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.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Binding Sites
-
Calcium / analysis
-
Calcium / chemistry
-
Calcium / metabolism
-
Carotenoids / chemistry
-
Carotenoids / metabolism
-
Chlorophyll / chemistry
-
Chlorophyll / metabolism
-
Crystallization
-
Crystallography, X-Ray
-
Cyanobacteria / enzymology*
-
Dimerization
-
Electron Transport
-
Free Radicals
-
Histidine / chemistry
-
Histidine / metabolism
-
Hydrogen Bonding
-
Ligands
-
Manganese / analysis
-
Manganese / chemistry
-
Manganese / metabolism
-
Models, Chemical
-
Models, Molecular
-
Oxidation-Reduction
-
Oxygen / metabolism*
-
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
-
Tyrosine / analogs & derivatives*
-
Tyrosine / chemistry
-
Tyrosine / metabolism
-
Water / metabolism*
-
beta Carotene / chemistry
-
beta Carotene / metabolism
Substances
-
Free Radicals
-
Ligands
-
Photosynthetic Reaction Center Complex Proteins
-
Photosystem II Protein Complex
-
Protein Subunits
-
photosystem II, chlorophyll binding protein, CP-43
-
tyrosyl radical YZ
-
beta Carotene
-
Water
-
Chlorophyll
-
Carotenoids
-
Tyrosine
-
Manganese
-
Histidine
-
Oxygen
-
Calcium