title: Architecture of the native photosynthetic apparatus of Phaeospirillum molischianum.
abstract: The ubiquity and importance of photosynthetic organisms in nature has made the molecular mechanisms of photosynthesis a widely studied subject at both structural and functional levels. A current challenge is to understand the supramolecular assembly of the proteins involved in photosynthesis in native membranes. We have used atomic force microscopy to study the architecture of the photosynthetic apparatus and analyze the structure of single molecules in chromatophores of Phaeospirillum molischianum. Core complexes are formed by the reaction center enclosed by an elliptical light harvesting complex 1. LH2 are octameric rings, assembled either with cores or in hexagonally packed LH2 antenna domains. The symmetry mismatch caused by octameric LH2 packing in a hexagonal lattice, that could be avoided in a square lattice, suggests lipophobic effects rather than specific inter-molecular interactions drive protein organization. The core and LH2 complexes are organized to form a supramolecular assembly reminiscent to that found in Rhodospirillum photometricum, and very different from that observed in Rhodobacter sphaeroides, Rb. blasticus, and Blastochloris viridis.
authors.affiliation: Institut Curie, UMR-CNRS 168, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05, France.
authors.forename: Rui Pedro
authors.initials: RP
authors.lastname: Gonçalves
authors.forename: Alain
authors.initials: A
authors.lastname: Bernadac
authors.forename: James N
authors.initials: JN
authors.lastname: Sturgis
authors.forename: Simon
authors.initials: S
authors.lastname: Scheuring
mesh_terms: D020130:Bacterial Chromatophores / Q000737:chemistry / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000737:chemistry / Q000648:ultrastructure; D002458:Cell Fractionation; D002499:Centrifugation, Density Gradient; D004735:Energy Transfer; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry / Q000648:ultrastructure; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D009097:Multienzyme Complexes / Q000737:chemistry / Q000648:ultrastructure; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000648:ultrastructure*; D012246:Rhodospirillum / Q000737:chemistry / Q000201:enzymology*; D013053:Spectrophotometry
chemical_list: C081521:B800-850 light-harvesting complex, bacteria; D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D009097:Multienzyme Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; C094744:light-harvesting complex 1, Rhodospirillum