Reveals AdiC in the open-to-out conformation.	3OB6	Kowalczyk et al. (2011)
*AdiC Arginine:Agmatine Antiporter (with Fab fragment): Salmonella enterica* (expressed in E. coli), 3.2 Å** PDB ID was originally 3HQK, which has been superseded by 3NCY.	3NCY	Fang et al. (2009)
*apo ApcT Na⁺-independent Amino Acid Transporter: Methanocaldococcus jannaschii* (expressed in E. coli), 2.35 Å** ApcT-7F11 Fab complex, 2.50 Å: 3GI9 ApcT-K158A/7F11 Fab complex, 2.60 Å: 3GI8	3GIA	Shaffer et al. (2009)
Amino Acid Secondary Transporters
*LeuT_Aa Leucine transporter: Aquifex aeolicus* (expressed in E. coli), 1.65 Å**	2A65	Yamashita et al. (2005)
*LeuT Leucine transporter with bound inhibitors: Aquifex aeolicus* (expressed in E. coli), 1.85 Å** Alanine-Sodium-Clomipramine Leucine-Sodium-Clomipramine, 2Q6H Leucine-Sodium-Imipramine, 2Q72 Leucine-Sodium-Desipramine, 2QB4	2QEI	Singh et al. (2007)
*LeuT Leucine transporter with bound Na⁺ and tryptophan: Aquifex aeolicus* (expressed in E. coli), 2.00 Å**. Shows the transporter in an open-to-out conformation. w. bound glycine, 2.15 Å: 3F4J w. bound alanine, 1.90 Å: 3F48 w. bound leucine (30mM), 1.80 Å: 3F3E w. bound methionine, 1.90 Å: 3F3D w. bound selenomethionine, 1.95 Å: 3F4I w. bound 4-fluorophenylalanine, 2.10 Å: 3F3C	3F3A	Singh et al. (2009)
*LeuT Leucine Transporter with Bound Desipramine: Aquifex aeolicus* (expressed in E. coli), 2.9 Å**	2QJU	Zhou et al. (2007)
*Wild-type LeuT transporter with bound octylglucopyranoside (OG): Aquifex aeolicus* (expressed in E. coli), 2.0 Å** E290S mutant with bound OG, 2.8 Å: 3GJC	3GJD	Quick et al. (2009)
*Mutant LeuT transporter with Nitroxide Spin Label (F177R1): Aquifex aeolicus* (expressed in E. coli), 2.25 Å** I204R1 mutant, 2.25 Å: 3MPQ	3MPN	Kroncke et al. (2010)
*Glutamate Transporter Homologue (Glt_Ph): Pyrococcus horikoshii* (expressed in E. coli), 3.50 Å** Outward-facing state	1XFH	Yernool et al. (2004)
*Glutamate Transporter Homologue (Glt_Ph): Pyrococcus horikoshii* (expressed in E. coli), 3.51 Å** Inward-facing state	3KBC	Reyes et al. (2009)
*Aspartate Transporter Li⁺-Bound State(Glt_Ph): Pyrococcus horikoshii* (expressed in E. coli), 2.96 Å** TBOA-bound, 3.20 Å: 2NWW Sodium-bound, 3.29 Å: 2NWX	2NWL	Boudker et al. (2007)
Cation Diffusion Facilitator (CDF) Family
*YiiP Zinc Transporter: Escherichia coli, 3.8 Å* Renamed FieF iron & zinc transporter (see Grass et al. Arch. Microbiol. 183:9-18, 2005)	2QFI	Lu & Fu (2007)
*YiiP Zinc Transporter: Escherichia coli, 2.9 Å* Renamed FieF iron & zinc transporter (see Grass et al. Arch. Microbiol. 183:9-18, 2005)	3H90	Lu et al. (2009)
Antiporters
*NhaA Na⁺/H⁺ antiporter: Escherichia coli, 3.45 Å*	1ZCD	Hunte et al. (2005)
