title: Architecture of the photosynthetic oxygen-evolving center.
abstract: Photosynthesis uses light energy to drive the oxidation of water at an oxygen-evolving catalytic site within photosystem II (PSII). We report the structure of PSII of the cyanobacterium Thermosynechococcus elongatus at 3.5 angstrom resolution. We have assigned most of the amino acid residues of this 650-kilodalton dimeric multisubunit complex and refined the structure to reveal its molecular architecture. Consequently, we are able to describe details of the binding sites for cofactors and propose a structure of the oxygen-evolving center (OEC). The data strongly suggest that the OEC contains a cubane-like Mn3CaO4 cluster linked to a fourth Mn by a mono-micro-oxo bridge. The details of the surrounding coordination sphere of the metal cluster and the implications for a possible oxygen-evolving mechanism are discussed.
authors.affiliation: Department of Biological Sciences, Imperial College London, London, SW7 2AZ, UK.
authors.forename: Kristina N
authors.initials: KN
authors.lastname: Ferreira
authors.forename: Tina M
authors.initials: TM
authors.lastname: Iverson
authors.forename: Karim
authors.initials: K
authors.lastname: Maghlaoui
authors.forename: James
authors.initials: J
authors.lastname: Barber
authors.forename: So
authors.initials: S
authors.lastname: Iwata
mesh_terms: D001665:Binding Sites; D002118:Calcium / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D002338:Carotenoids / Q000737:chemistry / Q000378:metabolism; D002734:Chlorophyll / Q000737:chemistry / Q000378:metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray; D000458:Cyanobacteria / Q000201:enzymology*; D019281:Dimerization; D004579:Electron Transport; D005609:Free Radicals; D006639:Histidine / Q000737:chemistry / Q000378:metabolism; D006860:Hydrogen Bonding; D008024:Ligands; D008345:Manganese / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D008956:Models, Chemical; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D014867:Water / Q000378:metabolism*; D019207:beta Carotene / Q000737:chemistry / Q000378:metabolism
chemical_list: D005609:Free Radicals; D008024:Ligands; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D021122:Protein Subunits; C083100:photosystem II, chlorophyll binding protein, CP-43; C114979:tyrosyl radical YZ; D019207:beta Carotene; D014867:Water; D002734:Chlorophyll; D002338:Carotenoids; D014443:Tyrosine; D008345:Manganese; D006639:Histidine; D010100:Oxygen; D002118:Calcium