Crystal structure of methyl parathion hydrolase from Pseudomonas sp WBC-3
Crystal structure of methyl parathion hydrolase from Pseudomonas sp WBC-3
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DOI：
10.1016/j.jmb.2005.08.057
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发表时间：
2005-10-28
影响因子：
5.6
通讯作者：
Zhang, XE
中科院分区：
文献类型：
--
作者：
Dong, YJ;Bartlam, M;Zhang, XE
甲基对硫磷水解酶（MPH，E.C.3.1.8.1），从土壤细菌假单胞菌中分离出来。 WBC-3 是一种含 Zn(II) 的酶，可催化有机磷农药甲基对硫磷的降解。我们已经确定了假单胞菌 MPH 的结构。 WBC-3 至 2.4 埃分辨率。该酶是二聚体，每个亚基都包含一个混合杂合双核锌中心，其中一个锌离子被镉取代。在这两个亚基中，由于结晶条件下镉浓度较高，更多暴露于溶剂的 β-金属离子被 Cd2+ 取代。两种离子都被八面体排列的配体包围。这些离子相距 3.5 埃，并由氨基酸残基 His147、His149、Asp151、His152、His234 和 His302 以及水分子配位。 Asp255 和水分子将锌离子桥接在一起。 MPH 与其他金属-β-内酰胺酶同源，但与磷酸三酯酶没有任何相似性，磷酸三酯酶也能以较低的速率催化甲基对硫磷的降解，尽管缺乏序列同源性。 Trp179、Phe196 和 Phe119 在催化中心入口处形成芳香族簇。用丙氨酸取代这三个氨基酸导致 Km 显着增加并丧失催化活性，表明芳香族簇在促进酶与甲基对硫磷底物的亲和力方面具有重要作用。 (c) 2005 Elsevier Ltd. 保留所有权利。
Methyl parathion hydrolase (MPH, E.C.3.1.8.1), isolated from the soil-dwelling bacterium Pseudomonas sp. WBC-3, is a Zn(II)-containing enzyme that catalyzes the degradation of the organophosphate pesticide methyl parathion. We have determined the structure of MPH from Pseudomonas sp. WBC-3 to 2.4 angstrom resolution. The enzyme is dimeric and each subunit contains a mixed hybrid binuclear zinc center, in which one of the zinc ions is replaced by cadmium. In both subunits, the more solvent-exposed beta-metal ion is substituted for Cd2+ due to high cadmium concentration in the crystallization condition. Both ions are surrounded by ligands in an octahedral arrangement. The ions are separated by 3.5 angstrom and are coordinated by the amino acid residues His147, His149, Asp151, His152, His234 and His302 and a water molecule. Asp255 and a water molecule serve to bridge the zinc ions together. MPH is homologous with other metallo-beta-lactamases but does not show any similarity to phosphotriesterase that can also catalyze the degradation of methyl parathion with lower rate, despite the lack of sequence homology. Trp179, Phe196 and Phe119 form an aromatic cluster at the entrance of the catalytic center. Replacement of these three amino acids by alanine resulted in a significant increase of Km and loss of catalytic activity, indicating that the aromatic cluster has an important role to facilitate affinity of enzyme to the methyl parathion substrates. (c) 2005 Elsevier Ltd. All rights reserved.