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  • Title: Conformational dynamics of the KcsA potassium channel governs gating properties.
    Author: Baker KA, Tzitzilonis C, Kwiatkowski W, Choe S, Riek R.
    Journal: Nat Struct Mol Biol; 2007 Nov; 14(11):1089-95. PubMed ID: 17922011.
    Abstract:
    K+ channels conduct and regulate K+ flux across the cell membrane. Several crystal structures and biophysical studies of tetrameric ion channels have revealed many of the structural details of ion selectivity and gating. A narrow pore lined with four arrays of carbonyl groups is responsible for ion selectivity, whereas a conformational change of the four inner transmembrane helices (TM2) is involved in gating. We used NMR to examine full-length KcsA, a prototypical K+ channel, in its open, closed and intermediate states. These studies reveal that at least two conformational states exist both in the selectivity filter and near the C-terminal ends of the TM2 helices. In the ion-conducting open state, we observed rapid structural exchange between two conformations of the filter, presumably of low and high K+ affinity, respectively. Such measurements of millisecond-timescale dynamics reveal the basis for simultaneous ion selection and gating.
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