Distinct roles of the last transmembrane domain in controlling Arabidopsis K+ channel activity.
The family of voltage-gated potassium channels in plants presumably evolved from a common ancestor and includes both inward-rectifying (K(in)) channels that allow plant cells to accumulate K(+) and outward-rectifying (K(out)) channels that mediate K(+) efflux. Despite their close structural similarities, the activity of K(in) channels is largely independent of K(+) and depends only on the transmembrane voltage, whereas that of K(out) channels responds to the membrane voltage and the prevailing extracellular K(+) concentration. Gating of potassium channels is achieved by structural rearrangements within the last transmembrane domain (S6). Here we investigated the functional equivalence of the S6 helices of the K(in) channel KAT1 and the K(out) channel SKOR by domain-swapping and site-directed mutagenesis. Channel mutants and chimeras were analyzed after expression in Xenopus oocytes. We identified two discrete regions that influence gating differently in both channels, demonstrating a lack of functional complementarity between KAT1 and SKOR. Our findings are supported by molecular models of KAT1 and SKOR in the open and closed states. The role of the S6 segment in gating evolved differently during specialization of the two channel subclasses, posing an obstacle for the transfer of the K(+)-sensor from K(out) to K(in) channels.
Gajdanowicz
Pawel
P
Universität Potsdam, Institut für Biochemie und Biologie, Heisenberg-Gruppe Biophysik und Molekulare Pflanzenbiologie, 14476 Potsdam/Golm, Germany.
Garcia-Mata
Carlos
C
Laboratory of Plant Physiology and Biophysics, IBLS Plant Sciences, Bower Building, University of Glasgow, Glasgow G12 8QQ, UK.|Laboratorio de Fisiologia Molecular e Integrativa, Institutos de Investigaciones Biologicas, Universidad Nacional de Mar del Plata, 7600 Mar del Plata, Buenos Aires, Argentina.
Gonzalez
Wendy
W
Universität Potsdam, Institut für Biochemie und Biologie, Heisenberg-Gruppe Biophysik und Molekulare Pflanzenbiologie, 14476 Potsdam/Golm, Germany.|Centro de Bioinformática y Simulación Molecular, Universidad de Talca, Casilla 721, Talca, Chile.
Morales-Navarro
Samuel Elías
SE
Centro de Bioinformática y Simulación Molecular, Universidad de Talca, Casilla 721, Talca, Chile.
Sharma
Tripti
T
Universität Potsdam, Institut für Biochemie und Biologie, Heisenberg-Gruppe Biophysik und Molekulare Pflanzenbiologie, 14476 Potsdam/Golm, Germany.|Max-Planck Institute of Molecular Plant Physiology, 14476 Potsdam/Golm, Germany.
González-Nilo
Fernando Danilo
FD
Centro de Bioinformática y Simulación Molecular, Universidad de Talca, Casilla 721, Talca, Chile.
Gutowicz
Jan
J
Department of Physical Chemistry of Microorganisms, Institute of Genetics and Microbiology, University of Wrocław, 51148 Wrocław, Poland.
Mueller-Roeber
Bernd
B
Max-Planck Institute of Molecular Plant Physiology, 14476 Potsdam/Golm, Germany.|Universität Potsdam, Institut für Biochemie und Biologie, Abteilung Molekularbiologie, 14476 Potsdam/Golm, Germany.
Blatt
Michael R
MR
Laboratory of Plant Physiology and Biophysics, IBLS Plant Sciences, Bower Building, University of Glasgow, Glasgow G12 8QQ, UK.
Dreyer
Ingo
I
Universität Potsdam, Institut für Biochemie und Biologie, Heisenberg-Gruppe Biophysik und Molekulare Pflanzenbiologie, 14476 Potsdam/Golm, Germany.
D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000737:chemistry / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D003198:Computer Simulation; D008954:Models, Biological; D008958:Models, Molecular; D008961:Models, Structural; D009154:Mutation; D009865:Oocytes; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry* / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated / Q000737:chemistry* / Q000378:metabolism*; D016415:Sequence Alignment; D051637:Shaker Superfamily of Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014981:Xenopus
D029681:Arabidopsis Proteins; C501210:KAT1 protein, Arabidopsis; D024661:Potassium Channels, Inwardly Rectifying; D024642:Potassium Channels, Voltage-Gated; C114544:SKOR protein, Arabidopsis; D051637:Shaker Superfamily of Potassium Channels