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Pore-forming segments in voltage-gated chloride channels

Abstract

The ability to differentiate between ions is a property of ion channels that is crucial for their biological functions1. However, the fundamental structural features that define anion selectivity and distinguish anion-permeable from cation-permeable channels are poorly understood. Voltage-gated chloride (Cl) channels belonging to the ClC family are ubiquitous and have been predicted to play important roles in many diverse physiological2 and pathophysiological3,4,5 processes. We have identified regions of a human skeletal muscle ClC isoform that contribute to formation of its anion-selective conduction pathway. A core structural element (P1 region) of the ClC channel pore spans an accessibility barrier between the internal and external milieu, and contains an evolutionarily conserved sequence motif: GKxGPxxH. Neighbouring sequences in the third and fifth transmembrane segments also contribute to isoform-specific differences in anion selectivity. The conserved motif in the Clchannel P1 region may constitute a ‘signature’ sequence for an anion-selective ion pore by analogy with the homologous GYG sequence that is essential for selectivity in voltage-gated potassium ion (K+) channel pores6,7,8.

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Figure 1: Evolutionary conservation of the GKEGPFVH motif in P1, and the effect of mutations.
Figure 2: Substituted cysteine accessibility experiments of P1 region.
Figure 3: Substituted cysteine accessibility experiments of D5 and revised transmembrane topology for the ClC channel pore.

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Acknowledgements

We thank S. Uchida for providing rat ClC-3, M. Akabas for helpful discussions, L. Limbird and D. Snyders for critical reviews of the manuscript. We also thank R. Desai and C. Ryan for technical assistance. This work was supported by the Muscular Dystrophy Association (A.L.G., Ch.F.), the Lucille P. Markey Charitable Trust (A.L.G.) and the German Research Foundation (Ch.F.). C.L.B. is a recipient of the Luis and Emma Benzak Neuromuscular Disease Research Fellowship from the Muscular Dystrophy Association. H.T.Y. is a recipient of a National Kidney Foundation Research Fellowship.

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Correspondence to Alfred L. George Jr.

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Fahlke, C., Yu, H., Beck, C. et al. Pore-forming segments in voltage-gated chloride channels. Nature 390, 529–532 (1997). https://doi.org/10.1038/37391

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