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Structure of the complex Ⅰ-like molecule NDH of oxygenic photosynthesis

机译：氧合作用的Ⅰ类复合分子NDH的结构

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摘要

Cyclic electron flow around photosystem I (PSI) is a mechanism by which photosynthetic organisms balance the levels of ATP and NADPH necessary for efficient photosynthesis(1,2). NAD(P)H dehydrogenase-like complex (NDH) is a key component of this pathway in most oxygenic photosynthetic organisms(3,4) and is the last large photosynthetic membrane-protein complex for which the structure remains unknown. Related to the respiratory NADH dehydrogenase complex (complex I), NDH transfers electrons originating from PSI to the plastoquinone pool while pumping protons across the thylakoid membrane, thereby increasing the amount of ATP produced per NADP+ molecule reduced(4,5). NDH possesses 11 of the 14 core complex I subunits, as well as several oxygenic-photosynthesis-specific (OPS) subunits that are conserved from cyanobacteria to plants(3,6). However, the three core complex I subunits that are involved in accepting electrons from NAD(P) H are notably absent in NDH3,5,6, and it is therefore not clear how NDH acquires and transfers electrons to plastoquinone. It is proposed that the OPS subunits-specifically NdhS-enable NDH to accept electrons from its electron donor, ferredoxin(3-5,7). Here we report a 3.1 angstrom structure of the 0.42-MDa NDH complex from the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1, obtained by single-particle cryo-electron microscopy. Our maps reveal the structure and arrangement of the principal OPS subunits in the NDH complex, as well as an unexpected cofactor close to the plastoquinone-binding site in the peripheral arm. The location of the OPS subunits supports a role in electron transfer and defines two potential ferredoxin-binding sites at the apex of the peripheral arm. These results suggest that NDH could possess several electron transfer routes, which would serve to maximize plastoquinone reduction and avoid deleterious off-target chemistry of the semi-plastoquinone radical.
机译：围绕光系统I（PSI）的循环电子流是一种机制，光合生物通过该机制平衡有效光合作用所需的ATP和NADPH的水平（1,2）。 NAD（P）H脱氢酶样复合物（NDH）是大多数含氧光合生物中该途径的关键组成部分（3,4），并且是最后一个结构未知的大型光合膜-蛋白质复合物。与呼吸NADH脱氢酶复合物（复合物I）有关，NDH将质子泵送通过质体膜的同时将源自PSI的电子转移到质体醌库中，从而增加了每个NADP +分子减少时产生的ATP量（4,5）。 NDH拥有14个核心复合物I亚基中的11个，以及几个从蓝细菌保守到植物的氧合光合作用特异性（OPS）亚基（3,6）。但是，在NDH3、5、6中不存在参与接受来自NAD（P）H的电子的三个核心复合物I亚基，因此尚不清楚NDH如何获取电子并将其转移至质体醌。有人提出，OPS亚基可以特异性地使NdhS激活NDH接受来自其电子供体铁氧还蛋白（3-5,7）的电子。在这里，我们报告了从嗜热蓝藻嗜热嗜热球菌BP-1，通过单粒子冷冻电子显微镜获得的0.42-MDa NDH复合物的3.1埃结构。我们的图谱揭示了NDH复合物中主要OPS亚基的结构和排列，以及靠近外周臂中质体醌结合位点的意外辅因子。 OPS亚基的位置在电子转移中发挥作用，并在外周臂的顶点处定义了两个潜在的铁氧还蛋白结合位点。这些结果表明，NDH可能具有几种电子转移途径，这将最大限度地减少质体醌还原，并避免半质体醌自由基的有害脱靶化学反应。

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  • 来源
    《Nature》 |2019年第7744期|411-414|共4页
  • 作者

    Laughlin Thomas G.; Bayne Andrew N.; Trempe Jean-Francois; Savage David F.; Davies Karen M.;

  • 作者单位

    Univ Calif Berkeley, Dept Mol & Cell Biol, 229 Stanley Hall, Berkeley, CA 94720 USA|Lawrence Berkeley Natl Lab, Mol Biophys & Integrat Bioimaging Div, Berkeley, CA 94720 USA;

    Grp Etud Proteines Membranaires GEPROM, Montreal, PQ, Canada|McGill Univ, Dept Pharmacol & Therapeut, Montreal, PQ, Canada;

    Grp Etud Proteines Membranaires GEPROM, Montreal, PQ, Canada|McGill Univ, Dept Pharmacol & Therapeut, Montreal, PQ, Canada;

    Univ Calif Berkeley, Dept Mol & Cell Biol, 229 Stanley Hall, Berkeley, CA 94720 USA;

    Univ Calif Berkeley, Dept Mol & Cell Biol, 229 Stanley Hall, Berkeley, CA 94720 USA|Lawrence Berkeley Natl Lab, Mol Biophys & Integrat Bioimaging Div, Berkeley, CA 94720 USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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