Table 1.
Crystal structures of ABC transporters
| Name (organism) | Remarks | Substrate bound | Resolution (Å) | PDB accession no. | Reference |
| Type I importers | |||||
| Molybdate transporter ModB2C2-A complex (Archaeoglobus fulgidus) | Inward-facing conformation, with SBP bound | Mg2+, PO43-, WoO42− | 3.10 | 2ONK | Hollenstein et al., 2007 |
| ModBC (Methanosarcina acetivorans) | Inward-facing conformation, without SBP bound, in a trans-inhibited state | Mg2+, WoO42− | 3.00 | 3D31 | Gerber et al., 2008 |
| MalFGK2-MBP maltose uptake transporter (E. coli) | Outward-facing conformation stabilized by a mutation in the NBDs (MalK E159Q), with MBP | Maltose, ATP | 2.80 | 2R6G | Oldham et al., 2007 |
| MalFGK2 maltose uptake transporter (E. coli) | TM helix 1 deleted, in inward-facing conformation, in resting state, without MBP | — | 4.50 | 3FH6 | Khare et al., 2009 |
| MalFGK2-MBP maltose uptake transporter (E. coli) | Pre-translocation intermediate state, with mutations in MBP (G69C/S337C) that stabilize the substrate-bound closed conformation by a cross-link | AMP-PNP, Mg2+, maltose | 2.90 | 3PUZ | Oldham and Chen, 2011a |
| Outward-facing conformation state, with MBP | AMP-PNP, Mg2+, maltose | 3.10 | 3PUY | ||
| Pre-translocation intermediate state, with mutations in MBP (G69C/S337C) that stabilize the substrate-bound closed conformation by a cross-link | Maltose | 3.10 | 3PV0 | ||
| MalFGK2-MBP maltose uptake transporter (E. coli) | Outward-facing conformation, with MBP | AMP-PNP, Mg2+, maltose | 2.20 | 3RLF | Oldham and Chen, 2011b |
| Outward-facing conformation, with MBP | ADP · VO43−, Mg2+, maltose | 2.40 | 3PUV | ||
| Outward-facing conformation, with MBP | ADP · AlF4−, Mg2+, maltose | 2.30 | 3PUW | ||
| Outward-facing conformation, with MBP | ADP · BeF3−, Mg2+, maltose | 2.30 | 3PUX | ||
| MalFGK2-MBP maltose uptake transporter (E. coli) | Complex with its regulatory protein EIIAglc, inward-facing conformation | — | 3.91 | 4JBW | Chen et al., 2013 |
| MalFGK2-MBP maltose uptake transporter (E. coli) | Outward-facing conformation, with MBP | Maltoheptaose | 2.90 | 4KHZ | Oldham et al., 2013 |
| Outward-facing conformation, with MBP | ANP, α-d-glycose | 2.38 | 4KI0 | ||
| MetNI methionine uptake transporter (E. coli) | Inward-facing conformation | — | 3.70 | 3DHW | Kadaba et al., 2008 |
| Inward-facing conformation, at higher resolution (detergent Cymal5) | ADP | 2.90 | 3TUI | Johnson et al., 2012 | |
| Inward-facing conformation, C2 domains repositioned (detergent decylmaltoside) | — | 4.00 | 3TUJ | ||
| Type II importers | |||||
| BtuC2D2 vitamin B12 transporter (E. coli) | Outward-facing conformation, no SBP bound | V4O124− | 3.20 | 1L7V | Locher et al., 2002 |
| BtuC2D2-F complex (E. coli) | BtuC in asymmetric conformation. The translocation pore is closed from both sites. BtuF is in an open state. | — | 2.60 | 2QI9 | Hvorup et al., 2007 |
| BtuC2D2-F complex (E. coli) | Intermediate occluded state, nucleotide bound | AMP-PNP | 3.47 | 4FI3 | Korkhov et al., 2012b |
