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

1999; American Association for the Advancement of Science; Volume: 285; Issue: 5424 Linguagem: Inglês

10.1126/science.285.5424.100

1095-9203

Benoı̂t Roux, Roderick MacKinnon,

Molecular Sensors and Ion Detection

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.