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Independent gating of single pores in CLC-0 chloride channels

Item Type:Article
Title:Independent gating of single pores in CLC-0 chloride channels
Creators Name:Ludewig, U., Pusch, M. and Jentsch, T.J.
Abstract:The Cl- channel from the Torpedo electric organ, CLC-0, is the prototype of a large gene family of Cl- channels. At the single-channel level, CLC-0 shows a "double-barreled" behavior. Recently it was shown that CLC-0 is a dimer, and it was suggested that each subunit forms a single pore. The two protopores are gated individually by a fast voltage and anion-dependent gating mechanism. A slower common gating mechanism operates on both pores simultaneously. Previously, wild-type/mutant heteromeric channels had been constructed that display a large wild-type pore and small mutant pore. Here we use patch-clamp recording of single wild-type and mutant CLC-0 channels to investigate in detail the dependence of the gating of one protopore on the physically attached neighboring pore. No difference in rate constants of opening and closing of protopores could be found comparing homomeric wild-type and heteromeric wild-type/mutant channels. In addition, detailed kinetic analysis reveals that gating of single subunits is not correlated with the gating of the neighboring subunit. The results are consistent with the view that permeation and fast gating of individual pores are fully independent of the neighboring pore. Because the two subunits are associated in a common protein complex, opening and closing transitions of individual pores are probably due to only small conformational changes in each pore. In addition to the fast and slow gating mechanisms known previously for CLC-0, in the course of this study we occasionally observed an additional gating process that led to relatively long closures of single pores.
Keywords:Chloride Channels, Dimerization, Electric OrganIon Channel Gating, Kinetics, Macromolecular Substances, Membrane Potentials, Biological Models, Site-Directed Mutagenesis, Patch-Clamp Techniques, Point Mutation, Recombinant Proteins, Torpedo, Animals
Source:Biophysical Journal
Publisher:Biophysical Society
Page Range:789-797
Date:August 1997
Official Publication:https://doi.org/10.1016/S0006-3495(97)78111-6
PubMed:View item in PubMed

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