Structural Basis for Calcium and Magnesium Regulation of a Large Conductance Calcium-Activated Potas

来源 :The 9th Asian Biophysics Association Symposium (ABA2015)(第九届 | 被引量 : 0次 | 上传用户:sina
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Large-conductance Ca2+-and voltage-activated BK channels, composed of poreforming α subunits and auxiliary β subunits, play important roles in diverse physiological activities.The β1 is predominately expressed in smooth muscle cells, where it greatly enhances the Ca2+ sensitivity of BK channels for proper regulation of smooth muscle tone.However, structural basis underlying dynamic interaction between BK mSlo1 α and β1 remains elusive.Using macroscopic ionic current recordings in various Ca2+ and Mg2+ concentrations, we identified two binding sites on the cytosolic N-terminal of β1, namely the electrostatic enhancing (E) site (mSlo1(K392,R393)∶∶β1(E13,T14)), increasing the calcium sensitivity of BK channels, and the hydrophobic (H) site (mSlo1 (L906,L908)∶∶β1(L5,V6,M7)), passing the physical force from the Ca2+ bowl onto the E site and S6 C-linker.Dynamic binding of these sites affects the interaction between the cytosolic domain (CTD) and voltage sensing domain(VSD), leading to the reduction of Mg2+ sensitivity.A comprehensive structural model of the BK(mSlo1α/β1) complex was reconstructed based on these functional studies, which provides structural and mechanistic insights for understanding BK gating.
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