| BtuC2D2-F complex (E. coli) | E159Q mutation in NBD abolished ATP hydrolysis activity, BtuC in asymmetric conformation. The translocation pore is closed from both sites. | — | 3.49 | 4DBL | Korkhov et al., 2012a |
| HI1470/1471 putative metal chelate–type ABC transporter (H. influenzae) | Inward-facing conformation, without SBP, renamed MolB2C2 (as later was shown to bind WoO42−/MoO42−) | — | 2.40 | 2NQ2 | Pinkett et al., 2007 |
| HmuU2V2 heme transporter (Yersinia pestis) | Outward-facing conformation | — | 3.00 | 4G1U | Woo et al., 2012 |
| ECF-type importers | |||||
| RibU S-component for riboflavin (S. aureus) | Substrate bound | Riboflavin | 3.60 | 3P5N | Zhang et al., 2010 |
| ThiT S-component for thiamin (L. lactis) | Substrate bound | Thiamin | 2.00 | 3RLB | Erkens et al., 2011 |
| BioY S-component for biotin (L. lactis) | Substrate bound | Biotin | 2.10 | 4DVE | Berntsson et al., 2012 |
| NikM S-component for Ni2+ (Thermoanaerobacter tengcongensis) | Substrate bound | Ni2+/Co2+ | 1.83–2.5 | — | Yu et al., 2013 |
| ECF-FolT transporter (L. brevis) | Substrate free, inward-facing conformation | — | 3.00 | 4HUQ | Xu et al., 2013 |
| ECF-HmpT transporter (L. brevis) | Substrate free, inward-facing conformation | — | 3.53 | 4HZU | Wang et al., 2013 |
| Exporters | |||||
| Sav18662 multidrug transporter (S. aureus) | Outward-facing conformation | ADP | 3.00 | 2HYD | Dawson and Locher, 2006 |
| Outward-facing conformation | AMP-PNP | 3.40 | 2ONJ | Dawson and Locher, 2007 | |
| Heterodimeric ABC transporter TM287-TM288 (T. maritima) | Inward-facing conformation | AMP-PNP | 2.90 | 3QF4 | Hohl et al., 2012 |
| MsbA2 lipid “flippase” (Salmonella typhimurium) | Outward-facing conformation, with nucleotide bound | ANP-PNP | 4.50 | 3B5Y | Ward et al., 2007 |
| Outward-facing conformation, with nucleotide bound | ANP-PNP | 3.70 | 3B60 | ||
| Outward-facing conformation, with nucleotide bound | ADP, VO43− | 4.20 | 3B5Z | ||
| MsbA2 lipid “flippase” E. coli | Inward-facing conformation, open apo structure | — | 5.30 | 3B5W | |
| MsbA2 lipid “flippase” Vibrio cholera | Inward-facing conformation, closed apo structure | — | 5.50 | 3B5X | |
| Multidrug transporter P-glycoprotein (Mus musculus) | Inward-facing conformation | — | 3.80 | 3G5U | Aller et al., 2009 |
| Inward-facing conformation | Cyclic-tris-(R)-valineselenazole | 4.40 | 3G60 | ||
| Inward-facing conformation | Cyclic-tris-(S)-valineselenazole | 4.35 | 3G61 | ||
| Re-refined, inward-facing conformation | — | 3.80 | 4M1M | Li et al., 2014 | |
| Multidrug transporter P-glycoprotein (Caenorhabditis elegans) | Inward-facing conformation | — | 3.40 | 4F4C | Jin et al., 2012 |
| ABCB10 mitochondrial ABC transporter (Homo sapiens) | Inward-facing conformation | AMPPCP | 2.85 | 4AYT | Shintre et al., 2013 |
| Inward-facing conformation; different crystal form (rod/plate) | AMP-PCP/AMP-PNP | 2.90/3.30 | 4AYX/4AYW | ||
| Inward-facing conformation | — | 2.85 | 3ZDQ | ||
SBP, substrate-binding protein; MBP, maltose-binding protein; outward and inward facing, the translocation pathway in the TMDs exposed to the trans-side or the cis-side of the membrane, respectively.