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Control of substrate access to the active site in methane monooxygenase

机译：控制底物对甲烷单加氧酶中活性位点的访问

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摘要

Methanotrophs consume methane as their major carbon source and have an essential role in the global carbon cycle by limiting escape of this greenhouse gas to the atmosphere. These bacteria oxidize methane to methanol by soluble and particulate methane mono-oxygenases (MMOs). Soluble MMO contains three protein components, a 251-kilodalton hydroxylase (MMOH), a 38.6-kilodalton reductase (MMOR), and a 15.9-kilodalton regulatory protein (MMOB), required to couple electron consumption with substrate hydroxylation at the catalytic diiron centre of MMOH. Until now, the role of MMOB has remained ambiguous owing to a lack of atomic-level information about the MMOH-MMOB (hereafter termed H-B) complex. Here we remedy this deficiency by providing a crystal structure of H-B, which reveals the manner by which MMOB controls the conformation of residues in MMOH crucial for substrate access to the active site. MMOB docks at the α_2β_2 interface of α_2β_2γ_2 MMOH, and triggers simultaneous conforma-tional changes in the α-subunit that modulate oxygen and methane access as well as proton delivery to the diiron centre. Without such careful control by MMOB of these substrate routes to the diiron active site, the enzyme operates as an NADH oxidase rather than a monooxygenase. Biological catalysis involving small substrates is often accomplished in nature by large proteins and protein complexes. The structure presented in this work provides an elegant example of this principle.
机译：甲烷营养生物消耗甲烷作为其主要碳源，并且通过限制这种温室气体向大气中的逸出，在全球碳循环中发挥着重要作用。这些细菌通过可溶性和颗粒状甲烷单加氧酶（MMO）将甲烷氧化为甲醇。可溶性MMO包含三种蛋白质成分，分别是电子消耗与底物的催化二铁中心的羟基化作用耦合在一起所需的蛋白质，其中一个是251钾盐羟化酶（MMOH），一个38.6钾盐还原酶（MMOR）和一个15.9钾盐调节蛋白（MMOB）。 MMOH。到目前为止，由于缺乏有关MMOH-MMOB（以下称为H-B）配合物的原子级信息，MMOB的作用一直是模棱两可的。在这里，我们通过提供H-B的晶体结构来纠正这种缺陷，该结构揭示了MMOB控制MMOH中对底物进入活性位点至关重要的残基构象的方式。 MMOB停靠在α_2β_2γ_2MMOH的α_2β_2界面处，并同时触发α亚基的构象变化，从而调节氧气和甲烷的进入以及质子向二铁中心的传递。在没有通过MMOB仔细控制这些底物途径到达二铁活性位点的情况下，该酶作为NADH氧化酶而不是单加氧酶起作用。涉及小底物的生物催化通常在自然界中通过大蛋白质和蛋白质复合物来完成。本工作中介绍的结构为该原理提供了一个优雅的例子。

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  • 来源
    《Nature》 |2013年第7437期|380-384|共5页
  • 作者

    Seung Jae Lee; Michael S. McCormick; Stephen J. Lippard; Uhn-Soo Cho;

  • 作者单位

    Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA;

    Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA;

    Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA;

    Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, 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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