Allostery is a fundamental element during channel gating in response to an appropriate stimulus by which events occurring at one site are transmitted to distal sites to regulate activity. To address how binding of the...
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Allostery is a fundamental element during channel gating in response to an appropriate stimulus by which events occurring at one site are transmitted to distal sites to regulate activity. To address how binding of the first Caion at one of the eight chemically identical subunits facilitates the other Ca-binding events in Mth K, a Ca-gated K+channel containing a conserved ligand-binding RCK domain, we analysed a large collection of Mth K structures and performed the corresponding thermodynamic and electrophysiological measurements. These structural and functional studies led us to conclude that the conformations of the Ca-binding sites alternate between two quaternary states and exhibit significant differences in Caaffinity. We further propose an allosteric model of the Mth K-gating mechanism by which a cascade of structural events connect the initial Ca-binding to the final changes of the ring structure that open the ion-conduction pore. This mechanical model reveals the exquisite design that achieves the allosteric gating and could be of general relevance for the action of other ligand-gated ion channels containing the RCK domain.
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