Role of lipids in the organization and function of Photosystem II studied by homogeneous catalytic hydrogenation of thylakoid membranes in situ

Abstract

The effects of homogeneous catalytic hydrogenation on the organization and function of Photosystem II was investigated by fluorescence induction kinetic measurements with isolated chloroplasts. The results showed that saturation of the double bonds of fatty acyl constituents of membrane lipids had distinct effects on PS II. We found that progressive hydrogenation resulted in a gradual decrease of PS II electron transport with a concomitant increase of the initial fluorescence rise from F 0, the non-variable level, to F p1, the intermediate plateau level, indicating that an optimal saturation level of fatty acids of membrane lipids is important in maintaining the efficient electron transfer from Q − A to plastoquinone pool. In addition, the fluorescence induction kinetics of DCMU-poisoned chloroplasts showed that the proportion of PS II β in the membrane was increased by hydrogenation, suggesting that the saturation level of fatty acids may play an important role in regulating the association of the peripheral chlorophyll a b light-harvesting complex II (LHC II-peripheral) with PS II β, thus determining the PS II heterogeneity in PS II α and PS II β.