*NhaA Na⁺/H⁺ antiporter: Escherichia coli, by electron crystallography* Difference maps show structural changes with changes in pH.	3FI1	Appel et al. (2009)
Mitochondrial ADP/ATP Carrier: Bovine heart mitochondria, 2.2 Å Monomeric, in complex with carboxyatractyloside inhibitor.	1OKC	Pebay-Peyroula et al. (2003)
Mitochondrial ADP/ATP Carrier: Bovine heart mitochondria, 2.8 Å Biological dimer with endogenous cardiolipins.	2C3E	Nury et al. (2005)
Energy-Coupling Factor (ECF) Transporters
*RibU, S Component of the Riboflavin Transporter: Staphylococcus aureus* (Expressed in E. coli), 3.6 Å**	3P5N	Zhang et al. (2010)
ATP Binding Cassette (ABC) Transporters
*BtuCD Vitamin B₁₂ Transporter: Escherichia coli, 3.2 Å*	1L7V	Locher et al. (2002)
*BtuCD-F Complex; BtuCD B₁₂ Transporter + BtuF binding protein: Escherichia coli, 2.6 Å*	2QI9	Hvorup et al. (2007)
*Sav1866 Multidrug Transporter: Staphylococcus aureus, 3.0 Å*	2HYD	Dawson and Locher (2006)
*Molybdate Transporter ModB₂C₂ Complexed with ModA: Archaeoglobus fulgidus, 3.1 Å* ModA with bound MoO₄, 1.60 Å 2ONR ModA with bound WO₄, 1.55 Å 2ONS	2ONK	Hollenstein et al. (2007)
*ModBC Molybdate ABC Transporter in a trans-inhibited state: Methanosarcina acetivorans, 3.0 Å*	3D31	Gerber et al. (2008)
*HI1470/1 Putative Metal-Chelate-type ABC Transporter: Haemophilus influenzae, 2.4 Å* First structure showing an inward-facing conformation of an ABC transporter	2NQ2	Pinkett et al. (2007)
*MsbA Lipid "flippase" with bound AMPPNP: Salmonella typhimurium* (expressed in E. coli), 3.7 Å** MsbA with bound AMPPNP used for initial model: 3B5Y, 4.5 Å ADP + Vanadate-bound conformation: 3B5Z, 4.2 Å Open apo-conformation (E. coli): 3B5W, 5.3 Å Closed apo-conformation (Vibrio cholerae expressed in E. coli): 3B5X, 5.5 Å	3B60	Ward et al. (2007)
*P-Glycoprotein: Mus musculus* (mouse) (expressed in Pichia pastoris), 3.8 Å** With bound QZ59-RRR: 3G60, 4.40 Å With bound QZ59-SSS: 3G61, 4.35 Å	3G5U	Aller et al. (2009)
*MalFGK₂-MBP Maltose uptake transporter complex: Escherichia coli, 2.8 Å* Complex includes maltose-binding protein (MBP), maltose, and ATP	2R6G	Oldham et al. (2007)
*MalFGK₂ uptake transporter: Escherichia coli, 4.5 Å* Helix TM1 deleted. Shows transporter in the inward conformation in the resting state.	3FH6	Khare et al. (2009)
*MetNI Methionine uptake transporter complex: Escherichia coli, 3.7 Å* MetN-C2 domain 3DHX, 2.1 Å	3DHW	Kadaba et al. (2008)
*FbpC ferric iron-uptake transporter nucleotide-binding domain: Neisseria gonorrhoeae, 1.9 Å* A domain-swapped neucleotide-binding domain dimer	3FVQ	Newstead et al. (2009)
Superfamily of K⁺ Transporters (SKT proteins)
*TrkH potassium ion transporter: Vibrio parahaemolyticus* (Expressed in E. coli), 3.51 Å** Lacking a Na⁺/K⁺-ATPase, non-animal cells require two different systems for K⁺ uptake, one of which is the SKT proteins.	3PJZ	Cao et al. (2011)
