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Publication Abstract from PubMed

K+ channels are highly selective for K+ over Na+. Here we present several crystal structures of the MthK K+ channel pore at up to 1.45-A resolution. The MthK selectivity filter maintains a conductive conformation even in the absence of K+, allowing the channel to conduct Na+. The high-resolution structures, along with single-channel recordings, allow for an accurate analysis of how K+ competes with Na+ in a conductive selectivity filter. At high K+ concentrations, two K+ ions equivalently occupy the four sites in the selectivity filter, whereas at low K+/high Na+ concentrations, a single K+ ion remains bound in the selectivity filter, preferably at site 1 or site 3. This single K+ binding at low concentration effectively blocks the permeation of Na+, providing a structural basis for the anomalous mole-fraction effect, a key property of multi-ion pores.

Novel insights into K+ selectivity from high-resolution structures of an open K+ channel pore.,Ye S, Li Y, Jiang Y Nat Struct Mol Biol. 2010 Aug;17(8):1019-23. Epub 2010 Aug 1. PMID:20676101^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.