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|Title: ||The pH sensor of the plant K plus uptake channel KAT1 is built from a sensory cloud rather than from single key amino acids|
|Authors: ||Gonzalez, W.|
|Issue Date: ||Sep-2012 |
|Publisher: ||WILEY-BLACKWELL, 111 RIVER ST, HOBOKEN 07030-5774, NJ USA|
|Citation: ||FEBS JOURNAL Volume: 279 Special Issue: SI Supplement: 1 Pages: 455-455|
|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 (Kin) that then can
open their pores with lower energy cost. The sensory units for
extracellular pH in stomatal Kin channels are proposed to be histidines
exposed to the apoplasm. However, in the Arabidopsis
thaliana stomatal Kin channel KAT1, mutations in the unique
histidine exposed to the solvent (His267) do not affect the pH
dependency. We demonstrate in the present study that His267 of
the KAT1 channel cannot sense pH changes since the neighbouring
residue Phe266 shifts its pKa to undetectable values through
a cation–p interaction. Instead, we show that Glu240 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 Glu240, 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.|
|Appears in Collections:||Artículos en publicaciones ISI - Universidad de Talca|
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