The concerted contribution of the S4-S5 linker and the S6 segment to the modulation of a Kv channel by 1-alkanols

Mol Pharmacol. 2006 Nov;70(5):1542-54. doi: 10.1124/mol.106.026187. Epub 2006 Aug 3.

Abstract

Gating of voltage-gated K(+) 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(+) channel. In the S4-S5 linker, we found a direct energetic correlation between alpha-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(+) channel by an interaction with its activation gate.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • 1-Butanol / pharmacology*
  • Amino Acid Sequence
  • Animals
  • Circular Dichroism
  • Dimerization
  • Ion Channel Gating / drug effects*
  • Ion Channel Gating / physiology
  • Kinetics
  • Molecular Sequence Data
  • Mutation / genetics
  • Nuclear Magnetic Resonance, Biomolecular
  • Protein Structure, Quaternary
  • Protein Structure, Secondary
  • Rats
  • Shaw Potassium Channels / chemistry*
  • Shaw Potassium Channels / metabolism*
  • Structure-Activity Relationship
  • Thermodynamics
  • Xenopus

Substances

  • Shaw Potassium Channels
  • 1-Butanol