Abstract
The success of crystallization with PSII from thermophilic cyanobacteria has led to the structural analysis of PSII at a near-atomic level. What are the functions of PSII newly identified from its three-dimensional structure? We discuss the functions of PSII by incorporating the structural information yielded from both our group and other groups. Among them are the arrangement of chls in PSII-RC which showed that the distance between the two chl dimers in PSII-RC is longer than those in purple bacterial RC and PSI, but shorter than those between RC and accessory chls, indicating that PSII RC is a weakly coupled dimer. In addition, structure of the extrinsic 33 kDa protein showed some similarities with the Omp protein family, suggesting that this protein may function as a channel to transport small molecules. We will also discuss the characteristic structure of the Mn-cluster and its surrounding environment.