P-type ATPase
Calcium ATPase: Rabbit sarcoplasmic reticulum; E1 state with bound calcium, 2.4 Å These ATPases are referred to as SERCA pumps; SERCA: Sarco(Endo)plasmic Reticulum CAlcium	1SU4	Toyoshima et al. (2000)
Calcium ATPase: Rabbit sarcoplasmic reticulum (E1 state with bound calcium, magnesium, and an ATP analog), 2.9 Å	1VFP	Toyoshima & Mizutani (2004)
Calcium ATPase: Rabbit sarcoplasmic reticulum (E2 state without bound calcium), 3.1 Å	1IWO	Toyoshima & Nomura (2002)
Calcium ATPase: Rabbit sarcoplasmic reticulum (E2 state calcium-free with bound magnesium fluoride), 2.3 Å E1 state with bound AlF_x and ADP, 2.40 Å: 2ZDB (supersedes 1WPE, which was superseded by 2Z9R)	1WPG	Toyoshima et al. (2004)
Calcium ATPase: Rabbit sarcoplamic reticulum (E1 state with bound calcium and AMPPC), 2.6 Å E1 state with bound calcium and ADP:AlF₄^–, 2.9 Å: 1T5T	1T5S	Sørensen et al. (2004)
Calcium ATPase: Rabbit sarcoplasmic reticulum (E2 state with bound AlF₄^– calcium-free), 3.0 Å	1XP5	Olesen et al. (2004)
Calcium ATPase: Rabbit sarcoplasmic reticulum (Ca²⁺-free, with bound BHQ and thapsigargin), 3.0 Å	2AGV	Obara et al. (2005)
Calcium ATPase: Rabbit sarcoplasmic reticulum (with bound synthesized derivative of thapsigargin), 3.30 Å	2BY4	Søhoel et al. (2006)
Calcium ATPase: Rabbit sarcoplamic reticulum (Ca²-free E2 state with thapsigargin and AMPPCP), 3.10 Å With partially occupied AMPPCP site, 2.80 Å: 2C8K With thapsigargin, 3.10 Å: 2C8L In the Ca²⁺ E1 state solved in a P1 crystal form, 3.00 Å: 2C9M	2C88	Jensen et al. (2006)
Calcium ATPase: Rabbit sarcoplamic reticulum (Calcium-free with bound AlF₄^– and cyclopiazonic acid (CPA)), 2.65 Å Calcium-free with bound CPA and ADP, 3.4 Å: 2OA0	2O9J	Moncoq et al. (2007)
Calcium ATPase: Rabbit sarcoplamic reticulum (P21 crystal form with bound thapsigargin, 3.10) Å With bound CPA, 3.4 Å: 3EAS With bound CPA and thapsigargin, 2.90 Å: 3EAT With bound CPA in the presence of curcumin, 2.80 Å: 3EAU	3EAR	Takahashi et al. (2007)
Calcium ATPase: Rabbit sarcoplamic reticulum (Ca₂E1~P (Ca₂E1~P.AMPPN)), 2.8 Å E2P (E2-BeF₃^–), 2.65 Å: 3B9B E2-P* (E2-AlF₄^–), 3.0 Å: 3B9R	3BA6	Olesen et al. (2007)
Na,K-ATPase: Pig Kidney, 3.5 Å	3B8E	Morth et al. (2007)
*Na,K-ATPase: Shark (Squalus acanthias), 2.4 Å* Includes α and β subunits plus FXYD regulatory protein. Reveals coordination of K⁺ in the transmembrane binding site.	2ZXE	Shinoda et al. (2009)
*Na,K-ATPase Regulatory Protein FXYD1: Human (expressed in E. coli), NMR Structure*	2JO1	Teriete et al. (2007)
Phospholamban homopentamer: Human sarcoplasmic reticulum, NMR structure See also 1FJK and 1FJP.	1ZLL	Oxenoid and Chou (2005)
*Plasma Membrane H⁺-ATPase: Arabidopsis thaliana, 3.6 Å*	3B8C	Pedersen et al. (2007)
