1k4d
From Proteopedia
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Potassium Channel KcsA-Fab complex in low concentration of K+
Overview
Ion transport proteins must remove an ion's hydration shell to coordinate, the ion selectively on the basis of its size and charge. To discover how, the K+ channel solves this fundamental aspect of ion conduction, we solved, the structure of the KcsA K+ channel in complex with a monoclonal Fab, antibody fragment at 2.0 A resolution. Here we show how the K+ channel, displaces water molecules around an ion at its extracellular entryway, and, how it holds a K+ ion in a square antiprism of water molecules in a cavity, near its intracellular entryway. Carbonyl oxygen atoms within the, selectivity filter form a very similar square antiprism around each K+, binding site, as if to mimic the waters of hydration. The selectivity, filter changes its ion coordination structure in low K+ solutions. This, structural change is crucial to the operation of the selectivity filter in, the cellular context, where the K+ ion concentration near the selectivity, filter varies in response to channel gating.
About this Structure
1K4D is a Single protein structure of sequence from Mus musculus and Streptomyces lividans with K, NA, DGA and F09 as ligands. Full crystallographic information is available from OCA.
Reference
Chemistry of ion coordination and hydration revealed by a K+ channel-Fab complex at 2.0 A resolution., Zhou Y, Morais-Cabral JH, Kaufman A, MacKinnon R, Nature. 2001 Nov 1;414(6859):43-8. PMID:11689936
Page seeded by OCA on Sun Nov 18 09:34:24 2007
