Add the Base, Close the Gate

Science's STKE  08 Apr 2003:
Vol. 2003, Issue 177, pp. tw139-TW139
DOI: 10.1126/stke.2003.177.tw139

Members of the chloride channel family ClC are present in organisms ranging from bacteria to animals. In ClC channels, ion conduction and gating are tightly coupled. Dutzler et al. compared their structures of wild-type and mutant Escherichia coli ClC channels and found that a glutamate residue acts as a gate. When it is unprotonated, the glutamate side chain occupies a chloride ion-binding site and closes the channel. However, when it is protonated, the side chain flips out of the way, and the channel opens. Thus, extracellular pH can regulate gating. The open channel contains a queue of three chloride ions, not unlike the ion pathway in the structurally distinct potassium channel.

R. Dutzler, E. B. Campbell, R. MacKinnon, Gating the selectivity filter in ClC chloride channels. Science 300, 108-112 (2003). [Abstract] [Full Text]