V-type ATPase
*Rotor of V-type Na⁺-ATPase: Enterococcus hirae, 2.1 Å*	2BL2	Murata et al. (2005)
*V₁-ATPase Complex (V-ATPase soluble domain) with bound nucleotide: Thermus thermophilus, 4.51 Å* Without nucleotide, 4.80 Å: 3A5D	3A5C	Numoto et al. (2009)
*A₃B₃ complex of V₁-ATPase: Thermus thermophilus* (expressed in E. coli), 2.8 Å**	3GQB	Maher et al. (2009)
F-type ATPase
*F₁-ATPase from bovine heart mitochondria: Bos taurus, 2.8 Å*	1BMF	Abrahams et al. (1994)
*F₁-ATPase complexed with antibiotic inhibitor aurovertin B: Bos taurus, 3.10 Å*	1COW	van Raaij et al. (1996)
*F₁-ATPase complexed with peptide antibiotic efrapeptin: Bos taurus, 3.10 Å*	1EFR	Abrahams et al. (1996)
*F₁-ATPase complexed with azide: Bos taurus, 1.95 Å*	2CK3	Bowler et al. (2006)
*F₁-ATPase, Ground State Structure: Bos taurus, 1.90 Å*	2JDI	Bowler et al. (2007)
*ATP Synthase Extrinsic Region: Bos taurus, 3.2 Å*	2WSS	Rees et al. (2009)
*ATP synthase (F₁c₁₀): S. cerevisiae, 3.9 Å* NOTE: X-ray structure is a C-alpha model derived from composite of 1BMF, 1A91, & 1AQT	1QO1	Stock et al. (1999)
*F₁ ATPase: S. cerevisiae, 2.80 Å*	2HLD	Kabaleeswaran et al. (2006)
*Rotor (c₁₁) of Na⁺-dependent F-ATP Synthase: Ilyobacter tartaricus, 2.4 Å*	1YCE	Meier et al. (2005)
*Rotor (c₁₁) of Na⁺-dependent F-ATP Synthase with complete ion-coördination structure: Ilyobacter tartaricus, 2.35 Å*	2WGM	Meier et al. (2009)
*Rotor (c₁₄) of H⁺-dependent F-ATP Synthase of spinach chloroplasts: Spinacia oleracea, 3.80 Å*	2W5J	Vollmar et al. (2009)
*Rotor (c₁₅) of H⁺-dependent F-ATP Synthase of an alkaliphilic cyanobacterium: Spirulina platensis, 2.1 Å*	2WIE	Pogoryelov et al. (2009)
*Rotor (c₁₃) of H⁺-dependent F-ATP Synthase: Bacillus pseudofirmus* OF4, 2.5 Å**	2X2V	Preiss et al. (2010)
*Peripheral stalk of H⁺-dependent F-ATP Synthase: Thermus thermophilus* (expressed in E. coli), 3.10 Å**	3K5B	Lee et al. (2010)
Phosphotransferases
*Diacylglycerol kinase (DAGK): Escherichia coli, NMR structure (DPC micelles)* Domain-swapped homotrimer	2KDC	van Horn et al.. (2009)
Hydrolases
Estrone Sulfatase: Human placenta, 2.6 Å	1P49	Hernandez-Guzman et al. (2003)
Oxygenases
*Particulate methane monooxgenase (pMMO): Methylococcus capsulatus, 2.8 Å*	1YEW	Lieberman & Rosenzweig (2005)
*Particulate methane monooxgenase (pMMO): Methylosinus trichosporium* OB3b, 3.90 Å**	3CHX	Hakemian et al. (2008)
Oxidoreductases
*Sulfide:quinone oxidoreductase in complex with decylubiquinone: Aquifex aeolicus, 2.0 Å* "as-purified" protein, 2.30 Å: 3HYV in complex with aurachin C, 2.9 Å: 3HYX This is a monotopic membrane protein thought to be buried about 12 Å in the bilayer interface. Also listed under Monotopic Membrane Proteins.	3HYW	Marcia et al. (2009)
