Structural Changes of the Oxygen-evolving Complex in Photosystem II during the Catalytic Cycle |
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Authors: | Carina Gl?ckner Jan Kern Matthias Broser Athina Zouni Vittal Yachandra Junko Yano |
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Institution: | From the ‡Institut für Chemie/Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universität Berlin, D-10623 Berlin, Germany and ;the §Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 |
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Abstract: | The oxygen-evolving complex (OEC) in the membrane-bound protein complex photosystem II (PSII) catalyzes the water oxidation reaction that takes place in oxygenic photosynthetic organisms. We investigated the structural changes of the Mn4CaO5 cluster in the OEC during the S state transitions using x-ray absorption spectroscopy (XAS). Overall structural changes of the Mn4CaO5 cluster, based on the manganese ligand and Mn-Mn distances obtained from this study, were incorporated into the geometry of the Mn4CaO5 cluster in the OEC obtained from a polarized XAS model and the 1.9-Å high resolution crystal structure. Additionally, we compared the S1 state XAS of the dimeric and monomeric form of PSII from Thermosynechococcus elongatus and spinach PSII. Although the basic structures of the OEC are the same for T. elongatus PSII and spinach PSII, minor electronic structural differences that affect the manganese K-edge XAS between T. elongatus PSII and spinach PSII are found and may originate from differences in the second sphere ligand atom geometry. |
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Keywords: | Manganese Metalloenzymes Photosynthesis Photosystem II X-ray Absorption Spectroscopy Dioxygen Water Oxidation X-ray Photoreduction |
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