title: Structure of the LH1-RC complex from Thermochromatium tepidum at 3.0 Å.
abstract: The light-harvesting core antenna (LH1) and the reaction centre (RC) of purple photosynthetic bacteria form a supramolecular complex (LH1-RC) to use sunlight energy in a highly efficient manner. Here we report the first near-atomic structure, to our knowledge, of a LH1-RC complex, namely that of a Ca(2+)-bound complex from Thermochromatium tepidum, which reveals detailed information on the arrangement and interactions of the protein subunits and the cofactors. The RC is surrounded by 16 heterodimers of the LH1 αβ-subunit that form a completely closed structure. The Ca(2+) ions are located at the periplasmic side of LH1. Thirty-two bacteriochlorophyll and 16 spirilloxanthin molecules in the LH1 ring form an elliptical assembly. The geometries of the pigment assembly involved in the absorption characteristics of the bacteriochlorophyll in LH1 and excitation energy transfer among the pigments are reported. In addition, possible ubiquinone channels in the closed LH1 complex are proposed based on the atomic structure.
authors.affiliation: 1] Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan [2].
authors.forename: Satomi
authors.initials: S
authors.lastname: Niwa
authors.affiliation: 1] Faculty of Science, Ibaraki University, Mito, Ibaraki 310-8512, Japan [2].
authors.forename: Long-Jiang
authors.initials: LJ
authors.lastname: Yu
authors.affiliation: 1] Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan [2].
authors.forename: Kazuki
authors.initials: K
authors.lastname: Takeda
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Hirano
authors.affiliation: Faculty of Science, Ibaraki University, Mito, Ibaraki 310-8512, Japan.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Kawakami
authors.affiliation: Faculty of Science, Ibaraki University, Mito, Ibaraki 310-8512, Japan.
authors.forename: Zheng-Yu
authors.initials: ZY
authors.lastname: Wang-Otomo
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Kunio
authors.initials: K
authors.lastname: Miki
mesh_terms: D001429:Bacteriochlorophylls / Q000737:chemistry / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002841:Chromatiaceae / Q000737:chemistry*; D003067:Coenzymes / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D014451:Ubiquinone / Q000378:metabolism; D024341:Xanthophylls / Q000737:chemistry / Q000378:metabolism
chemical_list: D001429:Bacteriochlorophylls; D003067:Coenzymes; D045342:Light-Harvesting Protein Complexes; D021122:Protein Subunits; D024341:Xanthophylls; D014451:Ubiquinone; C055255:spirilloxanthin; D002118:Calcium