Abstract

Functional and structural studies demonstrate that Cl- channels of the ClCfamily have a dimeric double-barrelled structure, with each monomer contributing an identical pore. Studies with ClC-0, the prototype ClC channel, show the presence of independent mechanisms gating the individual pores or both pores simultaneously. A single-pointmutation in the CBS-2 domain of ClC-0 has been shown to abolish slow gating.We have taken advantage of the high conservation of CBSdomains in ClC channels to test for the presence of a slowgate inClC-2 by reproducing this mutation (H811A). ClC-2-H811A showed faster opening kinetics and opened at more positive potentials than ClC-2. There was no difference in [Cl-]i dependence. Additional neutralization of a putative pore gate glutamate side chain (E207V) abolished all gating. Resolving slow and fast gating relaxations, however, revealed that the H811A mutation affected both fast and slow gating processes in ClC-2. This suggests that slow and fast gating in ClC-2 are coupled, perhaps with slow gating contributing to the operation of the pore E207 as a protopore gate. © 2006 The Authors. Journal compilation © 2006 The Physiological Society.