Identification of the electron donor to flavodiiron proteins in Synechocystis sp. PCC 6803 by in vivo spectroscopy
Identification of the electron donor to flavodiiron proteins in Synechocystis sp. PCC 6803 by in vivo spectroscopy
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DOI：
10.1016/j.bbabio.2020.148256
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发表时间：
2020-10-01
影响因子：
4.3
通讯作者：
Miyake, Chikahiro
中科院分区：
文献类型：
--
作者：
Setif, Pierre;Shimakawa, Ginga;Miyake, Chikahiro
光合生物的黄酮二铁蛋白（FDP）通过将氧还原为水从而避免在胁迫条件下过量电子在光系统I（PSI）受体侧的积累而发挥光保护作用。在高CO2条件下生长的集胞藻6803中，FDP Flv 1和Flv 3都是氧还原所必需的。我们进行了详细的体内动力学研究野生型（WT）和Delta flv 1/3菌株的集胞藻使用光诱导的NADPH荧光和近红外吸收的铁硫簇铁氧还蛋白和PSI受体（FAFB），统称为FeS。这些测量是在Calvin-Benson循环不活跃或活化不良的条件下进行的。在这样的条件下，NADPH衰减后，一个短的照明衰减在两个菌株中平行，并表现出与还原FeS的存在相关的时间滞后。相反，WT中还原态FeS的衰变速度比Delta flv 13中快得多（13 vs 2 s（-1））。这些数据明确地表明，还原的铁氧还蛋白，或可能还原的FAFB，是Flv 1/Flv 3异二聚体的直接电子供体。近红外吸收也提供了PSI内（FAFB）和重组反应的大量减少的证据。突变体缺乏NDH 1-L复合物，同源物的复合物I的呼吸，或Pgr 5蛋白显示没有差异与野生型在氧化还原FeS短光照后。这些意见的问题，在光合作用的诱导阶段的第一秒，在蓝藻中的一个显着的循环电子流的参与。
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 CO2, both FDPs Flv1 and Flv3 are indispensable for oxygen reduction. We performed a detailed in vivo kinetic study of wild-type (WT) and Delta flv1/3 strains of Synechocystis using light-induced NADPH fluorescence and near-infrared absorption of iron-sulfur clusters from ferredoxin and the PSI acceptors (FAFB), 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 Delta flv1/3 (13 vs 2 s(-1)). These data unambiguously show that reduced ferredoxin, or possibly reduced FAFB, is the direct electron donor to the Flv1/Flv3 heterodimer. Evidences for large reduction of (FAFB) 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.