The Cavity and Pore Helices in the KcsA K+ Channel: Electrostatic Stabilization of Monovalent Cations

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Science  02 Jul 1999:
Vol. 285, Issue 5424, pp. 100-102
DOI: 10.1126/science.285.5424.100

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The electrostatic influence of the central cavity and pore alpha helices in the potassium ion channel from Streptomyces lividans (KcsA K+ channel) was analyzed by solving the finite difference Poisson equation. The cavity and helices overcome the destabilizing influence of the membrane and stabilize a cation at the membrane center. The electrostatic effect of the pore helices is large compared to that described for water-soluble proteins because of the low dielectric membrane environment. The combined contributions of the ion self-energy and the helix electrostatic field give rise to selectivity for monovalent cations in the water-filled cavity. Thus, the K+ channel uses simple electrostatic principles to solve the fundamental problem of ion destabilization by the cell membrane lipid bilayer.

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