*Electron Transfer Flavoprotein-ubiquinone oxidoreductase (ETF-QO) with bound UQ: Sus scrofa, 2.5 Å* UQ-free structure, 2.6 Å: 2GMJ. This is a monotopic membrane protein. See main entry under Monotopic Membrane Proteins.	2GMH	Zhang et al. (2006)
*Glycerol-3-phosphate dehydrogenase (GlpD, native): Escherichia coli, 1.75 Å* This is a monotopic membrane protein. See main entry under Monotopic Membrane Proteins	2QCU	Yeh et al. (2008)
*NarGHI Nitrate Reductase A: Escherichia coli, 1.9 Å*	1Q16	Bertero et al. (2003)
*NarGHI Nitrate Reductase A catalytic domain NarG with FS0 cluster: Escherichia coli, 2.2 Å*	1SIW	Rothery et al. (2004)
*NarGHI Nitrate Reductase with pentachlorophenol (PCP): Escherichia coli, 2.0 Å* K86A mutant, 1.90 Å : 1Y5I. K86A w. PCP, 2.50 Å : 1Y5N. H66Y mutant, 2.50 Å : 1Y5L.	1Y4Z	Bertero et al. (2005)
*NrfH Cytochrome C Quinol Dehydrogenase: Desulfovibrio vulgaris, 2.3 Å* In complex with NrfA cytochrome c nitrite reductase.	2J7A	Rodrigues et al. (2006)
*DsbB-DsbA Periplasmic Oxidase Complex: E. coli, 3.7 Å* DsbB is a four-helix bundle membrane protein that works with the periplasmic DsbA oxidase to introduce disulfide bonds into periplasmic proteins.	2HI7	Inaba et al. (2006)
*DsbB-Fab complex: Eschericia coli, 3.4 Å* Shows the principal Cys104-Cys130 disulfide Updated DsbB-DsbA complex: 3.7 Å 2ZUP	2ZUQ	Inaba et al. (2009)
*wtDsbB-DsbA(Cys133A)-Q8 Complex: E. coli, 3.7 Å*	3E9J	Malojcic et al. (2008)
*DsbB in DPC micelles: E. coli, NMR Structure* w. bound ubiquinone: 2K74	2K73	Zhou et al. (2008)
*Vitamin K epoxide reductase: Synechococcus sp.* (expressed in E. coli), 3.60 Å**	3KP9	Li et al. (2010)
Mo/W bis-MGD Oxidoreductases
*Polysulfide Reductase PsrABC (native): Thermus thermophilus, 2.4 Å* w. bound quinone inhibitor PCP, 2.5 Å: 2PVY w. bound menaquinone, 3.1 Å: 2PVW w. bound quinone, 3.1 Å: 2PVX	2VPZ	Jormakka et al. (2008)
Electron Transport Chain Complexes: Complex I
*Complex I membrane domain: Escherichia coli, 3.90 Å*	3M9C	Efremov et al. (2010)
*Complex I complete: Thermus thermophilus, 4.50 Å*	3M9S	Efremov et al. (2010)
Electron Transport Chain Complexes: Complex II
*Fumarate Reductase Complex: Escherichia coli, 3.3 Å* This structure has been replaced by 1L0V, below.	1FUM	Iverson et al. (1999)
*Native Fumarate Reductase Complex: Escherichia coli, 3.3 Å* +HQNO, 2.7 Å, 1KF6. +DNP-19, 3.6 Å, 1KFY	1L0V	Iverson et al. (2002)
*Fumarate Reductase Complex: Wolinella succinogenes, 1.78 Å* 2BS2 has small unit cell. 1QLB, 2.2 Å, has a larger unit cell.	2BS2	Lancaster et al. (1999)
*Formate dehydrogenase-N: Escherichia coli, 1.6 Å (native structure)* HQNO complex, 2.8 Å: 1KQG	1KQF	Jormakka et al. (2002)
*Succinate dehydrogenase (Complex II): Escherichia coli, 2.6 Å* DNP-17 Complex, 2.9 Å: 1NEN	1NEK	Yankovskaya et al. (2003)
