title: Voltage-sensor transitions of the inward-rectifying K+ channel KAT1 indicate a latching mechanism biased by hydration within the voltage sensor.
abstract: 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 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 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.
authors.affiliation: Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.).
authors.forename: Cécile
authors.initials: C
authors.lastname: Lefoulon
authors.affiliation: Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.).
authors.forename: Rucha
authors.initials: R
authors.lastname: Karnik
authors.affiliation: Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.).
authors.forename: Annegret
authors.initials: A
authors.lastname: Honsbein
authors.affiliation: Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.).
authors.forename: Paul Vijay
authors.initials: PV
authors.lastname: Gutla
authors.affiliation: Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.).
authors.forename: Christopher
authors.initials: C
authors.lastname: Grefen
authors.affiliation: Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.).
authors.forename: Janin
authors.initials: J
authors.lastname: Riedelsberger
authors.affiliation: Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.).
authors.forename: Tomás
authors.initials: T
authors.lastname: Poblete
authors.affiliation: Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.).
authors.forename: Ingo
authors.initials: I
authors.lastname: Dreyer
authors.affiliation: Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.) wgonzalez@utalca.cl michael.blatt@glasgow.ac.uk.
authors.forename: Wendy
authors.initials: W
authors.lastname: Gonzalez
authors.affiliation: Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.) wgonzalez@utalca.cl michael.blatt@glasgow.ac.uk.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Blatt
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D015640:Ion Channel Gating; D008969:Molecular Sequence Data; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014867:Water / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C501210:KAT1 protein, Arabidopsis; D024661:Potassium Channels, Inwardly Rectifying; D014867:Water