pH control of the plant outwardly-rectifying potassium channel SKOR

SKOR, an Arabidopsis depolarisation-activated K+-selective channel, was exp ressed in Xenopus oocytes, and external and internal pH effects were analys ed. Internal pH was manipulated by injections of alkaline or acidic solutio ns or by acid load from acetate-containing medium. An internal pH decrease from 7.4 to 7.2 induced a strong (ca. 80%) voltage-independent decrease of the macroscopic SKOR current, the macroscopic gating parameters and the sin gle channel conductance remained unchanged. An external acidification from 7.4 to 6.4 had similar effects. It is proposed that pH changes regulate the number of channels available for activation. Sensitivity of SKOR activity to pH in the physiological range suggests that internal and external pH pla y a role in the regulation of K+ secretion into the xylem sap. (C) 2000 Fed eration of European Biochemical Societies.