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Magdaong NCM, Blankenship RE. Photoprotective, excited-state quenching mechanisms in diverse photosynthetic organisms. J Biol Chem 2018; 293:5018-5025. [PMID: 29298897 DOI: 10.1074/jbc.tm117.000233] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Light-harvesting complexes (LHCs) serve a dual role in photosynthesis, depending on the prevailing light conditions. In low light, they ensure photosynthetic efficiency by maximizing the light absorption cross-section and subsequent energy storage. Under excess light conditions, LHCs perform photoprotective quenching functions to prevent harmful chemical species such as triplet chlorophyll and singlet oxygen from forming and damaging the photosynthetic apparatus. In this Minireview, various photoprotective quenching mechanisms that have been identified in different photosynthetic organisms are surveyed and summarized, and implications for improving photosynthetic productivity are briefly discussed.
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Affiliation(s)
- Nikki Cecil M Magdaong
- From the Departments of Biology and Chemistry and.,the Photosynthetic Antenna Research Center, Washington University in Saint Louis, St. Louis, Missouri 63130
| | - Robert E Blankenship
- From the Departments of Biology and Chemistry and .,the Photosynthetic Antenna Research Center, Washington University in Saint Louis, St. Louis, Missouri 63130
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The photocycle of orange carotenoid protein conceals distinct intermediates and asynchronous changes in the carotenoid and protein components. Sci Rep 2017; 7:15548. [PMID: 29138423 PMCID: PMC5686206 DOI: 10.1038/s41598-017-15520-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Accepted: 10/27/2017] [Indexed: 11/30/2022] Open
Abstract
The 35-kDa Orange Carotenoid Protein (OCP) is responsible for photoprotection in cyanobacteria. It acts as a light intensity sensor and efficient quencher of phycobilisome excitation. Photoactivation triggers large-scale conformational rearrangements to convert OCP from the orange OCPO state to the red active signaling state, OCPR, as demonstrated by various structural methods. Such rearrangements imply a complete, yet reversible separation of structural domains and translocation of the carotenoid. Recently, dynamic crystallography of OCPO suggested the existence of photocycle intermediates with small-scale rearrangements that may trigger further transitions. In this study, we took advantage of single 7 ns laser pulses to study carotenoid absorption transients in OCP on the time-scale from 100 ns to 10 s, which allowed us to detect a red intermediate state preceding the red signaling state, OCPR. In addition, time-resolved fluorescence spectroscopy and the assignment of carotenoid-induced quenching of different tryptophan residues derived thereof revealed a novel orange intermediate state, which appears during the relaxation of photoactivated OCPR to OCPO. Our results show asynchronous changes between the carotenoid- and protein-associated kinetic components in a refined mechanistic model of the OCP photocycle, but also introduce new kinetic signatures for future studies of OCP photoactivity and photoprotection.
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Maksimov EG, Sluchanko NN, Slonimskiy YB, Mironov KS, Klementiev KE, Moldenhauer M, Friedrich T, Los DA, Paschenko VZ, Rubin AB. The Unique Protein-to-Protein Carotenoid Transfer Mechanism. Biophys J 2017; 113:402-414. [PMID: 28746851 DOI: 10.1016/j.bpj.2017.06.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Revised: 05/23/2017] [Accepted: 06/02/2017] [Indexed: 11/26/2022] Open
Abstract
Orange Carotenoid Protein (OCP) is known as an effector and regulator of cyanobacterial photoprotection. This 35 kDa water-soluble protein provides specific environment for blue-green light absorbing keto-carotenoids, which excitation causes dramatic but fully reversible rearrangements of the OCP structure, including carotenoid translocation and separation of C- and N-terminal domains upon transition from the basic orange to photoactivated red OCP form. Although recent studies greatly improved our understanding of the OCP photocycle and interaction with phycobilisomes and the fluorescence recovery protein, the mechanism of OCP assembly remains unclear. Apparently, this process requires targeted delivery and incorporation of a highly hydrophobic carotenoid molecule into the water-soluble apoprotein of OCP. Recently, we introduced, to our knowledge, a novel carotenoid carrier protein, COCP, which consists of dimerized C-domain(s) of OCP and can combine with the isolated N-domain to form transient OCP-like species. Here, we demonstrate that in vitro COCP efficiently transfers otherwise tightly bound carotenoid to the full-length OCP apoprotein, resulting in formation of photoactive OCP from completely photoinactive species. We accurately analyze the peculiarities of this process that, to the best of our knowledge, appears unique, a previously uncharacterized protein-to-protein carotenoid transfer mechanism. We hypothesize that a similar OCP assembly can occur in vivo, substantiating specific roles of the COCP carotenoid carrier in cyanobacterial photoprotection.
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Affiliation(s)
- Eugene G Maksimov
- Department of Biophysics, M.V. Lomonosov Moscow State University, Moscow, Russia.
| | - Nikolai N Sluchanko
- Department of Biophysics, M.V. Lomonosov Moscow State University, Moscow, Russia; A.N. Bach Institute of Biochemistry, Federal Research Center of Biotechnology of the Russian Academy of Sciences, Moscow, Russia
| | - Yury B Slonimskiy
- A.N. Bach Institute of Biochemistry, Federal Research Center of Biotechnology of the Russian Academy of Sciences, Moscow, Russia; Department of Biochemistry, M.V. Lomonosov Moscow State University, Moscow, Russia
| | - Kirill S Mironov
- Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Moscow, Russia
| | | | | | - Thomas Friedrich
- Technical University of Berlin, Institute of Chemistry, Berlin, Germany
| | - Dmitry A Los
- Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Moscow, Russia
| | - Vladimir Z Paschenko
- Department of Biophysics, M.V. Lomonosov Moscow State University, Moscow, Russia
| | - Andrew B Rubin
- Department of Biophysics, M.V. Lomonosov Moscow State University, Moscow, Russia
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