title: Where water is oxidized to dioxygen: structure of the photosynthetic Mn4Ca cluster.
abstract: The oxidation of water to dioxygen is catalyzed within photosystem II (PSII) by a Mn(4)Ca cluster, the structure of which remains elusive. Polarized extended x-ray absorption fine structure (EXAFS) measurements on PSII single crystals constrain the Mn(4)Ca cluster geometry to a set of three similar high-resolution structures. Combining polarized EXAFS and x-ray diffraction data, the cluster was placed within PSII, taking into account the overall trend of the electron density of the metal site and the putative ligands. The structure of the cluster from the present study is unlike either the 3.0 or 3.5 angstrom-resolution x-ray structures or other previously proposed models.
authors.affiliation: Melvin Calvin Laboratory, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
authors.forename: Junko
authors.initials: J
authors.lastname: Yano
authors.forename: Jan
authors.initials: J
authors.lastname: Kern
authors.forename: Kenneth
authors.initials: K
authors.lastname: Sauer
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Latimer
authors.forename: Yulia
authors.initials: Y
authors.lastname: Pushkar
authors.forename: Jacek
authors.initials: J
authors.lastname: Biesiadka
authors.forename: Bernhard
authors.initials: B
authors.lastname: Loll
authors.forename: Wolfram
authors.initials: W
authors.lastname: Saenger
authors.forename: Johannes
authors.initials: J
authors.lastname: Messinger
authors.forename: Athina
authors.initials: A
authors.lastname: Zouni
authors.forename: Vittal K
authors.initials: VK
authors.lastname: Yachandra
mesh_terms: D001665:Binding Sites; D002118:Calcium / Q000737:chemistry*; D003460:Crystallization; D018360:Crystallography, X-Ray; D000458:Cyanobacteria / Q000737:chemistry* / Q000378:metabolism; D005583:Fourier Analysis; D008024:Ligands; D008345:Manganese / Q000737:chemistry*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism; D013057:Spectrum Analysis; D014867:Water / Q000737:chemistry* / Q000378:metabolism; D014961:X-Ray Diffraction; D014965:X-Rays
chemical_list: D008024:Ligands; D045332:Photosystem II Protein Complex; D014867:Water; D008345:Manganese; D010100:Oxygen; D002118:Calcium