title: In situ high-resolution structure of the baseplate antenna complex in Chlorobaculum tepidum.
abstract: Photosynthetic antenna systems enable organisms harvesting light and transfer the energy to the photosynthetic reaction centre, where the conversion to chemical energy takes place. One of the most complex antenna systems, the chlorosome, found in the photosynthetic green sulfur bacterium Chlorobaculum (Cba.) tepidum contains a baseplate, which is a scaffolding super-structure, formed by the protein CsmA and bacteriochlorophyll a. Here we present the first high-resolution structure of the CsmA baseplate using intact fully functional, light-harvesting organelles from Cba. tepidum, following a hybrid approach combining five complementary methods: solid-state NMR spectroscopy, cryo-electron microscopy, isotropic and anisotropic circular dichroism and linear dichroism. The structure calculation was facilitated through development of new software, GASyCS for efficient geometry optimization of highly symmetric oligomeric structures. We show that the baseplate is composed of rods of repeated dimers of the strongly amphipathic CsmA with pigments sandwiched within the dimer at the hydrophobic side of the helix.
authors.affiliation: Center for Insoluble Protein Structures (inSPIN), Aarhus C DK-8000, Denmark.|Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, Aarhus C DK-8000, Denmark.|Department of Chemistry, Aarhus C DK-8000, Denmark.
authors.forename: Jakob Toudahl
authors.initials: JT
authors.lastname: Nielsen
authors.affiliation: Center for Insoluble Protein Structures (inSPIN), Aarhus C DK-8000, Denmark.|Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, Aarhus C DK-8000, Denmark.|Department of Chemistry, Aarhus C DK-8000, Denmark.
authors.forename: Natalia V
authors.initials: NV
authors.lastname: Kulminskaya
authors.affiliation: Center for Insoluble Protein Structures (inSPIN), Aarhus C DK-8000, Denmark.|Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, Aarhus C DK-8000, Denmark.|Department of Chemistry, Aarhus C DK-8000, Denmark.
authors.forename: Morten
authors.initials: M
authors.lastname: Bjerring
authors.affiliation: Institute of Physics, University of Tartu, W. Ostwaldi Street 1, Tartu 50411, Estonia.
authors.forename: Juha M
authors.initials: JM
authors.lastname: Linnanto
authors.affiliation: Institute of Physics, University of Tartu, W. Ostwaldi Street 1, Tartu 50411, Estonia.
authors.forename: Margus
authors.initials: M
authors.lastname: Rätsep
authors.affiliation: Center for Insoluble Protein Structures (inSPIN), Aarhus C DK-8000, Denmark.|Novo Nordisk a/s, Novo Nordisk Park, Måløv 2760, Denmark.
authors.forename: Marie Østergaard
authors.initials: MØ
authors.lastname: Pedersen
authors.affiliation: Hungarian Academy of Sciences, Biological Research Centre, Temesvári krt. 62, Szeged 6726, Hungary.
authors.forename: Petar H
authors.initials: PH
authors.lastname: Lambrev
authors.affiliation: Hungarian Academy of Sciences, Biological Research Centre, Temesvári krt. 62, Szeged 6726, Hungary.
authors.forename: Márta
authors.initials: M
authors.lastname: Dorogi
authors.affiliation: Hungarian Academy of Sciences, Biological Research Centre, Temesvári krt. 62, Szeged 6726, Hungary.
authors.forename: Győző
authors.initials: G
authors.lastname: Garab
authors.affiliation: Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, Aarhus C DK-8000, Denmark.
authors.forename: Karen
authors.initials: K
authors.lastname: Thomsen
authors.affiliation: Karolinska Institutet, Department of Biosciences and Medical Nutrition, Hälsovägen 7, Huddinge 141 83, Sweden.
authors.forename: Caroline
authors.initials: C
authors.lastname: Jegerschöld
authors.affiliation: Section for Marine Biology, Department of Biology, University of Copenhagen, Strandpromenaden 5, Helsingør DK-3000, Denmark.
authors.forename: Niels-Ulrik
authors.initials: NU
authors.lastname: Frigaard
authors.affiliation: Karolinska Institutet, Department of Biosciences and Medical Nutrition, Hälsovägen 7, Huddinge 141 83, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Lindahl
authors.affiliation: Center for Insoluble Protein Structures (inSPIN), Aarhus C DK-8000, Denmark.|Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, Aarhus C DK-8000, Denmark.|Department of Chemistry, Aarhus C DK-8000, Denmark.
authors.forename: Niels Chr
authors.initials: NC
authors.lastname: Nielsen
mesh_terms: D016880:Anisotropy; D019414:Chlorobi / Q000378:metabolism / Q000648:ultrastructure*; D002942:Circular Dichroism; D020285:Cryoelectron Microscopy; D021621:Imaging, Three-Dimensional; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry / Q000648:ultrastructure*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015388:Organelles / Q000378:metabolism / Q000648:ultrastructure; D015203:Reproducibility of Results
chemical_list: D045342:Light-Harvesting Protein Complexes