title: Revealing the structure of the oxygen-evolving core dimer of photosystem II by cryoelectron crystallography.
abstract: Here we present cryoelectron crystallographic analysis of an isolated dimeric oxygen-evolving complex of photosystem II (at a resolution of approximately 0.9 nm), revealing that the D1-D2 reaction center (RC) proteins are centrally located between the chlorophyll-binding proteins, CP43 and CP47. This conclusion supports the hypothesis that photosystems I and II have similar structural features and share a common evolutionary origin. Additional density connecting the two halves of the dimer, which was not observed in a recently described CP47-RC complex that did not include CP43, may be attributed to the small subunits that are involved in regulating secondary electron transfer, such as PsbH. These subunits are possibly also required for stabilization of the dimeric photosystem II complex. This complex, containing at least 29 transmembrane helices in its asymmetric unit, represents one of the largest membrane protein complexes studied at this resolution.
authors.affiliation: Biochemistry Department, Imperial College of Science, Technology & Medicine, London, UK.
authors.forename: B
authors.initials: B
authors.lastname: Hankamer
authors.forename: E P
authors.initials: EP
authors.lastname: Morris
authors.forename: J
authors.initials: J
authors.lastname: Barber
mesh_terms: D020285:Cryoelectron Microscopy; D003460:Crystallization; D003461:Crystallography; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D007091:Image Processing, Computer-Assisted; D045342:Light-Harvesting Protein Complexes; D008970:Molecular Weight; D009097:Multienzyme Complexes / Q000737:chemistry / Q000648:ultrastructure; D010100:Oxygen / Q000378:metabolism*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000032:analysis / Q000737:chemistry* / Q000648:ultrastructure; D045332:Photosystem II Protein Complex; D017433:Protein Structure, Secondary
chemical_list: D045342:Light-Harvesting Protein Complexes; D009097:Multienzyme Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; C083100:photosystem II, chlorophyll binding protein, CP-43; C070970:photosystem II, chlorophyll-binding protein, CP-47; D010100:Oxygen