Abstract
Photosystem II (PSII) is a membrane protein complex consisting of at least 14 membrane-spanning subunits and 3 extrinsic proteins with a total molecular mass of 320 kDa for a monomer. In order to understand the molecular mechanisms taking place in the PSII complex, it is essential to solve its 3-D structure. We report here the PSII crystal structure from a thermophilic cyanobacterium Thermosynechococcus. vulcanus at 3.7-angstrom resolution. We have assigned most regions of the large subunits of PSII including the 12 kDa protein which was not assigned previously. This provided much new information on the molecular interactions among these large subunits. We will show the environment around the Mn-cluster, and the possible ligands for it. In addition, the arrangement of pigments and other cofactors including two β-carotenes will be discussed in relation to their functional implications.
