Table 1|.
Set of available PDB structures of CLC-ec1 at various conditions. The RMSD values are calculated for backbone atoms with respect to the PDB 1OTS structure as reference.
| PDB ID | PH | Mutations | Ions | BB RMSD (Å) |
|---|---|---|---|---|
| 1OTS | 9.5 | NaCI | reference | |
| 1KPK | 8.5 | Na2SO4 / Li2SO4 | 0.785 | |
| 1KPL* | 4.6 | M26L/C264V | Na2SO4 / Li2SO4 | 1.169 |
| 1OTT | 9.5 | E148A | NaCI | 0.465 |
| 1OTU | 9.5 | E148Q | NaCI | 0.589 |
| 2EXY | 8.5 | E148Q | TART | 0.646 |
| 2EZ0 | 9.5 | S107A/E148Q/Y445A | NaBr | 0.722 |
| 2FEC | 7.5 | E203Q | NaBr | 0.425 |
| 2FED | 7.5 | E203Q | NaCI | 0.427 |
| 2FEE | 7.5 | NaBr | 0.362 | |
| 2H2P | 7.5 | KSCN | 0.515 | |
| 2H2S | 7.5 | E148A | KSeCN | 0.491 |
| 2HLF | 9.5 | Y445E | NaBr | 0.378 |
| 2HT2 | 8.5 | Y445H | TART | 0.654 |
| 2HT3 | 7.5 | Y445L | TART | 0.581 |
| 2HT4 | 8.0 | Y445W | NaBr | 0.533 |
| 2HTK | 8.5 | Y445A | TART | 0.378 |
| 2R9H | 9.5 | Q207C | NaCI / TART | 0.558 |
| 3DET | 5.5 | E148A / Y445A | KCI | 0.415 |
| 3EJY | 9.5 | NaBr | 0.425 | |
| 3EJZ | 8.5 | E203V | NaBr | 0.426 |
| 3NMO† | 9.5 | LiNO3 | 0.565 | |
| 4ENE | 8.5 | CaCI2 | 0.442 | |
| 4FTP | 9.5 | E202Y | 0.877 | |
| 4KJP | 9.5 | 0.412 | ||
| 4KK5 | 9.0 | NaF / NaBr | 0.282 | |
| 4KK8 | 8.5 | E148Q | NaF | 0.422 |
| 4KKB | 7.0 | E148A | NaF / NaBr | 0.454 |
| 4KKC | 9.0 | E148A | NaBr | 0.679 |
| 5HD8 | 9.0 | D417C | TART | 0.597 |
Denotes a low-pH structure of CLC from Salmonella typhimurium.
Denotes structures of monomers. All CLC X-ray structures exhibited essentially identical conformations. However, NMR, computational and biochemical studies have suggested larger-scale movements. A recent X-ray structure of a ClC-ec1 triple mutant (E148Q/E203Q/E113Q) that mimics the protonation of essential glutamates at low pH, reports global conformational changes that lead to opening of the extracellular permeation pathway.45 Thus, under the assumption that the displacements of surface features are signatures of movements in the underlying helices, our LAFM maps suggest motions that could result in changes in the region of the extracellular gate.