title: Solution structure and excitation energy transfer in phycobiliproteins of Acaryochloris marina investigated by small angle scattering.
abstract: The structure of phycobiliproteins of the cyanobacterium Acaryochloris marina was investigated in buffer solution at physiological temperatures, i.e. under the same conditions applied in spectroscopic experiments, using small angle neutron scattering. The scattering data of intact phycobiliproteins in buffer solution containing phosphate can be well described using a cylindrical shape with a length of about 225Å and a diameter of approximately 100Å. This finding is qualitatively consistent with earlier electron microscopy studies reporting a rod-like shape of the phycobiliproteins with a length of about 250 (M. Chen et al., FEBS Letters 583, 2009, 2535) or 300Å (J. Marquart et al., FEBS Letters 410, 1997, 428). In contrast, phycobiliproteins dissolved in buffer lacking phosphate revealed a splitting of the rods into cylindrical subunits with a height of 28Å only, but also a pronounced sample aggregation. Complementary small angle neutron and X-ray scattering experiments on phycocyanin suggest that the cylindrical subunits may represent either trimeric phycocyanin or trimeric allophycocyanin. Our findings are in agreement with the assumption that a phycobiliprotein rod with a total height of about 225Å can accommodate seven trimeric phycocyanin subunits and one trimeric allophycocyanin subunit, each of which having a height of about 28Å. The structural information obtained by small angle neutron and X-ray scattering can be used to interpret variations in the low-energy region of the 4.5K absorption spectra of phycobiliproteins dissolved in buffer solutions containing and lacking phosphate, respectively.
authors.affiliation: Institute of Physics, University of Tartu, Tartu, Estonia.
authors.forename: M
authors.initials: M
authors.lastname: Golub
authors.affiliation: Laboratoire Léon-Brillouin, CEA-CNRS, Université Paris-Saclay, CEA-Saclay, F-91191 Gif-sur-Yvette, France.
authors.forename: S
authors.initials: S
authors.lastname: Combet
authors.affiliation: Institute for Metalic Biomaterials, Helmholtz Zentrum Geesthacht, 21502 Geesthacht, Germany.
authors.forename: D C F
authors.initials: DCF
authors.lastname: Wieland
authors.affiliation: Joint Institute for Nuclear Research, Dubna, Russia; Moscow Institute of Physics and Technology, Dolgoprudny, Russia; Institute for Safety Problems of Nuclear Power Plants NAS of Ukraine, Kyiv, Ukraine.
authors.forename: D
authors.initials: D
authors.lastname: Soloviov
authors.affiliation: Joint Institute for Nuclear Research, Dubna, Russia; Moscow Institute of Physics and Technology, Dolgoprudny, Russia.
authors.forename: A
authors.initials: A
authors.lastname: Kuklin
authors.affiliation: Department of Chemical Physics and Optics, Charles University, Prague, Ke Karlovu 3, 121 16 Prague, Czech Republic.
authors.forename: H
authors.initials: H
authors.lastname: Lokstein
authors.affiliation: Max-Volmer-Laboratories for Biophysical Chemistry, Technical University Berlin, Germany.
authors.forename: F-J
authors.initials: FJ
authors.lastname: Schmitt
authors.affiliation: Max-Volmer-Laboratories for Biophysical Chemistry, Technical University Berlin, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Olliges
authors.affiliation: Institute of Physics, University of Tartu, Tartu, Estonia.
authors.forename: M
authors.initials: M
authors.lastname: Hecht
authors.affiliation: Max-Volmer-Laboratories for Biophysical Chemistry, Technical University Berlin, Germany.
authors.forename: H-J
authors.initials: HJ
authors.lastname: Eckert
authors.affiliation: Institute of Physics, University of Tartu, Tartu, Estonia. Electronic address: pieper@ut.ee.
authors.forename: J
authors.initials: J
authors.lastname: Pieper
mesh_terms: D000458:Cyanobacteria / Q000737:chemistry*; D004735:Energy Transfer; D033363:Neutron Diffraction; D052979:Phycobiliproteins / Q000737:chemistry; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: D052979:Phycobiliproteins
keywords: Acaryochloris marina; Excitation energy transfer; Phycobiliproteins; Small angle X-ray scattering; Small angle neutron scattering