Electrokinetics of Miniature K+ Channel: Open-State V Sensitivity and Inhibition by K+ Driving Force

Electrokinetics of Miniature K+ Channel: Open-State V Sensitivity and Inhibition by K+ Driving Force Kcv, isolated from a Chlorella virus, is the smallest known K+ channel. When Kcv is expressed in Xenopus oocytes and exposed to 50 mM [K+]o, its open-state current-voltage relationship (I-V) has the shape of a “tilted S” between −200 and +120 mV. Details of this shape depend on the conditioning voltage (V c) immediately before an I-V recording. Unexpectedly, the I-V relationships, recorded in different [K+]o, do intersect. These characteristics are numerically described here by fits of a kinetic model to the experimental data. In this model, the V c sensitivity of I-V is mainly assigned to an affinity increase of external K+ association at more positive voltages. The general, tilted-S shape as well as the unexpected intersections of the I-V relationships are kinetically described by a decrease of the cord conductance by the electrochemical driving force for K+ in either direction, like in fast V-dependent blocking by competing ions. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Electrokinetics of Miniature K+ Channel: Open-State V Sensitivity and Inhibition by K+ Driving Force

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Publisher
Springer-Verlag
Copyright
Copyright © 2007 by Springer Science+Business Media, LLC
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232-006-0024-3
Publisher site
See Article on Publisher Site

Abstract

Kcv, isolated from a Chlorella virus, is the smallest known K+ channel. When Kcv is expressed in Xenopus oocytes and exposed to 50 mM [K+]o, its open-state current-voltage relationship (I-V) has the shape of a “tilted S” between −200 and +120 mV. Details of this shape depend on the conditioning voltage (V c) immediately before an I-V recording. Unexpectedly, the I-V relationships, recorded in different [K+]o, do intersect. These characteristics are numerically described here by fits of a kinetic model to the experimental data. In this model, the V c sensitivity of I-V is mainly assigned to an affinity increase of external K+ association at more positive voltages. The general, tilted-S shape as well as the unexpected intersections of the I-V relationships are kinetically described by a decrease of the cord conductance by the electrochemical driving force for K+ in either direction, like in fast V-dependent blocking by competing ions.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Jun 13, 2007

References

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