Distinct roles of the last transmembrane domain in controlling Arabidopsis K+ channel activity

PAWEL GAJDANOWICZ; CARLOS GARCIA-MATA; WENDY GONZALEZ; SAMUEL ELÍAS MORALES-NAVARRO; TRIPTI SHARMA; FERNANDO DANILO GONZÁLEZ-NILO; JAN GUTOWICZ; BERND MUELLER-ROEBE; MICHAEL R. BLATT; INGO DREYER

NEW PHYTOLOGIST

WILEY-BLACKWELL PUBLISHING, INC

Año: 2009 vol. 182 p. 380 - 391

0028-646X

• 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.