Abstract

Ion channels have historically been viewed as distinct from secondary active transporters. However, the recent discovery that the CLC 'chloride channel' family is made up of both channels and active transporters has led to the hypothesis that the ion-transport mechanisms of these two types of membrane proteins may be similar. Here we use single-channel analysis to demonstrate that ClC-0 channel gating (opening and closing) involves the transmembrane movement of protons. This result indicates that ClC-0 is a 'broken' Cl^-/H⁺ antiporter in which one of the conformational states has become leaky for chloride ions. This finding clarifies the evolutionary relationship between the channels and transporters and conveys that similar mechanisms and analogous protein movements are used by both.

1. Stanford University, Department of Molecular and Cellular Physiology, 279 Campus Drive, Stanford, California 94305, USA.

Correspondence to: Merritt Maduke¹ e-mail: maduke@stanford.edu

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