Voltage-sensor transitions of the inward-rectifying K+ channel KAT1 indicate a latching mechanism biased by hydration within the voltage sensor

Lefoulon, C., Karnik, R., Honsbein, A., Gutla, P. V., Grefen, C., Riedelsberger, J., Poblete, T., Dreyer, I., Gonzalez, W. and Blatt, M. R. (2014) Voltage-sensor transitions of the inward-rectifying K+ channel KAT1 indicate a latching mechanism biased by hydration within the voltage sensor. Plant Physiology, 166(2), pp. 960-975. (doi:10.1104/pp.114.244319) (PMID:25185120)

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Abstract

The Kv-like K+ channels at the plasma membrane, including the inward-rectifying KAT1 K+ channel of Arabidopsis, are important targets for manipulating K+ homeostasis in plants. Gating modification, especially, has been identified as a promising means by which to engineer plants with improved characteristics in mineral and water use. Understanding plant K+ channel gating poses several challenges, despite many similarities to that of mammalian Kv and Shaker channel models. We have used site-mutagenesis to explore residues that are thought to form two electrostatic counter-charge centers either side of a conserved Phe residue within the S2 and S3 α-helices of the voltage sensor domain (VSD) of Kv channels. Consistent with molecular dynamic simulations of KAT1, we show that the voltage dependence of the channel gate is highly sensitive to manipulations affecting these residues. Mutations of the central Phe residue favored the closed KAT1 channel, whereas mutations affecting the counter-charge centers favored the open channel. Modelling of the macroscopic current kinetics also highlighted a substantial difference between the two sets of mutations. We interpret these findings in context of the effects on hydration of amino-acid residues within the VSD and with an inherent bias of the VSD, when hydrated around a central Phe residue, to the closed state of the channel.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Blatt, Professor Michael and Grefen, Dr Christopher and Karnik, Dr Rucha and Honsbein, Dr Annegret and Gutla, Mr Paul and Lefoulon, Dr Cecile
Authors: Lefoulon, C., Karnik, R., Honsbein, A., Gutla, P. V., Grefen, C., Riedelsberger, J., Poblete, T., Dreyer, I., Gonzalez, W., and Blatt, M. R.
College/School:College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
Journal Name:Plant Physiology
Publisher:American Society of Plant Biologists
ISSN:0032-0889
ISSN (Online):1532-2548
Copyright Holders:Copyright © 2014 The Authors
First Published:First published in Plant Physiology 166(2):960-975
Publisher Policy:Reproduced under a Creative Commons License

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