Molecular determinants of common gating of a ClC chloride channel.
Uniquely, the ClC family harbours dissipative channels and anion/H(+) transporters that share unprecedented functional characteristics. ClC-1 channels are homodimers in which each monomer supports an identical pore carrying three anion-binding sites. Transient occupancy of the extracellular binding site by a conserved glutamate residue, E232, independently gates each pore. A common gate, the molecular basis of which is unknown, closes both pores simultaneously. Mutations affecting common gating underlie myotonia congenita in humans. Here we show that the common gate likely occludes the channel pore via interaction of E232 with a highly conserved tyrosine, Y578, at the central anion-binding site. We also identify structural linkages important for coordination of common gating between subunits and modulation by intracellular molecules. Our data reveal important molecular determinants of common gating of ClC channels and suggest that the molecular mechanism is an evolutionary vestige of coupled anion/H(+) transport.
Biota Structural Biology Laboratory and ACRF Rational Drug Discovery Centre, St Vincent's Institute of Medical Research, Fitzroy, Victoria 3065, Australia.
Brett
B
Bennetts
Michael W
MW
Parker
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001665:Binding Sites; D018118:Chloride Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism*; D019143:Evolution, Molecular; D015870:Gene Expression; D018698:Glutamic Acid / Q000737:chemistry* / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating; D008958:Models, Molecular; D018408:Patch-Clamp Techniques; D011485:Protein Binding; D055503:Protein Multimerization; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014101:Torpedo / Q000378:metabolism; D014443:Tyrosine / Q000737:chemistry* / Q000378:metabolism
C086321:CLC-1 channel; D018118:Chloride Channels; D002712:Chlorides; D021122:Protein Subunits; D018698:Glutamic Acid; D014443:Tyrosine