S1-state model of the O2-evolving complex of photosystem II.
نویسندگان
چکیده
We introduce a quantum mechanics/molecular mechanics model of the oxygen-evolving complex of photosystem II in the S(1) Mn(4)(IV,III,IV,III) state, where Ca(2+) is bridged to manganese centers by the carboxylate moieties of D170 and A344 on the basis of the new X-ray diffraction (XRD) model recently reported at 1.9 Å resolution. The model is also consistent with high-resolution spectroscopic data, including polarized extended X-ray absorption fine structure data of oriented single crystals. Our results provide refined intermetallic distances within the Mn cluster and suggest that the XRD model most likely corresponds to a mixture of oxidation states, including species more reduced than those observed in the catalytic cycle of water splitting.
منابع مشابه
Alternative mechanisms for O2 release and O-O bond formation in the oxygen evolving complex of photosystem II.
In a previous detailed study of all the steps of water oxidation in photosystem II, it was surprisingly found that O2 release is as critical for the rate as O-O bond formation. A new mechanism for O2 release has now been found, which can be described as an opening followed by a closing of the interior of the oxygen evolving complex. A transition state for peroxide rotation forming a superoxide ...
متن کاملS0-State model of the oxygen-evolving complex of photosystem II.
The S0 → S1 transition of the oxygen-evolving complex (OEC) of photosystem II is one of the least understood steps in the Kok cycle of water splitting. We introduce a quantum mechanics/molecular mechanics (QM/MM) model of the S0 state that is consistent with extended X-ray absorption fine structure spectroscopy and X-ray diffraction data. In conjunction with the QM/MM model of the S1 state, we ...
متن کاملGlutamate-354 of the CP43 polypeptide interacts with the oxygen-evolving Mn4Ca cluster of photosystem II: a preliminary characterization of the Glu354Gln mutant.
In the recent X-ray crystallographic structural models of photosystem II, Glu354 of the CP43 polypeptide is assigned as a ligand of the O2-evolving Mn4Ca cluster. In this communication, a preliminary characterization of the CP43-Glu354Gln mutant of the cyanobacterium Synechocystis sp. PCC 6803 is presented. The steady-state rate of O2 evolution in the mutant cells is only approximately 20% comp...
متن کاملA model for the water-oxidation and recovery systems of the oxygen-evolving complex.
We propose a model for the water-oxidation and recovery systems of the oxygen-evolving complex (OEC) of the photosystem II (PSII) enzyme. The whole system is constructed from two catalytic cycles, conducted as a tandem reaction: (i) a water-oxidation loop uses cerium(IV) ammonium nitrate as an oxidant to activate a dimanganese complex for water-oxidation and thereby liberate a molecule of O2 an...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Biochemistry
دوره 50 29 شماره
صفحات -
تاریخ انتشار 2011