Reorganization of Substrate Waters between the Closed and Open Cubane Conformers during the S2 to S3 Transition in the Oxygen Evolving Complex

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• 作者：Matteo Capone ; Daniele Bovi ; Daniele Narzi ; Leonardo Guidoni
• 刊名：Biochemistry
• 出版年：2015
• 出版时间：October 27, 2015
• 年：2015
• 卷：54
• 期：42
• 页码：6439-6442
• 全文大小：291K
• ISSN：1520-4995

文摘

A crucial step in the mechanism for oxygen evolution in the Photosystem II complex resides in the transition from the S₂ state to the S₃ state of Kok鈥揓oliot鈥檚 cycle, in which an additional water molecule binds to the cluster. On the basis of computational chemistry calculations on Photosystem II models, we propose a reorganization mechanism involving a hydroxyl (W2) and a 渭₂-oxo bridge (O5) that is able to link the closed cubane S₂^B intermediate conformer to the S₃ open cubane structure. This mechanism can reconcile the apparent conflict between recently reported water exchange and electron paramagnetic resonance experiments, and theoretical studies.