Protein phosphorylation-induced State I-State II transitions are dependent on thylakoid membrane microviscosity.

ABSTRACT

Incorporation of cholesterol hemisuccinate into thylakoid membranes decreased the membrane fluidity as measured by polarized fluorescence from 1,6-diphenyl-1,3,5-hexatriene. Increasing membrane viscosity in this manner did not inhibit the thylakoid membrane protein kinase. In contrast the effects of the protein phosphorylation on State I-State II transitions, which were observed in untreated membranes, were abolished. This observation is interpreted as indicating that protein phosphorylation-induced energy transfer changes are sensitive to membrane viscosity because they might require a lateral migration of the light-harvesting complex serving Photosystem II from grana to stromal lamellae. Cation effects on room- and low-temperature fluorescence emission properties and membrane adhesion were not abolished in these cholesterol hemisuccinate-treated membranes.