*Succinate dehydrogenase (Complex II) with Atpenin A5: Escherichia coli, 3.10 Å*	2ACZ	Horsefield et al. (2006)
*Succinate:ubiquinone oxidoreductase (SQR, Complex II): porcine heart mitochondria, 2.4 Å* with inhibitors, 3.5 Å: 1ZP0	1ZOY	Sun et al. (2005)
*Succinate:ubiquinone oxidoreductase (SQR, Complex II) w. carboxin inhibitor: chicken heart mitochondria, 2.1 Å* with 3-nitropropionic acid (3-NP) inhibitor, 2.33 Å: 1YQ4 with OAA inhibitor, 2.2 Å: 1YQ3	2FBW	Huang et al. (2006)
*Succinate:ubiquinone oxidoreductase (SQR, Complex II) with TEO at the active site: chicken heart mitochondria, 1.74 Å* with bound malonate at the active site, 2.40 Å: 2H89	2H88	Huang et al. (2006)
Electron Transport Chain Complexes: Complex III (Cytochrome bc₁) ( Information about Cytochrome bc₁)
*Cytochrome bc₁: Bos taurus, 2.7 Å* Bovine heart mitochondria, 5 subunits	1QCR	Xia et al. (1997)
*Cytochrome bc₁: Bos taurus, 3.0 Å* Bovine Heart Mitochondria, 11 subunits.	1BGY	Iwata et al. (1998)
*Cytochrome bc₁: Bos taurus, 2.26 Å* Bovine Heart Mitochondria, with jg144 inhibitor	2FYU	Esser et al. (2006)
*Cytochrome bc₁: Bos taurus, 2.40 Å* Bovine Heart Mitochondria, without ubiquinone. w. ubiquinone, 2.60 Å: 1NTZ w. antimycin A₁, 2.60 Å: 1NTK w. NQNO, 3.2 Å: 1NU1	1NTM	Gao et al. (2003)
*Cytochrome bc₁: Bos taurus, 2.60 Å* Bovine Heart Mitochondria, w. stigmatellin w. azoxystrobin, 2.69 Å: 1SQB w. myxothiazol, 2.70 Å: 1SQP w. MOAS, 3.00 Å: 1SQQ w. UHDBT, 2.85 Å: 1SQV	1SQX	Esser et al. (2004)
*Cytochrome bc₁: Bos taurus, 2.10 Å* Bovine Heart Mitochondria, w. bound antimycin without antimycin, 2.10 Å: 1PP9 with bound stigmatellin, 2.10 Å: 2A06	1PPJ	Huang et al. (2005)
*Cytochrome bc₁: Gallus gallus, 3.16 Å* Chicken Heart Mitochondria (native structure) w. bound stigmatellin, 3.5 Å: 2BCC w. bound stigmatellin and antimycin, 3.7 Å: 3BCC	1BCC	Zhang et al. (1998)
*Cytochrome bc₁: Sarcomyces cerevisiae, 2.3 Å* yeast, 9 subunits.	1EZV	Hunte et al. (2000)
*Cytochrome bc₁: Sarcomyces cerevisiae, 2.3 Å* With phospholipids.	1KB9	Lange et al. (2001)
*Cytochrome bc₁: Sarcomyces cerevisiae, 2.5 Å* With HHDBT inhibitor.	1P84	Palsdottir et al. (2003)
*Cytochrome bc₁: Sarcomyces cerevisiae, 2.3 Å* With bound stigmatellin.	2IBZ	Lancaster et al. (2007)
*Cytochrome bc₁: Sarcomyces cerevisiae, 1.9 Å* With bound isoform-1 cytochrome c. With bound isoform-2 cytochrome c, 2.50 Å: 3CXH	3CX5	Solmaz & Hunte (2008)
*Cytochrome bc₁: Rhodobacter Sphaeroides, 3.20 Å*	2FYN	Esser et al. (2006)
*Cytochrome bc₁: Rhodobacter capsulatus, 3.50 Å*	1ZRT	Berry et al. (2004)
Electron Transport Chain Complexes: Cytochrome b₆f of Oxygenic Photosynthesis
*Cytochrome b₆f complex: Mastigocladus laminosus, 3.0 Å* (Original PDB file 1UM3 replaced by 1VF5)	1VF5	Kurisu et al. (2003)
