1k4d
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Potassium Channel KcsA-Fab complex in low concentration of K+
OverviewOverview
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 StructureAbout this Structure
1K4D is a Single protein structure of sequence from Mus musculus and Streptomyces lividans with , , and as ligands. Full crystallographic information is available from OCA.
ReferenceReference
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
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