Abstract
The effects of intracellular Na(+) were studied on K(+) and Rb(+) currents through single KcsA channels. At low voltage, Na(+) produces voltage-dependent block, which becomes relieved at high voltage by a "punchthrough" mechanism representing Na(+) escaping from its blocking site through the selectivity filter. The Na(+) blocking site is located in the wide, hydrated vestibule, and it displays unexpected selectivity for K(+) and Rb(+) against Na(+). The voltage dependence of Na(+) block reflects coordinated movements of the blocker with permeant ions in the selectivity filter.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Bacterial Proteins / chemistry
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Bacterial Proteins / metabolism*
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Cell Membrane Permeability / drug effects
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Cell Membrane Permeability / physiology*
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Ion Channel Gating / drug effects
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Ion Channel Gating / physiology
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Lipid Bilayers / metabolism
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Membrane Potentials / drug effects
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Membrane Potentials / physiology
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Membranes, Artificial*
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Potassium Channels / chemistry
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Potassium Channels / metabolism*
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Sodium / metabolism*
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Sodium / pharmacology
Substances
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Bacterial Proteins
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Lipid Bilayers
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Membranes, Artificial
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Potassium Channels
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prokaryotic potassium channel
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Sodium