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Biophysical Journal 66: 345-354 (1994)
© 1994 the Biophysical Society

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S4 mutations alter gating currents of Shaker K channels.

E Perozo, L Santacruz-Toloza, E Stefani, F Bezanilla and D M Papazian

Department of Chemistry and Biochemistry, UCLA 90024-1751.

ABSTRACT

Activation of voltage-dependent channels involves charge-moving conformational changes of the voltage sensor that can be detected as gating currents. In Shaker K channels, the S4 sequence comprises at least part of the voltage sensor. We have measured gating currents in three S4 mutants: R368Q, R377K, and R371Q. R368Q enhances the separation of two components of charge movement and greatly reduces the valence of one component. R377K partially uncouples charge movement from channel opening. In contrast, the gating currents of R371Q resemble those of the control. Two other S4 mutations, R377Q and K374Q, make proteins that are not properly processed and transported to the cell surface and thereby eliminate the gating current. To explain the effects of R368Q, we hypothesize that R368 is part of a salt bridge that is broken early in activation. Subsequently, the S4 segment undergoes a conformational change, and, after a final, relatively voltage-independent step, the channel opens.




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Y. Sato, M. Sakaguchi, S. Goshima, T. Nakamura, and N. Uozumi
Molecular Dissection of the Contribution of Negatively and Positively Charged Residues in S2, S3, and S4 to the Final Membrane Topology of the Voltage Sensor in the K+ Channel, KAT1
J. Biol. Chem., April 11, 2003; 278(15): 13227 - 13234.
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Copyright © 1994 by the Biophysical Society.