title: The 8.5 A projection map of the light-harvesting complex I from Rhodospirillum rubrum reveals a ring composed of 16 subunits.
abstract: Two-dimensional crystals from light-harvesting complex I (LHC I) of the purple non-sulfur bacterium Rhodospirillum rubrum have been reconstituted from detergent-solubilized protein complexes. Frozen-hydrated samples have been analysed by electron microscopy. The crystals diffract beyond 8 A and a projection map was calculated to 8.5 A. The projection map shows 16 subunits in a 116 A diameter ring with a 68 A hole in the centre. These dimensions are sufficient to incorporate a reaction centre in vivo. Within each subunit, density for the alpha- and the beta-polypeptide chains is clearly resolved, and the density for the bacteriochlorophylls can be assigned. The experimentally determined structure contradicts models of the LHC I presented so far.
authors.affiliation: MRC Laboratory of Molecular Biology, Cambridge, UK.
authors.forename: S
authors.initials: S
authors.lastname: Karrasch
authors.forename: P A
authors.initials: PA
authors.lastname: Bullough
authors.forename: R
authors.initials: R
authors.lastname: Ghosh
mesh_terms: D003461:Crystallography; D005583:Fourier Analysis; D046911:Macromolecular Substances; D008567:Membranes, Artificial; D008854:Microscopy, Electron / Q000379:methods; D010713:Phosphatidylcholines; D045322:Photosynthetic Reaction Center Complex Proteins / Q000648:ultrastructure*; D012246:Rhodospirillum / Q000648:ultrastructure*
chemical_list: D046911:Macromolecular Substances; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D045322:Photosynthetic Reaction Center Complex Proteins; C017251:1,2-oleoylphosphatidylcholine