Spectroscopic characterization of the Photosystem II chlorophyll-protein complexes

Abstract We investigated by polarized light spectroscopy the organization of the pigments in the Photosystem II (PS II) reaction center of Chlamydomonas reinhardtii using PS II particles and subparticles of varying photochemical activity, antenna size and polypeptide composition. We demonstrate that the amplitude of the pheophytin photoreduction varies in parallel with the presence of a transition arising from the pheophytin molecules. We show that the transitions arising from the photoactive pigments are absent in the chlorophyll-protein complexes III and IV (CPIII and CPIV), and that all the other transitions present in the PS II particles are conserved, suggesting that CPIII is more likely to act as an antenna, as is the case for CPIV, rather than to bind alone the primary reactants.