Molecular determinants of common gating of a ClC chloride channel

Abstract

Uniquely, the ClC family harbours dissipative channels and anion/H þ 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 þ transport.

The analysis of myotonia congenita mutations discloses functional clusters of amino acids within the CBS2 domain and the C-terminal peptide of the ClC-1 channel

“…To describe the position of the MC ClC‐1 mutations in Figure , we used the homology model of the dimeric ClC‐1 channel based on the crystallographic coordinates of the eukaryotic Cl‐/H+ exchanger CmClC (PDB id: 3ORG; Bennetts & Parker, ; Feng, Campbell, Hsiung, & MacKinnon, ).…”

ClC‐1 mutations in myotonia congenita patients: insights into molecular gating mechanisms and genotype–phenotype correlation

“…; Ma et al . ; Bennetts & Parker, ). A recent report proposed that slow channel closure may depend on the H‐bond interaction established by E232 of pore helix F and Y578 of helix R (Bennetts & Parker, ).…”

Probing the conformation of a conserved glutamic acid within the Cl− pathway of a CLC H+/Cl− exchanger

“…Several lines of evidence, stemming from computational (Bisset et al, 2005) and experimental work on CLC channels (Traverso et al, 2006) and transporters (Zifarelli et al, 2012), suggest that Glu ex can occupy the central cavity. However, in the CLC-0 and -1 channels, interactions between Glu ex and Tyr cen were proposed to occur (Bennetts and Parker, 2013) during the common gating process rather than during gating of the individual pores, as would be expected if this state occurred during the transport cycle. Therefore, the issue of whether a cmCLC-like state is part of the exchange cycle remains an open question.…”