title: The architecture of Rhodobacter sphaeroides chromatophores.
abstract: The chromatophores of Rhodobacter (Rb.) sphaeroides represent a minimal bio-energetic system, which efficiently converts light energy into usable chemical energy. Despite extensive studies, several issues pertaining to the morphology and molecular architecture of this elemental energy conversion system remain controversial or unknown. To tackle these issues, we combined electron microscope tomography, immuno-electron microscopy and atomic force microscopy. We found that the intracellular Rb. sphaeroides chromatophores form a continuous reticulum rather than existing as discrete vesicles. We also found that the cytochrome bc1 complex localizes to fragile chromatophore regions, which most likely constitute the tubular structures that interconnect the vesicles in the reticulum. In contrast, the peripheral light-harvesting complex 2 (LH2) is preferentially hexagonally packed within the convex vesicular regions of the membrane network. Based on these observations, we propose that the bc1 complexes are in the inter-vesicular regions and surrounded by reaction center (RC) core complexes, which in turn are bounded by arrays of peripheral antenna complexes. This arrangement affords rapid cycling of electrons between the core and bc1 complexes while maintaining efficient excitation energy transfer from LH2 domains to the RCs.
authors.affiliation: U1006 INSERM, Aix-Marseille Université, Parc Scientifique de Luminy, Marseille F-13009, France. Electronic address: simon.scheuring@inserm.fr.
authors.forename: Simon
authors.initials: S
authors.lastname: Scheuring
authors.affiliation: Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Reinat
authors.initials: R
authors.lastname: Nevo
authors.affiliation: U1006 INSERM, Aix-Marseille Université, Parc Scientifique de Luminy, Marseille F-13009, France.
authors.forename: Lu-Ning
authors.initials: LN
authors.lastname: Liu
authors.affiliation: UMR168 CNRS, Institut Curie, 26 rue d'Ulm, 75005 Paris, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Mangenot
authors.affiliation: Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Dana
authors.initials: D
authors.lastname: Charuvi
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, IBPS, F-75005 Paris, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Boudier
authors.affiliation: LISM CNRS, Aix-Marseille Université, 31 Chemin Joseph Aiguier, 13402 Marseille, France.
authors.forename: Valerie
authors.initials: V
authors.lastname: Prima
authors.affiliation: LISM CNRS, Aix-Marseille Université, 31 Chemin Joseph Aiguier, 13402 Marseille, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Hubert
authors.affiliation: LISM CNRS, Aix-Marseille Université, 31 Chemin Joseph Aiguier, 13402 Marseille, France.
authors.forename: James N
authors.initials: JN
authors.lastname: Sturgis
authors.affiliation: Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Ziv
authors.initials: Z
authors.lastname: Reich
mesh_terms: D002856:Chromatophores / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure*; D003593:Cytoplasm / Q000378:metabolism; D004735:Energy Transfer / Q000235:genetics*; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry / Q000648:ultrastructure; D018625:Microscopy, Atomic Force; D010788:Photosynthesis; D012242:Rhodobacter sphaeroides / Q000254:growth & development / Q000378:metabolism*
chemical_list: D045342:Light-Harvesting Protein Complexes
keywords: Atomic force microscopy; Electron tomography; Light-harvesting complex; Membrane structure; Reaction center