title: Structural changes of the oxygen-evolving complex in photosystem II during the catalytic cycle.
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.
authors.affiliation: Institut für Chemie/Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universität Berlin, D-10623 Berlin, Germany.
authors.forename: Carina
authors.initials: C
authors.lastname: Glöckner
authors.forename: Jan
authors.initials: J
authors.lastname: Kern
authors.forename: Matthias
authors.initials: M
authors.lastname: Broser
authors.forename: Athina
authors.initials: A
authors.lastname: Zouni
authors.forename: Vittal
authors.initials: V
authors.lastname: Yachandra
authors.forename: Junko
authors.initials: J
authors.lastname: Yano
mesh_terms: D002384:Catalysis; D010100:Oxygen / Q000737:chemistry*; D045332:Photosystem II Protein Complex / Q000737:chemistry*
chemical_list: D045332:Photosystem II Protein Complex; D010100:Oxygen
keywords: Dioxygen; Manganese; Metalloenzymes; Photosynthesis; Photosystem II; Water Oxidation; X-ray Absorption Spectroscopy; X-ray Photoreduction