Abstract
Gating of voltage-gated K+ channels (Kv channels) depends on the electromechanical coupling between the voltage sensor and activation gate. The main activation gate of Kv channels involves the COOH-terminal section of the S6 segment (S6-b) and the S4-S5 linker at the intracellular mouth of the pore. In this study, we have expanded our earlier work to probe the concerted contribution of these regions to the putative amphipathic 1-alkanol site in the Shaw2 K+ channel. In the S4-S5 linker, we found a direct energetic correlation between α-helical propensity and the inhibition of the Shaw2 channel by 1-butanol. Spectroscopic structural analyses of the S4-S5 linker supported this correlation. Furthermore, the analysis of chimeric Shaw2 and Kv3.4 channels that exchanged their corresponding S4-S5 linkers showed that the potentiation induced by 1-butanol depends on the combination of a single mutation in the S6 PVPV motif (PVAV) and the presence of the Shaw2 S4-S5 linker. Then, using tandem-heterodimer subunits, we determined that this potentiation also depends on the number of S4-S5 linkers and PVAV mutations in the Kv channel tetramer. Consistent with the critical contribution of the Shaw2 S4-S5 linker, the equivalent PVAV mutation in certain mammalian Kv channels with divergent S4-S5 linkers conferred weak potentiation by 1-butanol. Overall, these results suggest that 1-alkanol action in Shaw2 channels depends on interactions involving the S4-S5 linker and the S6-b segment. Therefore, we propose that amphiphilic general anesthetic agents such as 1-alkanols may modulate gating of the Shaw2 K+ channel by an interaction with its activation gate.
Footnotes
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This work was supported by National Institutes of Health research grant R01-AA010615 (to M.C.).
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A.B. and B.K. contributed equally to this study.
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ABBREVIATIONS: Kv, voltage-gated K+ channel; 1-BuOH, 1-butanol; Gp-V, peak chord conductance-voltage; TFE, 2,2,2-trifluoroethanol; NOESY, nuclear Overhauser effect spectroscopy.
- Received May 1, 2006.
- Accepted August 3, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
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