抄録
Photosystem II (PSII) is a multi-subunit membrane protein complex. PSII performs a series of light-induced electron transfer reactions leading to the splitting of water and generation of molecular oxygen, the latter of which is essential for almost all life on the earth. The catalytic center is a Mn4CaO5-cluster, whose detailed structure has been successfully resolved in the 1.9 Å structure of PSII from Thermosynechococcus vulcanus. This structure also revealed the presence of nearly 2,800 water molecules, some of which are directly associated with the Mn4CaO5-cluster and thus may serve as the substrate water molecules for the oxygen-evolving reaction.