Reducing S3-S4 Linker Length in Shaker K+ Channels Stabilizes the Relaxed State

ORCiD

Carlos A. Villalba-Galea: 0000-0002-6489-4651

Document Type

Poster

Conference Title/Conference Publication

Biophysical Journal

Organization

Biophysical Society 56th Annual Meeting

Location

San Diego, CA

Conference Dates

February 25-29, 2012

Date of Presentation

2-25-2012

ISSN

0006-3495

Volume

102

Issue

3, Supplement 1

DOI

10.1016/j.bpj.2011.11.2897

First Page

530a

Abstract

The voltage sensing domain (VSD) of voltage-gated channels contains four transmembrane segments (S1 through S4), where the S4 segment is the main voltage sensor. It has been shown that upon prolonged depolarization the VSD enters a third conformational state, the relaxed state, resulting in a dramatic slowing of gating current kinetics upon a repolarization. The length of the linker between the third and fourth transmembrane domains (the S3-S4 linker) is highly variable between different voltage-gated potassium channels. Here we investigated whether the S3-S4 linker length affects the relaxation transition. We generated mutant clones of the Shaker K+ (ShK) IR-H4, W434F background (wild type) with S3-S4 linkers progressively shortened by, typically, three residues. We found that upon prolonged depolarization, the kinetics of repolarizing gating currents going from the relaxed state to the resting state slow down with a linear correlation with the length of the S3-S4 linker (R2>0.9). In addition, the entry to the relaxed state for short linker constructs was generally faster than that for wild type. These results show that shortening the S3-S4 linker favors the relaxed conformation. In addition, we recorded gating currents from oocytes expressing two fragments of ShK, one from the N terminus through part of the S3-S4 linker, and the other comprised of the remainder of the S3-S4 linker to the C terminus. This “split linker” construct and our short linker constructs suggest that shorter S3-S4 linkers impose greater constraints on the voltage sensor, stabilizing the relaxed state. Supported by NIH-GM030376.

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