title: Structure of the dimeric RC-LH1-PufX complex from Rhodobaca bogoriensis investigated by electron microscopy.
abstract: Electron microscopy and single-particle averaging were performed on isolated reaction centre (RC)-antenna complexes (RC-LH1-PufX complexes) of Rhodobaca bogoriensis strain LBB1, with the aim of establishing the LH1 antenna conformation, and, in particular, the structural role of the PufX protein. Projection maps of dimeric complexes were obtained at 13 Å resolution and show the positions of the 2 × 14 LH1 α- and β-subunits. This new dimeric complex displays two open, C-shaped LH1 aggregates of 13 αβ polypeptides partially surrounding the RCs plus two LH1 units forming the dimer interface in the centre. Between the interface and the two half rings are two openings on each side. Next to the openings, there are four additional densities present per dimer, considered to be occupied by four copies of PufX. The position of the RC in our model was verified by comparison with RC-LH1-PufX complexes in membranes. Our model differs from previously proposed configurations for Rhodobacter species in which the LH1 ribbon is continuous in the shape of an S, and the stoichiometry is of one PufX per RC.
authors.affiliation: Electron Microscopy Group, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, Groningen, The Netherlands.
authors.forename: Dmitry A
authors.initials: DA
authors.lastname: Semchonok
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Chauvin
authors.forename: Raoul N
authors.initials: RN
authors.lastname: Frese
authors.forename: Colette
authors.initials: C
authors.lastname: Jungas
authors.forename: Egbert J
authors.initials: EJ
authors.lastname: Boekema
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000648:ultrastructure; D002462:Cell Membrane / Q000737:chemistry; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000648:ultrastructure*; D008565:Membrane Proteins / Q000737:chemistry / Q000648:ultrastructure; D008854:Microscopy, Electron; D008958:Models, Molecular; D010788:Photosynthesis; D011487:Protein Conformation; D055503:Protein Multimerization; D020560:Proteobacteria / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods
chemical_list: D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins