INDICATIONS FOR A DIMERIC ORGANIZATION OF THE ANTENNA-DEPLETED REACTION-CENTER CORE OF PHOTOSYSTEM-II IN THYLAKOIDS OF INTERMITTENT LIGHT-GROWN PEA-PLANTS

Presently there is a debate and contradictory results on the supramole cular structure of Photosystem II (PS II) in the thylakoid membranes o f cyanobacteria, green algae and higher plants that is related to the question whether PS IT exists as dimer or monomer in the different mem branes. PS II is composed of several subunits. The core complex, the s mallest entity that is able to split water, consists of the subunits D 1-D2, cyt b(559), CP43, CP47, and the 33 kDa protein. In vivo, this co re complex is connected to peripheral light harvesting complexes: in c yanobacteria to the phycobilisomes and in green algae and higher plant s to the Chl a/b binding protein, the LHC II. In in vitro experiments the supramolecular structure of the core complexes has been found to b e dimeric or monomeric depending on a variety of experimental factors.