title: The Signaling State of Orange Carotenoid Protein.
abstract: Orange carotenoid protein (OCP) is the photoactive protein that is responsible for high light tolerance in cyanobacteria. We studied the kinetics of the OCP photocycle by monitoring changes in its absorption spectrum, intrinsic fluorescence, and fluorescence of the Nile red dye bound to OCP. It was demonstrated that all of these three methods provide the same kinetic parameters of the photocycle, namely, the kinetics of OCP relaxation in darkness was biexponential with a ratio of two components equal to 2:1 independently of temperature. Whereas the changes of the absorption spectrum of OCP characterize the geometry and environment of its chromophore, the intrinsic fluorescence of OCP reveals changes in its tertiary structure, and the fluorescence properties of Nile red indicate the exposure of hydrophobic surface areas of OCP to the solvent following the photocycle. The results of molecular-dynamics studies indicated the presence of two metastable conformations of 3'-hydroxyechinenone, which is consistent with characteristic changes in the Raman spectra. We conclude that rotation of the β-ionylidene ring in the C-terminal domain of OCP could be one of the first conformational rearrangements that occur during photoactivation. The obtained results suggest that the photoactivated form of OCP represents a molten globule-like state that is characterized by increased mobility of tertiary structure elements and solvent accessibility.
authors.affiliation: Department of Biophysics, Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia. Electronic address: emaksimoff@yandex.ru.
authors.forename: Eugene G
authors.initials: EG
authors.lastname: Maksimov
authors.affiliation: Department of Quantum Electronics, Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow, Russia.
authors.forename: Evgeny A
authors.initials: EA
authors.lastname: Shirshin
authors.affiliation: A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow, Russia.
authors.forename: Nikolai N
authors.initials: NN
authors.lastname: Sluchanko
authors.affiliation: Department of Biophysics, Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia.
authors.forename: Dmitry V
authors.initials: DV
authors.lastname: Zlenko
authors.affiliation: Department of Biophysics, Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia.
authors.forename: Evgenia Y
authors.initials: EY
authors.lastname: Parshina
authors.affiliation: Department of Biophysics, Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia.
authors.forename: Georgy V
authors.initials: GV
authors.lastname: Tsoraev
authors.affiliation: Department of Biophysics, Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia.
authors.forename: Konstantin E
authors.initials: KE
authors.lastname: Klementiev
authors.affiliation: Department of Quantum Electronics, Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow, Russia.
authors.forename: Gleb S
authors.initials: GS
authors.lastname: Budylin
authors.affiliation: Institute of Chemistry, Max-Volmer Laboratory of Biophysical Chemistry, Technical University Berlin, Berlin, Germany.
authors.forename: Franz-Josef
authors.initials: FJ
authors.lastname: Schmitt
authors.affiliation: Institute of Chemistry, Max-Volmer Laboratory of Biophysical Chemistry, Technical University Berlin, Berlin, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Friedrich
authors.affiliation: Department of Quantum Electronics, Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow, Russia.
authors.forename: Victor V
authors.initials: VV
authors.lastname: Fadeev
authors.affiliation: Department of Biophysics, Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia.
authors.forename: Vladimir Z
authors.initials: VZ
authors.lastname: Paschenko
authors.affiliation: Department of Biophysics, Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia.
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Rubin
mesh_terms: D065638:Absorption, Radiation; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D000458:Cyanobacteria / Q000737:chemistry; D005456:Fluorescent Dyes / Q000494:pharmacology; D008164:Luminescent Proteins / Q000737:chemistry* / Q000378:metabolism; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D015398:Signal Transduction
chemical_list: D001426:Bacterial Proteins; D005456:Fluorescent Dyes; D008164:Luminescent Proteins