[The effect of thylakoid lipids on cytochrome bf complex activity]

The effects of glycerolipids from thylakoid membranes on the electron transport and proton-translocating activities of the cytochrome bf complex from spinach have been studied. When the cytochrome bf complex was mixed with the lipids from the wild type of Synechocystis PCC6803 containing mono-, di- and triunsaturated lipid molecules, the activity of the electron transport was stimulated by DGDG and PG, but not by MGDG and SQDG. Essentially the same effect, though less significant, was observed with lipids from a desaturation mutant containing only monounsaturated lipid molecules. At the same time, none of these lipids activated the proton translocation function. The highest proton-translocating activities were observed in mixtures of these lipids. No activity of proton translocation was found, however, when the cytochrome bf complex was mixed with the mutant strain lipids. It may thus be concluded that polyunsaturated lipid molecules are obligately required for the activity of proton translocation, while they have a negligible stimulating effect on the oxidoreductase activity.