Title

S3-S4 linker length modulates the relaxed state of a voltage-gated potassium channel

ORCiD

0000-0002-6489-4651

Document Type

Article

Publication Title

Biophysical Journal

ISSN

1542-0086

Volume

105

Issue

10

DOI

10.1016/j.bpj.2013.09.053

First Page

2312

Last Page

2322

Publication Date

11-19-2013

Abstract

Voltage-sensing domains (VSDs) are membrane protein modules found in ion channels and enzymes that are responsible for a large number of fundamental biological tasks, such as neuronal electrical activity. The VSDs switch from a resting to an active conformation upon membrane depolarization, altering the activity of the protein in response to voltage changes. Interestingly, numerous studies describe the existence of a third distinct state, called the relaxed state, also populated at positive potentials. Although some physiological roles for the relaxed state have been suggested, little is known about the molecular determinants responsible for the development and modulation of VSD relaxation. Several lines of evidence have suggested that the linker (S3-S4 linker) between the third (S3) and fourth (S4) transmembrane segments of the VSD alters the equilibrium between resting and active conformations. By measuring gating currents from the Shaker potassium channel, we demonstrate here that shortening the S3-S4 linker stabilizes the relaxed state, whereas lengthening the linker or splitting it and coinjecting two fragments of the channel have little effect. We propose that natural variations of the length of the S3-S4 linker in various VSD-containing proteins may produce differential VSD relaxation in vivo.