Lesniak Jacob, Barton William A, Nikolov Dimitar B
Joan and Sanford I.Weill Graduate School of Medical Sciences of Cornell University, New York City, NY 10021, USA.
EMBO J. 2002 Dec 16;21(24):6649-59. doi: 10.1093/emboj/cdf670.
Bacteria have developed complex strategies to detoxify and repair damage caused by reactive oxygen species. These compounds, produced during bacterial aerobic respiration as well as by the host immune system cells as a defense mechanism against the pathogenic microorganisms, have the ability to damage nucleic acids, proteins and phospholipid membranes. Here we describe the crystal structure of Pseudomonas aeruginosa Ohr, a member of a recently discovered family of organic hydroperoxide resistance proteins. Ohr is a tightly folded homodimer, with a novel alpha/beta fold, and contains two active sites located at the monomer interface on opposite sides of the molecule. Using in vitro assays, we demonstrate that Ohr functions directly as a hydroperoxide reductase, converting both inorganic and organic hydroperoxides to less toxic metabolites. Site-directed mutagenesis confirms that the two conserved cysteines in each active site are essential for catalytic activity. We propose that the Ohr catalytic mechanism is similar to that of the structurally unrelated peroxiredoxins, directly utilizing highly reactive cysteine thiol groups to elicit hydroperoxide reduction.
细菌已经发展出复杂的策略来解毒和修复由活性氧引起的损伤。这些化合物在细菌有氧呼吸过程中产生，同时也是宿主免疫系统细胞作为抵御病原微生物的防御机制而产生的，它们能够损伤核酸、蛋白质和磷脂膜。在这里，我们描述了铜绿假单胞菌Ohr的晶体结构，它是最近发现的有机氢过氧化物抗性蛋白家族的一员。Ohr是一种紧密折叠的同型二聚体，具有新颖的α/β折叠，并且在分子相对两侧的单体界面处含有两个活性位点。通过体外试验，我们证明Ohr直接作为氢过氧化物还原酶发挥作用，将无机和有机氢过氧化物转化为毒性较小的代谢产物。定点诱变证实每个活性位点中的两个保守半胱氨酸对于催化活性至关重要。我们提出，Ohr的催化机制与结构不相关的过氧化物酶相似，直接利用高反应性的半胱氨酸硫醇基团引发氢过氧化物的还原。
