Protective dissipation of excess absorbed energy by photosynthetic apparatus of cyanobacteria: role of antenna terminal emitters |
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Authors: | Navassard V Karapetyan |
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Institution: | (1) A.N. Bakh Institute of Biochemistry, Russian Academy of Sciences, Leninsky pr. 33, Moscow, 119071, Russia |
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Abstract: | Two mechanisms of photoprotective dissipation of the excessively absorbed energy by photosynthetic apparatus of cyanobacteria
are described that divert energy from reaction centers. Energy dissipation, monitored as nonphotochemical fluorescence quenching,
occurs at different steps of energy transfer within the phycobilisomes or core antenna of photosystem I. Although these mechanisms
differ significantly, in both cases, energy dissipates mainly from terminal emitters: allophycocyanin B or core membrane linker
protein (LCM) in phycobilisomes, or the longest-wavelength chlorophylls in photosystem I antenna. It is supposed that carotenoid-induced
energy dissipation in phycobilisomes is triggered by light-induced transformation of the nonquenched state of antenna into
quenched state due to conformation changes caused by orange carotinoid-binding protein (OCP)–phycobilisome interaction. Fluorescence
of the longest-wavelength chlorophylls of photosystem I antenna is strongly quenched by P700 cation radical or by P700 triplet
state, dependent on redox state of the acceptor side cofactors of photosystem I. |
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Keywords: | Energy dissipation Fluorescence quenching Long-wavelength chlorophyll Phycobilisomes Photosystem I Terminal emitter |
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