The concerted contribution of the S4-S5 linker and the S6 segment to the modulation of a Kv channel by 1-alkanols.
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.
Bhattacharji
Aditya
A
Department of Pathology, Anatomy and Cell Biology, Jefferson Medical College of Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA 19107, USA.
Kaplan
Benjamin
B
Harris
Thanawath
T
Qu
Xiaoguang
X
Germann
Markus W
MW
Covarrubias
Manuel
M
D020001:1-Butanol / Q000494:pharmacology*; D000595:Amino Acid Sequence; D000818:Animals; D002942:Circular Dichroism; D019281:Dimerization; D015640:Ion Channel Gating / Q000187:drug effects* / Q000502:physiology; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D019906:Nuclear Magnetic Resonance, Biomolecular; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D051381:Rats; D051670:Shaw Potassium Channels / Q000737:chemistry* / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013816:Thermodynamics; D014981:Xenopus
D051670:Shaw Potassium Channels; D020001:1-Butanol