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N_2O binding at a [4Cu:2S] copper-sulphur cluster in nitrous oxide reductase

机译：N_2O在一氧化二氮还原酶中[4Cu：2S]铜-硫簇上的结合

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摘要

Nitrous oxide (N_2O) is generated by natural and anthropogenic processes and has a critical role in environmental chemistry. It has an ozone-depleting potential similar to that of hydrochlorofiuorocar-bons as well as a global warming potential exceeding that of CO_2 300-fold1-2. In bacterial denitrification, N_2O is reduced to N_2 by the copper-dependent nitrous oxide reductase (N_2OR)~3. This enzyme carries the mixed-valent Cu_A centre and the unique, tetranudear Cu_z site. Previous structural data were obtained with enzyme isolated in the presence of air that is catalytically inactive without prior reduction. Its Cu_z site was described as a [4Cu:S] centre, and the substrate-binding mode and reduction mechanism remained elusive. Here we report the structure of purple N_2OR from Pseudomonas stutzeri, handled under the exclusion of dioxygen, and locate the substrate in N_2O-pressurized crystals. The active Cu_z cluster contains two sulphur atoms, yielding a [4Cu:2S] stoichiometry; and N_2O bound side-on at Cu_z, in close proximity to Cu_A. With the substrate located between the two clusters, electrons are transferred directly from Cu_A to N_2O, which is activated by side-on binding in a specific binding pocket on the face of the [4Cu:2S] centre. These results reconcile a multitude of available biochemical data on N_2OR that could not be explained by earlier structures, and outline a mechanistic pathway in which both metal centres and the intervening protein act in concert to achieve catalysis. This structure represents the first direct observation, to our knowledge, of N_2O bound to its reductase, and sheds light on the functionality of metalloenzymes that activate inert small-molecule substrates. The principle of using distinct clusters for substrate activation and for reduction may be relevant for similar systems, in particular nitrogen-fixing nitrogenase4.
机译：一氧化二氮（N_2O）是由自然和人为过程产生的，在环境化学中具有关键作用。它具有与氢氯氟碳类似的臭氧消耗潜能，并且其全球变暖潜能超过CO_2 300-1-2。在细菌的反硝化中，N_2O被铜依赖性的一氧化二氮还原酶（N_2OR）〜3还原为N_2。该酶带有混合价的Cu_A中心和独特的四核Cu_z位点。先前的结构数据是通过在空气中分离的酶获得的，该空气是催化惰性的，无需事先还原。它的Cu_z位点被描述为[4Cu：S]中心，并且底物结合模式和还原机理仍然难以捉摸。在这里，我们报告斯图氏假单胞菌紫色N_2OR的结构，在排除双氧的情况下进行处理，并将底物置于N_2O加压的晶体中。活性Cu_z团簇包含两个硫原子，化学计量比为[4Cu：2S]。和N_2O在Cu_z上并排结合，非常靠近Cu_A。衬底位于两个簇之间，电子直接从Cu_A转移到N_2O，后者通过[4Cu：2S]中心面上特定结合口袋中的侧面结合而被激活。这些结果调和了许多有关N_2OR的可用生化数据，而早期的结构无法解释这些数据，并概述了一种机制途径，其中金属中心和中间蛋白共同起作用以实现催化作用。据我们所知，这种结构代表了对与其还原酶结合的N_2O的首次直接观察，并揭示了激活惰性小分子底物的金属酶的功能。使用不同簇进行底物活化和还原的原理可能与类似系统有关，尤其是固氮固氮酶4。

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  • 来源
    《Nature》 |2011年第7363期|p.234-237|共4页
  • 作者

    Anja Pomowski; Walter G. Zumft; Peter M. H. Kroneck; Oliver Enisle;

  • 作者单位

    Lehrstuht fur Biochemie, Institut fur organische Chemie und Biochemie, Albert-Ludwigs-Universitat Freiburg, Albertstr. 21, 79104 Freiburg, Germany;

    Institut fur Angewandte Biowissenschaften,Abteilung Molekulare Mikrobiologie, Karisruher Institut fCir Technologie, Hertzstr. 16, 76187 Karlsruhe, Germany;

    Fachbereich Biologie, Universitat Konstanz, Universitatsstr. 10, 78457 Konstanz,Germany;

    Lehrstuht fur Biochemie, Institut fur organische Chemie und Biochemie, Albert-Ludwigs-Universitat Freiburg, Albertstr. 21, 79104 Freiburg, Germany Centre for Biological Signalling Studies (bioss), Albert-Ludwigs-Universitat Freiburg, Hebelstr. 25, 79104 Freiburg, Germany;

  • 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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