Identification of the electron donor to flavodiiron proteins in Synechocystis sp. PCC 6803 by in vivo spectroscopy - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Biochimica biophysica acta (BBA) - Bioenergetics Année : 2020

Identification of the electron donor to flavodiiron proteins in Synechocystis sp. PCC 6803 by in vivo spectroscopy

Résumé

Flavodiiron proteins (FDPs) of photosynthetic organisms play a photoprotective role by reducing oxygen to water and thus avoiding the accumulation of excess electrons on the photosystem I (PSI) acceptor side under stress conditions. In Synechocystis sp. PCC 6803 grown under high CO 2 , both FDPs Flv1 and Flv3 are indispensable for oxygen reduction. We performed a detailed in vivo kinetic study of wild-type (WT) and flv1/3 strains of Synechocystis using light-induced NADPH fluorescence and near-infrared absorption of ironsulfur clusters from ferredoxin and the PSI acceptors (F A F B), collectively named FeS. These measurements were performed under conditions where the Calvin-Benson cycle is inactive or poorly activated. Under such conditions, the NADPH decay following a short illumination decays in parallel in both strains and exhibits a time lag which is correlated to the presence of reduced FeS. On the contrary, reduced FeS decays much faster in WT than in flv1/3 (13 vs 2 s-1). These data unambiguously show that reduced ferredoxin, or possibly reduced F A F B , is the direct electron donor to the Flv1/Flv3 heterodimer. Evidences for large reduction of (F A F B) and recombination reactions within PSI were also provided by near-infrared absorption. Mutants lacking either the NDH1-L complex, the homolog of complex I of respiration, or the Pgr5 protein show no difference with WT in the oxidation of reduced FeS following a short illumination. These observations question the participation of a significant cyclic electron flow in cyanobacteria during the first seconds of the induction phase of photosynthesis.
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Dates et versions

hal-03032490 , version 1 (30-11-2020)

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Pierre Sétif, Ginga Shimakawa, Anja Krieger-Liszkay, Chikahiro Miyake. Identification of the electron donor to flavodiiron proteins in Synechocystis sp. PCC 6803 by in vivo spectroscopy. Biochimica biophysica acta (BBA) - Bioenergetics, 2020, 1861 (10), pp.148256. ⟨10.1016/j.bbabio.2020.148256⟩. ⟨hal-03032490⟩
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