*Cytochrome b₆f complex: Mastigocladus laminosus, 3.80 Å* In complex with quinone analogue inhibitor DBMIB.	2D2C	Yan et al. (2006)
*Cytochrome b₆f complex, native structure: Mastigocladus laminosus, 3.00 Å* In complex with NQNO, 3.55 Å: 2E75 In complex with TDS, 3.41 Å: 2E76	2E74	Yamashita et al. (2007)
*Cytochrome b₆f complex: Chlamydomonas reinhardtii, 3.1 Å*	1Q90	Stroebel et al. (2003)
*Cytochrome b₆f complex: Nostoc* sp. PCC 7120, 3.0 Å**	2ZT9	Baniulis et al. (2010)
Electron Transport Chain Complexes: Complex IV (Cytochrome C Oxidase) ( Information about cytochrome c oxidases )
*Cytochrome C Oxidase, aa₃: Bos taurus* (bovine) heart mitochndria, 2.8 Å**	1OCC	Tsukihara et al. (1996)
*Fully Oxidized Cytochrome C Oxidase, aa₃: Bos taurus* (bovine) heart mitochndria, 1.80 Å** Fully reduced form, 1.90 Å: 1V55	1V54	Tsukihara et al. (2003)
*Cytochrome C Oxidase, aa₃: Paracoccus denitrificans, 2.70 Å*	1AR1	Iwata et al. (1995) Ostermeier et al. (1997)
*Cytochrome C Oxidase, aa₃, Fully Oxidized: Paracoccus denitrificans, 3.00 Å*	1QLE	Harrenga & Michel H (1999)
*Cytochrome C Oxidase, aa₃, N131D variant: Paracoccus denitrificans, 2.32 Å*	3EHB	Dürr et al. (2008)
*Cytochrome C Oxidase, aa₃: Paracoccus denitrificans, 2.25 Å*	3HB3	Koepke et al. (2009)
*Cytochrome Oxidase, cbb₃: Pseudomonas stutzeri, 3.2 Å*	3MK7	Buschmann et al. (2010)
*Cytochrome ba₃: Thermus thermophilus, 2.4 Å*	1EHK	Soulimane et al. (2000)
*Cytochrome ba₃ with bound xenon: Thermus thermophilus, 3.37 Å*	3BVD	Luna et al. (2008)
*Cytochrome C Oxidase wild-type: Rhodobacter sphaeroides, 2.30 Å* EQ(I-286) mutant, 3.00 Å: 1M57	1M56	Svensson-Ek et al. (2002)
*Cytochrome C Oxidase, two-subunit catalytic core: Rhodobacter sphaeroides, 2.0 Å*	2GSM	Qin et al. (2006)
*Ubiquinol Oxidase, cytochrome bo₃: E. coli, 3.5 Å*	1FFT	Abramson et al. (2000)
Nitric Oxide Reductases
*Nitric Oxide Reductase: Pseudomonas aeruginosa, 2.70 Å* Crystallized with cNOR antibody (Fab)	3O0R	Hino et al. (2010)
Photosystems
*Photosystem I: Thermosynechococcus elongatus, 4.0 Å*	2PPS	Schubert et al. (1997)
*Photosystem I: Thermosynechococcus elongatus, 2.5 Å*	1JB0	Jordan et al. (2001)
*Photosystem I (plant): Psium sativum, 3.4 Å*	2O01	Amunts et al. (2007)
*Photosystem II: Thermosynechococcus elongatus, 3.8 Å*	1FE1	Zouni et al. (2001)
*Photosystem II: Thermosynechococcus elongatus, 3.5 Å* Resolution sufficient to reveal oxygen-evolving center.	1S5L	Ferreira et al. (2004)
*Photosystem II: Thermosynechococcus elongatus, 3.0 Å* Shows locations of 77 cofactors per monomer and provides info on Mn₄Ca cluster.	2AXT	Loll et al. (2005)
*Photosystem II: Thermosynechococcus elongatus, 2.9 Å* Includes all 20 protein subunits and all 35 chlorophyll a molecules. Part 2 of coördinate file: 3BZ2	3BZ1	Guskov et al. (2009)
