Architecture of the Photosynthetic Oxygen-Evolving Center

• Published in: Science (American Association for the Advancement of Science) 2004-03, Vol.303 (5665), p.1831-1838
• Main Authors: Ferreira, Kristina N., Iverson, Tina M., Maghlaoui, Karim, Barber, James, Iwata, So
• Format: Article
• Language: English
• Subjects: Amino acids; Atoms; beta Carotene - chemistry; beta Carotene - metabolism; Binding Sites; Biochemistry; Biological and medical sciences; Calcium - analysis; Calcium - chemistry; Calcium - metabolism; Carotenoids - chemistry; Carotenoids - metabolism; Chemical properties; Chlorophyll - chemistry; Chlorophyll - metabolism; Chlorophylls; Crystalline structure; Crystallization; Crystallography, X-Ray; Cyanobacteria - enzymology; Cyanophyta; Dimerization; Electron transfer; Electron Transport; Electrons; Free Radicals; Fundamental and applied biological sciences. Psychology; Histidine - chemistry; Histidine - metabolism; Hydrogen Bonding; Hydrogen bonds; Ligands; Manganese - analysis; Manganese - chemistry; Manganese - metabolism; Models, Chemical; Models, Molecular; Molecular biophysics; Molecular structure; Molecules; Oxidation; Oxidation-Reduction; Oxygen - metabolism; Oxygen evolving complex; Photosynthesis; Photosynthetic Reaction Center Complex Proteins - chemistry; Photosynthetic Reaction Center Complex Proteins - metabolism; Photosystem II Protein Complex - chemistry; Photosystem II Protein Complex - metabolism; Protein Conformation; Protein Structure, Quaternary; Protein Structure, Secondary; Protein Structure, Tertiary; Protein Subunits - chemistry; Structure in molecular biology; Thermosynechococcus elongatus; Tyrosine - analogs & derivatives; Tyrosine - chemistry; Tyrosine - metabolism; Water; Water - metabolism
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1093087

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$Mn_3CaO_4$cluster linked to a fourth Mn by a$mono-\mu-oxo$bridge. The details of the surrounding coordination sphere of the metal cluster and the implications for a possible oxygen-evolving mechanism are discussed.