title: The purple Trp288Ala mutant of Synechocystis OCP persistently quenches phycobilisome fluorescence and tightly interacts with FRP.
abstract: In Cyanobacteria, the Orange Carotenoid Protein (OCP) and Fluorescence Recovery Protein (FRP) are central to the photoprotective mechanism consisting in regulated quenching of phycobilisome (PBs) fluorescence. Due to a transient and flexible nature of the light-activated red quenching form, OCPR, which is obtained from the stable dark-adapted orange form, OCPO, by photoconversion, the detailed mechanism of photoprotection remains unclear. Here we demonstrate that our recently described W288A mutant of the Synechocystis OCP (hereinafter called OCPW288A) is a fully functional analogue of the OCPRform which is capable of constitutive PBs fluorescence quenching in vitro with no need of photoactivation. This PBs quenching effect is abolished in the presence of FRP, which interacts with OCPW288Awith micromolar affinity and an apparent stoichiometry of 1:1, unexpectedly, implying dissociation of the FRP dimers. This establishes OCPW288Aas a robust model system providing novel insights into the interplay between OCP and FRP to regulate photoprotection in cyanobacteria.
authors.affiliation: A.N. Bach Institute of Biochemistry, Federal Research Center "Fundamentals of Biotechnology" of the Russian Academy of Sciences, 119071 Moscow, Russia. Electronic address: nikolai.sluchanko@mail.ru.
authors.forename: Nikolai N
authors.initials: NN
authors.lastname: Sluchanko
authors.affiliation: Department of Biophysics, Faculty of Biology, M.V. Lomonosov Moscow State University, 119992, 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, 119992 Moscow, Russia.
authors.forename: Evgeny A
authors.initials: EA
authors.lastname: Shirshin
authors.affiliation: Department of Biophysics, Faculty of Biology, M.V. Lomonosov Moscow State University, 119992, Moscow, Russia.
authors.forename: Georgy V
authors.initials: GV
authors.lastname: Tsoraev
authors.affiliation: Technical University of Berlin, Institute of Chemistry PC 14, Straße des 17. Juni 135, D-10623 Berlin, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Friedrich
authors.affiliation: Department of Biophysics, Faculty of Biology, M.V. Lomonosov Moscow State University, 119992, Moscow, Russia.
authors.forename: Eugene G
authors.initials: EG
authors.lastname: Maksimov
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D002338:Carotenoids / Q000378:metabolism; D005453:Fluorescence; D008027:Light; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D045524:Phycobilisomes / Q000378:metabolism*; D055503:Protein Multimerization / Q000502:physiology; D046939:Synechocystis / Q000235:genetics* / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D045524:Phycobilisomes; C109473:orange carotenoid protein, Synechocystis; D002338:Carotenoids
keywords: Echinenone; Orange carotenoid protein; Protein-protein interaction; Size-exclusion chromatography; Synechocystis sp. PCC 6803