Gating of voltage-gated Kϩ channels (K v channels) depends on the electromechanical coupling between the voltage sensor and activation gate. The main activation gate of K v 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 ϩ channel. In the S4 -S5 linker, we found a direct energetic correlation between ␣-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 K v 3.4 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 K v channel tetramer. Consistent with the critical contribution of the Shaw2 S4 -S5 linker, the equivalent PVAV mutation in certain mammalian K v 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 ϩ channel by an interaction with its activation gate.The molecular basis of alcohol and general anesthetic action on neuronal ion channels has been investigated intensely in the past decade (Peoples et al

The modulation of the Drosophila Shaw2 Kv channel by 1-alkanols and inhaled anesthetics is correlated with the involvement of the S4–S5 linker and C-terminus of S6, and consistent with stabilization of the channel’s closed state. Structural analysis of peptides from S4–S5 (L45) and S6 (S6c), by nuclear magnetic resonance and circular dichroism spectroscopy supports that an α-helical conformation was adopted by L45, while S6c was only in an unstable/dynamic partially folded α-helix in dodecylphosphocholine micelles. Solvent accessibility and paramagnetic probing of L45 revealed that L45 lies parallel to the surface of micelles with charged and polar residues pointing towards the solution while hydrophobic residues are buried inside the micelles. Chemical shift perturbation introduced by 1-butanol on residues Gln320, Thr321, Phe322 and Arg323 of L45, as well as Thr423 and Gln424 of S6c indicates possible anesthetic binding sites on these two important components in the channel activation apparatus. Diffusion measurements confirmed the association of L45, S6c and 1-butanol with micelles which suggests the capability of 1-butanol to influence a possible interaction of L45 and S6c in the micelle environment.