3k6n

Publication Abstract from PubMed

Strong voltage sensitivity of inward-rectifier K(+) (Kir) channels has been hypothesized to arise primarily from an intracellular blocker displacing up to five K(+) ions from the wide, intracellular part of the ion conduction pore outwardly across the narrow ion-selectivity filter. The validity of this hypothesis depends on two assumptions: (i) that five ion sites are located intracellular to the filter and (ii) that the blocker can force essentially unidirectional K(+) movement in a pore region generally wider than the combined dimensions of the blocker plus a K(+) ion. Here we present a crystal structure of the cytoplasmic portion of a Kir channel with five ions bound and demonstrate that a constriction near the intracellular end of the pore, acting as a gasket, prevents K(+) ions from bypassing the blocker. This heretofore unrecognized 'gasket' ensures that the blocker can effectively displace K(+) ions across the selectivity filter to generate exceedingly strong voltage sensitivity.

Physical determinants of strong voltage sensitivity of K(+) channel block.,Xu Y, Shin HG, Szep S, Lu Z Nat Struct Mol Biol. 2009 Dec;16(12):1252-8. Epub 2009 Nov 15. PMID:19915587^[1]

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