title: Electronic structure of S(2) state of the oxygen-evolving complex of photosystem II studied by PELDOR.
abstract: Photosynthetic water splitting is catalyzed by a Mn(4)CaO(5) cluster in photosystem II, whose structure was recently determined at a resolution of 1.9Å [Umena, Y. et al. 2011, Nature, 473:55-60]. To determine the electronic structure of the Mn(4)CaO(5) cluster, pulsed electron-electron double resonance (PELDOR) measurements were performed for the tyrosine residue Y(D)() and S(2) state signals with non-oriented and oriented photosystem II (PS II) samples. Based on these measurements, the spin density distributions were calculated by comparing with the experimental results. The best fitting parameters were obtained with a model in which Mn1 has a large positive projection, Mn3 has a small positive projection, and Mn2 and Mn4 have negative projections (the numbering of Mni (i=1-4) is based on the crystal structure at a 1.9Å resolution), which yielded spin projections of 1.97, -1.20, 1.19 and -0.96 for Mn1-4 ions. The results show that the Mn1 ion, which is coordinated by H332, D342 and E189, has a valence of Mn(III) in the S(2) state. The sign of the exchange interactions J(13) is positive, and the other signs are negative.
authors: Graduate school of Science, Nagoya University, Chikusa, Nagoya, Japan.
authors: Mizue
authors: M
authors: Asada
authors: Hiroki
authors: H
authors: Nagashima
authors: Faisal Hammad Mekky
authors: FH
authors: Koua
authors: Jian-Ren
authors: JR
authors: Shen
authors: Asako
authors: A
authors: Kawamori
authors: Hiroyuki
authors: H
authors: Mino
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D010100:Oxygen / Q000737:chemistry*; D045332:Photosystem II Protein Complex / Q000737:chemistry*
chemical_list: D045332:Photosystem II Protein Complex; D010100:Oxygen