Pore-forming segments in voltage-gated chloride channels.
The ability to differentiate between ions is a property of ion channels that is crucial for their biological functions. 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 physiological and pathophysiological 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 Cl- channel 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 pores.[1]References
- Pore-forming segments in voltage-gated chloride channels. Fahlke, C., Yu, H.T., Beck, C.L., Rhodes, T.H., George, A.L. Nature (1997) [Pubmed]
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