Hurt, E.C., Intstitut für Botanik, Universität Regensburg, 8400 Regensburg, Germany
Hauska, G., Intstitut für Botanik, Universität Regensburg, 8400 Regensburg, Germany
Shahak, Y., Biochemistry Department, Wseizmann Institute of Science, Rehovot, 76100, Israel

When the cytochrome b6/f complex from chloroplasts is incorporated into liposomes, reduction of external plastocyanin by plastoquinol is stimulated under uncoupling conditions. An extra H+/e- is ejected from the vesicles during the reaction, in addition to the scalar proton liberated from plastoquinol. This is stimulated by valinomycin/K+ and abolished under uncoupling conditions. Furthermore, the formation of a membrane potential during the reaction, negative inside the vesicles, is observed with the help of carbocyanine dyes. We conclude that the cytochrome b6/f complex, like the cytochrome bc1 from mitochondria, functions as an electrogenic proton translocator. © 1982.