QM/MM Models of the O2-Evolving Complex of Photosystem II

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• 作者：Eduardo M. Sproviero ; José ; A. Gascó ; n ; James P. McEvoy ; Gary W. Brudvig ; and Victor S. Batista
• 刊名：Journal of Chemical Theory and Computation
• 出版年：2006
• 出版时间：July 2006
• 年：2006
• 卷：2
• 期：4
• 页码：1119 - 1134
• 全文大小：849K
• 年卷期：v.2,no.4(July 2006)
• ISSN：1549-9626

文摘

This paper introduces structural models of the oxygen-evolving complex of photosystem II (PSII) in the dark-stable S₁ state, as well as in the reduced S₀ and oxidized S₂ states,with complete ligation of the metal-oxo cluster by amino acid residues, water, hydroxide, andchloride. The models are developed according to state-of-the-art quantum mechanics/molecularmechanics (QM/MM) hybrid methods, applied in conjunction with the X-ray crystal structure ofPSII from the cyanobacterium Thermosynechococcus elongatus, recently reported at 3.5 Åresolution. Manganese and calcium ions are ligated consistently with standard coordinationchemistry assumptions, supported by biochemical and spectroscopic data. Furthermore, thecalcium-bound chloride ligand is found to be bound in a position consistent with pulsed electronparamagnetic resonance data obtained from acetate-substituted PSII. The ligation of proteinligands includes monodentate coordination of D1-D342, CP43-E354, and D1-D170 to Mn(1),Mn(3), and Mn(4), respectively; mages/gifchars/eta.gif" BORDER=0 >² coordination of D1-E333 to both Mn(3) and Mn(2); and ligationof D1-E189 and D1-H332 to Mn(2). The resulting QM/MM structural models are consistent withavailable mechanistic data and also are compatible with X-ray diffraction models and extendedX-ray absorption fine structure measurements of PSII. It is, therefore, conjectured that theproposed QM/MM models are particularly relevant to the development and validation of catalyticwater-oxidation intermediates.