*Photosystem II: Thermocynechococcus vulcanus, 3.7 Å*	1IZL	Kamiya & Shen (2003)
*Photosystem II, Br-substituted: Thermocynechococcus vulcanus, 3.7 Å* Br-substitution reveals location of chlorides. I-substituted, 4.0 Å: 3A0H	3A0B	Kawakami et al. (2009)
Light-Harvesting Complexes
*Light-Harvesting Complex: Rhodopseudomonas acidophila, 2.0 Å* R-free = 0.190. 1KZU, 2.5 Å R-free = 0.252	1NKZ	Papiz et al. (2003)
*Light-Harvesting Complex: Rhodospirillum molischianum, 2.4 Å*	1LGH	Koepke et al. (1996)
*Light-Harvesting Complex LHC-II, Spinach Photosystem II: Spinacia oleracia, 2.72 Å*	1RWT	Liu et al. (2004)
*Light-Harvesting Complex CP29, Spinach Photosystem II: Spinacia oleracia, 2.80 Å*	3PL9	Pan et al. (2011)
*Light-Harvesting Complex LHC-II, Pea Photosystem II: Pisum sativum, 2.50 Å*	2BHW	Standfuss et al. (2005)
Photosynthetic Reaction Centers
*Photosynthetic Reaction Center: Blastochloris viridis, 2.3 Å* The first high-resolution crystallographic structure of a membrane protein Former species name: Rhodopseudomonas virdis	1PRC	Deisenhofer et al. (1985) [not in PubMed]
*Photosynthetic Reaction Center: Blastochloris viridis, 1.86 Å* Lipidic sponge-phase structure. Reveals lipids on protein surface. Low x-ray dose structure, 1.95 Å: 2WJM	2WJN	Wöhri et al. (2009)
*Photosynthetic Reaction Center: Rhodobacter sphaeroides, 3.0 Å*	1PSS	Yeates et al. (1987)
*Photosynthetic Reaction Center: Rhodobacter sphaeroides, 3.1 Å*	2RCR	Chang et al. (1991)
*Photosynthetic Reaction Center: Rhodobacter sphaeroides* (dark state), 2.2 Å** Illuminated state, 2.60 Å 1AIG	1AIJ	Stowell et al. (1997)
*Photosynthetic Reaction Center: Rhodobacter sphaeroides, 2.35 Å* Lipidic cubic phase crystallization.	1OGV	Katona et al. (2003)
*Photosynthetic Reaction Center: Rhodobacter sphaeroides, 1.87 Å* pH 8 neutral state. pH 8 charge-separated state, 2.07 Å: 2J8D	2J8C	Koepke et al. (2007)
*Photosynthetic Reaction Center: Thermochromatium tepidum, 2.2 Å*	1EYS	Nogi et al. (2000)

Description of Table

The table above provides useful information about integral membrane proteins whose crystallographic, or sometimes NMR, structures have been determined to a resolution sufficient to identify TM helices of helix-bundle membrane proteins (typically 4 - 4.5 Å). It is based upon Preusch et al. (1998) as revised by White & Wimley (1999). Reference is made to all of the protein types whose structures have been determined. We have attempted to make the database as inclusive as possible. If you find errors or omissions, please send a message to .

Search the PDB at the Research Collaboratory for Structural Bioinformatics (RCSB)

References

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from the Stephen White laboratory at UC Irvine