PMID:15165864
| Citation |
Faraldo-Gómez, JD and Roux, B (2004) Electrostatics of ion stabilization in a ClC chloride channel homologue from Escherichia coli. J. Mol. Biol. 339:981-1000 |
|---|---|
| Abstract |
The structural determinants of electrostatics of ion stabilization within EcClC, a ClC-type chloride channel homologue from Escherichia coli, are studied using a continuum dielectric approximation. Specifically, the ion occupancy is investigated in the wild-type protein and a mutant thereof, and the contribution to the electrostatic binding free energy of local and non-local interactions is characterized at the single-residue level. This analysis shows that, in spite of the desolvation cost and the strong ion-ion repulsion, all previously reported binding sites can be occupied simultaneously. The stabilizing effect of the protein arises from hydrogen bonding as well as from longer-range favorable interactions, such as with the strictly conserved Lys131 side-chain. The latter is involved in the stabilization of the conserved GSGIP motif that delimits two of the binding sites. Interestingly, an additional low-affinity binding site, mediated by a structurally analogous motif including the side-chain of Arg340, can be identified on the extracellular side of the permeation pathway. Finally, it is shown that, in contrast to K-channels, and in analogy to the SBP/PBP sulfate/phosphate-binding proteins, the contribution of helix macrodipoles to chloride binding in EcClC is only marginal. |
| Links |
PubMed Online version:10.1016/j.jmb.2004.04.023 |
| Keywords |
Amino Acid Sequence; Chloride Channels/chemistry; Crystallography, X-Ray; Escherichia coli/chemistry; Models, Molecular; Molecular Sequence Data; Protein Conformation; Sequence Homology, Amino Acid; Static Electricity |
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