TY  - JOUR
A1  - Garcia-Mata, Carlos
A1  - Wang, Jianwen
A1  - Gajdanowicz, Pawel
A1  - Gonzalez, Wendy
A1  - Hills, Adrian
A1  - Donald, Naomi
A1  - Riedelsberger, Janin
A1  - Amtmann, Anna
A1  - Dreyer, Ingo
A1  - Blatt, Michael R.
T1  - A minimal cysteine motif required to activate the SKOR K+ channel of Arabidopsis by the reactive oxygen species H2O2
N2  - Reactive oxygen species (ROS) are essential for development and stress signaling in plants. They contribute to plant defense against pathogens, regulate stomatal transpiration, and influence nutrient uptake and partitioning. Although both Ca2+ and K+ channels of plants are known to be affected, virtually nothing is known of the targets for ROS at a molecular level. Here we report that a single cysteine (Cys) residue within the Kv-like SKOR K+ channel of Arabidopsis thaliana is essential for channel sensitivity to the ROS H2O2. We show that H2O2 rapidly enhanced current amplitude and activation kinetics of heterologously expressed SKOR, and the effects were reversed by the reducing agent dithiothreitol (DTT). Both H2O2 and DTT were active at the outer face of the membrane and current enhancement was strongly dependent on membrane depolarization, consistent with a H2O2-sensitive site on the SKOR protein that is exposed to the outside when the channel is in the open conformation. Cys substitutions identified a single residue, Cys(168) located within the S3 alpha-helix of the voltage sensor complex, to be essential for sensitivity to H2O2. The same Cys residue was a primary determinant for current block by covalent Cys S-methioylation with aqueous methanethiosulfonates. These, and additional data identify Cys168 as a critical target for H2O2, and implicate ROS-mediated control of the K+ channel in regulating mineral nutrient partitioning within the plant.
Y1  - 2010
UR  - http://www.jbc.org/
U6  - https://doi.org/10.1074/jbc.M110.141176
SN  - 0021-9258
ER  - 
TY  - JOUR
A1  - Lefoulon, Cecile
A1  - Karnik, Rucha
A1  - Honsbein, Annegret
A1  - Gutla, Paul Vijay
A1  - Grefen, Christopher
A1  - Riedelsberger, Janin
A1  - Poblete, Tomas
A1  - Dreyer, Ingo
A1  - Gonzalez, Wendy
A1  - Blatt, Michael R.
T1  - Voltage-sensor transitions of the inward-rectifying K+ channel KAT1 indicate a latching mechanism biased by hydration within the voltage sensor
JF  - Plant physiology : an international journal devoted to physiology, biochemistry, cellular and molecular biology, biophysics and environmental biology of plants
N2  - The Kv-like (potassium voltage-dependent) K+ channels at the plasma membrane, including the inward-rectifying KAT1 K+ channel of Arabidopsis (Arabidopsis thaliana), 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-directed mutagenesis to explore residues that are thought to form two electrostatic countercharge centers on either side of a conserved phenylalanine (Phe) residue within the S2 and S3 alpha-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 countercharge centers favored the open channel. Modeling of the macroscopic current kinetics also highlighted a substantial difference between the two sets of mutations. We interpret these findings in the 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.
Y1  - 2014
U6  - https://doi.org/10.1104/pp.114.244319
SN  - 0032-0889
SN  - 1532-2548
VL  - 166
IS  - 2
SP  - 960
EP  - U776
PB  - American Society of Plant Physiologists
CY  - Rockville
ER  -