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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Study of the high-potential iron sulfur protein in Halorhodospira halophila confirms that it is distinct from cytochrome c as electron carrier
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Study of the high-potential iron sulfur protein in Halorhodospira halophila confirms that it is distinct from cytochrome c as electron carrier

机译：对嗜盐嗜盐螺旋藻中高潜力的铁硫蛋白的研究证实，它不同于作为电子载体的细胞色素c

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摘要

The role of high-potential iron sulfur protein (HiPIP) in donating electrons to the photosynthetic reaction center in the halophilic γ-proteobacterium Halorhodospira halophila was studied by EPR and time-resolved optical spectroscopy. A tight complex between HiPIP and the reaction center was observed. The EPR spectrum of HiPIP in this complex was drastically different from that of the purified protein and provides an analytical tool for the detection and characterization of the complexed form in samples ranging from whole cells to partially purified protein. The bound HiPIP was identified as iso-HiPIP Ⅱ. Its E_m value at pH 7 in the form bound to the reaction center was ≈100 mV higher (+ 140 ± 20 mV) than that of the purified protein. EPR on oriented samples showed HiPIP Ⅱ to be bound in a well defined geometry, indicating the presence of specific protein-protein interactions at the docking site. At moderately reducing conditions, the bound HiPIP Ⅱ donates electrons to the cytochrome subunit bound to the reaction center with a half-time of ≤ 11 μs. This donation reaction was analyzed by using Marcus's outer-sphere electron-transfer theory and compared with those observed in other HiPIP-containing purple bacteria. The results indicate substantial differences between the HiPIP- and the cytochrome c_2-mediated re-reduction of the reaction center.
机译：通过EPR和时间分辨光谱法研究了高电位铁硫蛋白（HiPIP）在将电子提供给嗜盐γ-变形杆菌Halohodospira halophila的光合作用反应中心中的作用。观察到HiPIP和反应中心之间的紧密配合。该复合物中HiPIP的EPR谱图与纯化蛋白的谱图完全不同，并为分析和表征从全细胞到部分纯化蛋白的样品中的复合物形式提供了一种分析工具。结合的HiPIP被鉴定为iso-HiPIPⅡ。在pH 7时以结合到反应中心的形式的E_m值比纯化的蛋白质高约100 mV（+ 140±20 mV）。定向样品上的EPR显示，HiPIPⅡ以明确定义的几何形状结合，表明在对接位点存在特定的蛋白质-蛋白质相互作用。在中等还原条件下，结合的HiPIPⅡ以半衰期≤11μs将电子提供给与反应中心结合的细胞色素亚基。使用马库斯（Marcus）的外层电子转移理论分析了该捐赠反应，并将其与其他含有HiPIP的紫色细菌中观察到的捐赠反应进行了比较。结果表明，HiPIP-和细胞色素c_2介导的反应中心还原之间存在显着差异。

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