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 (Kin) channels that allow plant cells to accumulate K+ and outward-rectifying (Kout) channels that mediate K+ efflux. Despite their close structural similarities, the activity of Kin channels is largely independent of K+ and depends only on the transmembrane voltage, whereas that of Kout 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 Kin channel KAT1 and the Kout 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 Kout to Kin channels.Fil: Gajdanowicz, Pawel. Universität Potsdam; AlemaniaFil: Garcia-Mata, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas. Laboratorio de Fisiología Molecular e Integrativa; Argentina. University of Glasgow; Reino UnidoFil: Gonzalez, Wendy. Universidad de Talca; Chile. Universität Potsdam; AlemaniaFil: Morales Navarro, Samuel Elías. Universidad de Talca; ChileFil: Sharma, Tripti. Max Planck Institute of Molecular Plant Physiology; Alemania. Universität Potsdam; AlemaniaFil: Gonzalez Nilo, Fernando Danilo. Universidad de Talca; ChileFil: Gutowicz, Jan. University of Wroclaw; PoloniaFil: Mueller Roeber, Bernd. Max Planck Institute of Molecular Plant Physiology; Alemania. Universität Potsdam; AlemaniaFil: Blatt, Michael R.. University of Glasgow; Reino UnidoFil: Dreyer, Ingo. Universität Potsdam; Alemani