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Pore stoichiometry of a voltage-gated chloride channel

Nature volume 394, pages 687–690 (1998)Cite this article

Abstract

Ion channels allow ions to pass through cell membranes by forming aqueous permeation pathways (pores). In contrast to most known ion channels, which have single pores, a chloride channel belonging to the ClC family1 (Torpedo ClC-0) has functional features that suggest that it has a unique ‘double-barrelled’ architecture in which each of two subunits forms an independent pore. This model is based on single-channel recordings of ClC-0 that has two equally spaced and independently gated conductance states2,3,4. Other ClC isoforms do not behave in this way5,6, raising doubts about the applicability of the model to all ClC channels. Here we determine the pore stoichiometry of another ClC isoform, human ClC-1, by chemically modifying cysteines that have been substituted for other amino acids located within the ClC ion-selectivity filter7. The ClC-1 channel can be rendered completely susceptible to block by methanethiosulphonate reagents when only one of the two subunits contains substituted cysteines. Thiol side chains placed at corresponding positions in both subunits can form intersubunit disulphide bridges and coordinate Cd2+, indicating that the pore-forming regions from each subunit line the same conduction pathway. We conclude that human ClC-1 has a single functional pore.

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Figure 1: Possible configurations of hClC-1 channels with cysteine substitutions in pore-forming segments of one or both subunits.
Figure 2: MTS-mediated modification of heterodimeric single-cysteine-substituted hClC-1 channels.
Figure 3: Formation of disulphide bridges between two Cys 231 sidechains.
Figure 4: Dose–response curves for Cd2+ block.

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Acknowledgements

We thank L. DeFelice, P. Hidalgo, M. Holmgren, R. Horn, J. P. Johnson, N. Mitrovic and C. I. Petersen for discussions and review of the manuscript. This work was supported by the Deutsche Forschungsgemeinschaft (Ch.F.), the Muscular Dystrophy Association (Ch.F., A.L.G.) and the National Institutes of Health (A.L.G.).

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  1. Departments of Medicine (Nephrology) and Pharmacology, and The Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville, 37232-6600, Tennessee, USA

    Christoph Fahlke, Thomas H. Rhodes, Reshma R. Desai & Alfred L. George Jr

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  1. Christoph Fahlke
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Correspondence to Christoph Fahlke.

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Fahlke, C., Rhodes, T., Desai, R. et al. Pore stoichiometry of a voltage-gated chloride channel. Nature 394, 687–690 (1998). https://doi.org/10.1038/29319

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