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Please use this identifier to cite or link to this item: http://dspace.utalca.cl/handle/1950/9128

Title: The pH sensor of the plant K+-uptake channel KAT1 is built from a sensory cloud rather than from single key amino acids
Authors: Gonzalez, W.
Riedelsberger, J.
Morales-Navarro, S.E.
Caballero, J.
Alzate-Morales, J.H.
Gonzalez-Nilo, F.D.
Dreyer, I.
Keywords: Arabidopsis thaliana
channel protein structure
channel protein-proton interaction
pH regulation
potassium chanel
Issue Date: Feb-2012
Citation: BIOCHEMICAL JOURNAL Volume: 442 Pages: 57-63
Abstract: The uptake of potassium ions (K+) accompanied by an acidification of the apoplasm is a prerequisite for stomatal opening. The acidification (approximately 2-2.5 pH units) is perceived by voltage-gated inward potassium channels (K-in) that then can open their pores with lower energy cost. The sensory units for extracellular pH in stomatal K-in channels are proposed to be histidines exposed to the apoplasm. However, in the Arabidopsis thaliana stomatal K-in channel KAT1, mutations in the unique histidine exposed to the solvent (His(267)) do not affect the pH dependency. We demonstrate in the present study that His(267) of the KAT1 channel cannot sense pH changes since the neighbouring residue Phe(266) shifts its pK(a) to undetectable values through a cation-pi interaction. Instead, we show that Glu(240) placed in the extracellular loop between transmembrane segments S5 and S6 is involved in the extracellular acid activation mechanism. Based on structural models we propose that this region may serve as a molecular link between the pH- and the voltage-sensor. Like Glu(240), several other titratable residues could contribute to the pH-sensor of KAT1, interact with each other and even connect such residues far away from the voltage-sensor with the gating machinery of the channel.
Description: Gonzalez, W (reprint author), Univ Talca, Ctr Bioinformat & Simulac Mol, 2 Norte 685, Talca 3465548, Chile.
URI: http://dspace.utalca.cl/handle/1950/9128
ISSN: 0264-6021
Appears in Collections:Artículos en publicaciones ISI - Universidad de Talca

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