Minireview Photoinhibition – a historical perspective ∗
نویسندگان
چکیده
Photoinhibition is a state of physiological stress that occurs in all oxygen evolving photosynthetic organisms exposed to light. The primary damage occurs within the reaction center of Photosystem II (PS II). While irreversible photoinduced damage to PS II occurs at all light intensities, the efficiency of photosynthetic electron transfer decreases markedly only when the rate of damage exceeds the rate of its repair, which requires de novo PS II protein synthesis. Photoinhibition has been studied for over a century using a large variety of biochemical, biophysical and genetic methodologies. The discovery of the light induced turnover of a protein, encoded by the plastid psbA gene (the D1 protein), later identified as one of the photochemical reaction center II proteins, has led to the elucidation of the underlying mechanism of photoinhibition and to a deeper understanding of the PS II ‘life cycle.’ Abbreviations: bRC – bacterial reaction center; Chl – chlorophyll; DCIP – dichlorophenol-indophenol; DCMU – 3-(3,4, dichlorophenyl) 1,1dimethylurea; EMBO – European Molecular Biology Organization; kDa – kilo Dalton, apparent; LMW – low molecular weight proteins of PS II; NASA – National Aeronautics Space Agency; pD1 precursor – carboxy-terminal unprocessed D1 protein; Pheo – the primary PS II electron acceptor; Pheo.−. – pheophytin anion radical; PI – photoinhibition; PS I, PS II – photosystem I and II respectively; QA – QB – QA.− – QB.− – the primary and secondary electron acceptors quinones of PS II in the oxidized and semiquinone radical form, respectively; RCII – photosystem II reaction center; S2 – S3 – the oxidation states of the manganese cluster of PS II donor side that has lost one or two electrons, respectively; YZ, YZ.− – the tyrosine 161 of the D1 protein in the neutral and anion radical form, respectively
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