2itd
From Proteopedia
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Potassium Channel KcsA-Fab complex in Barium Chloride
Overview
Thermodynamic measurements of ion binding to the Streptomyces lividans, K(+) channel were carried out using isothermal titration calorimetry, whereas atomic structures of ion-bound and ion-free conformations of the, channel were characterized by x-ray crystallography. Here we use these, assays to show that the ion radius dependence of selectivity stems from, the channel's recognition of ion size (i.e., volume) rather than charge, density. Ion size recognition is a function of the channel's ability to, adopt a very specific conductive structure with larger ions (K(+), Rb(+), Cs(+), and Ba(2+)) bound and not with smaller ions (Na(+), Mg(2+), and, Ca(2+)). The formation of the conductive structure involves selectivity, filter atoms that are in direct contact with bound ions as well as protein, atoms surrounding the selectivity filter up to a distance of 15 A from the, ions. We conclude that ion selectivity in a K(+) channel is a property of, size-matched ion binding sites created by the protein structure.
About this Structure
2ITD is a Single protein structure of sequence from Mus musculus and Streptomyces lividans with as ligand. Full crystallographic information is available from OCA.
Reference
Structural and thermodynamic properties of selective ion binding in a K+ channel., Lockless SW, Zhou M, MacKinnon R, PLoS Biol. 2007 May;5(5):e121. PMID:17472437
Page seeded by OCA on Wed Jan 23 15:16:28 2008
