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Structural studies of ion selectivity in tetrameric cation channels

The Rockefeller University Press
Publication Date
DOI: 10.1085/jgp.201010546
  • Perspective
  • Biology
  • Chemistry
  • Medicine


The Rockefeller University Press J. Gen. Physiol. Vol. 137 No. 5 397–403 397 P e r s p e c t i v e Introduction The transfer of ions across biological membranes is central to physiological processes like nerve excitation, muscle cell contraction, and hormone secretion. To this end, ion channels play a vital role by providing passage- ways, the ion conduction pores, within membranes to allow specific ions to traverse down their concentration gradients. This ability to select for specific ionic species is known as ion selectivity and is a fundamental property defining ion channel function. In tetrameric cation channels, the largest and best characterized superfam- ily of ion channels, selectivity arises from the unique structural and chemical environment within part of the ion channel pore known as the selectivity filter. Our un- derstanding of the molecular details governing ion se- lectivity in this group of channels has come a long way with the advancement of genetic, biochemical, and electrophysiological analysis of ion channels and, more recently, the structural characterization of several of them. Here, we review the contributions made by ion channel structural biology, specifically the determination of high resolution crystal structures of various tetrameric cation channels, beginning with the groundbreaking work of the Mackinnon group on the first K+ channel structure and subsequent work on both K+-selective and nonselective cation channels. These studies offer a wealth of direct insight into the structural details under- lying their selectivity properties (Doyle et al., 1998; Zhou et al., 2001; Shi et al., 2006; Valiyaveetil et al., 2006; Alam and Jiang, 2009b; Ye et al., 2010). With the focus on channel selectivity, several recent structural studies on K+ channel gating and inactivation are not included in this discussion. KcsA: the first view of a K+ channel In the absence of detailed structural information, mu

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