Evaluation of different mechanistic proposals for water oxidation in photosynthesis on the basis of Mn4OxCa structures for the catalytic site and spectroscopic data

摘要: Recent progress in EPR and EXAFS spectroscopy, quantum mechanical calculations X-ray crystallography led to a tremendous improvement our picture of the catalytic site water oxidation photosystem II. It is now likely that four Mn ions are grouped 3 + 1 fashion with three short Mn–Mn distances about 2.7 A one long distance 3.3 A. In addition, Ca has been firmly localized close centers, an average 3.4 angle Mn–Ca vectors membrane normal (≤23°). The recent crystal structure Ferreira et al. (Science, 2004, 303, 1831–1838) suggests Mn3 unit form distorted cubane like structure. fourth ‘dangling’ from this either via μ4-oxo bridge or mono μ-oxo bridge. However, precise bridging situation still need be worked out. On structural basis available spectroscopic data two possible mechanisms for photosynthetic discussed order highlight questions solved full understanding fascinating reaction.