Similarity between electron donor side reactions in the solubilized Photosystem II-LHC II supercomplex and Photosystem-II-containing membranes

The PS II-LHC II supercomplex is a novel type of oxygen evolving Photosyste m II (PS II) core particle that contains the light harvesting complex prote ins Lhcb1/2/4/5 in addition to the PS II reaction centre, oxygen evolving c omplex (OEC) and inner antennae [Hankamer et al. (1997) Eur J Biochem 243: 422-429]. The 33 and 23 kDa extrinsic proteins in these particles have been localised by image analysis of electron micrographs and averaging techniqu es [Boekema et al. (1998) Eur J Biochem 252: 268-276]. To assay the functio nality of the water splitting complex, we compared the single flash P680(+) reduction kinetics in these supercomplexes with those of PS II-rich granal stack membranes (BBYs). We found that the P680(+) reduction kinetics in PS II-LHC II supercomplexes were indistinguishable from those in BBYs. We als o examined a number of PS II core particles lacking the Lhcb components. Al l of these had different P680(+) reduction kinetics, which we attributed to partial loss of OEC function before and during the measurements.