title: Structure of Light-Harvesting Aggregates in Individual Chlorosomes.
abstract: Among all photosynthetic organisms, green bacteria have evolved one of the most efficient light-harvesting antenna, the chlorosome, that contains hundreds of thousands of bacteriochlorophyll molecules, allowing these bacteria to grow photosynthetically by absorbing only a few photons per bacteriochlorophyll molecule per day. In contrast to other photosynthetic light-harvesting antenna systems, for which a protein scaffold imposes the proper positioning of the chromophores with respect to each other, in chlorosomes, this is accomplished solely by self-assembly. This has aroused enormous interest in the structure-function relations of these assemblies, as they can serve as blueprints for artificial light harvesting systems. In spite of these efforts, conclusive structural information is not available yet, reflecting the sample heterogeneity inherent to the natural system. Here we combine mutagenesis, polarization-resolved single-particle fluorescence-excitation spectroscopy, cryo-electron microscopy, and theoretical modeling to study the chlorosomes of the green sulfur bacterium Chlorobaculum tepidum. We demonstrate that only the combination of these techniques yields unambiguous information on the structure of the bacteriochlorophyll aggregates within the chlorosomes. Moreover, we provide a quantitative estimate of the curvature variation of these aggregates that explains ongoing debates concerning the chlorosome structure.
authors.affiliation: Experimental Physics IV, University of Bayreuth , D-95440 Bayreuth, Germany.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Günther
authors.affiliation: Experimental Physics IV, University of Bayreuth , D-95440 Bayreuth, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Jendrny
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.
authors.forename: Erik A
authors.initials: EA
authors.lastname: Bloemsma
authors.affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Marcus
authors.initials: M
authors.lastname: Tank
authors.affiliation: Groningen Biomolecular Sciences and Biotechnology Institute , Nijenborgh 7, 9747 AG Groningen, The Netherlands.
authors.forename: Gert T
authors.initials: GT
authors.lastname: Oostergetel
authors.affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.|Department of Chemistry and Biochemistry, Montana State University , Bozeman, Montana 59717, United States.
authors.forename: Donald A
authors.initials: DA
authors.lastname: Bryant
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.
authors.forename: Jasper
authors.initials: J
authors.lastname: Knoester
authors.affiliation: Experimental Physics IV, University of Bayreuth , D-95440 Bayreuth, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Köhler
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001429:Bacteriochlorophylls / Q000737:chemistry; D019414:Chlorobi / Q000378:metabolism*; D020285:Cryoelectron Microscopy; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016296:Mutagenesis; D013050:Spectrometry, Fluorescence
chemical_list: D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; D045342:Light-Harvesting Protein Complexes