The Journal of General Physiology
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Published online
doi:10.1085/jgp.200810082
The Journal of General Physiology, Vol. 133, No. 5, 467-483
The Rockefeller University Press, 0022-1295 $30.00
© Gagnon et al.
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ARTICLE

 A single charged voltage sensor is capable of gating the Shaker K+ channel

Dominique G. Gagnon and Francisco Bezanilla

Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637

Correspondence to Francisco Bezanilla: fbezanilla{at}uchicago.edu

We sought to determine the contribution of an individual voltage sensor to Shaker's function. Concatenated heterotetramers of Shaker zH4 {Delta}(6–46) wild type (wt) in combination with a neutral S4 segment Shaker mutant (mut) with stoichiometries 2wt/2mut and 1wt/3mut were studied and compared with the 4wt concatenated homotetramer. A single charged voltage sensor is sufficient to open Shaker conductance with reduced delay (<1 ms) and at more hyperpolarized voltages compared with 4wt. In addition, the wt-like slow inactivation of 1wt/3mut was almost completely eliminated by mutations T449V-I470C in its single wt subunit, indicating that the subunits bearing a neutral S4 were unable to trigger slow inactivation. Our results strongly suggest that a neutral S4 segment of Shaker's subunit is voltage insensitive and its voltage sensor is in the activated position (i.e., ready for pore opening), and provide experimental support to the proposed model of independent voltage sensors with a final, almost voltage-independent concerted step.

Abbreviations used in this paper: HP, holding potential; ILT, V369I+I372L+S376T mutant; IR, non-inactivating; MS, methanesulfonic acid; mut, mutant; wt, wild-type.

© 2009 Gagnon and Bezanilla
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