STRUCTURAL STUDIES OF METAL-BINDING BY INOSITOL MONOPHOSPHATASE - EVIDENCE FOR 2-METAL ION CATALYSIS
STRUCTURAL STUDIES OF METAL-BINDING BY INOSITOL MONOPHOSPHATASE - EVIDENCE FOR 2-METAL ION CATALYSIS
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DOI：
10.1021/bi00198a012
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发表时间：
1994-08-16
期刊：
影响因子：
2.9
通讯作者：
ATACK, JR
中科院分区：
文献类型：
--
作者：
BONE, R;FRANK, L;ATACK, JR
测定了肌醇单磷酸酶在与Mn2+和Mn2+与磷酸盐配合物中的结构为2.60埃分辨率。在Mn2+配合物中，三个金属阳离子和一个Cl-结合在酶的两个亚基上的活性位点上。这三种金属的配体包括Glu 70、Asp 90、Asp 93和Asp 220的侧链、Ile 92的羰基、几种溶剂分子，以及作为每个阳离子的配体的氯化物。当磷酸盐浸泡在这些Mn2+共晶体中时，三个Mn2+离子中的一个被从活性位点排出，留下具有八面体和四面体配位几何的金属离子。此外，在2.5埃的分辨率下测定了脂肪醇单磷酸酶的结构。残基70-75是一个参与金属配位的两转螺旋片段，在没有阳离子的情况下，它从金属结合位点移动了2-3埃。残基30-40包裹在金属结合位点周围，通过溶剂分子和与金属的蛋白质配体间接与金属相互作用，在没有金属的情况下变得无序。在各种金属配合物中，在形成金属结合位点的残基中也观察到节段迁移性。这些肌醇单磷酸酶与阳离子相互作用的研究结果表明，该酶使用两种金属离子完成磷酸酯水解，一种是八面体配位几何，另一种是四面体配位几何。广泛的金属结合特异性似乎是由于提供金属配体的几个蛋白质片段具有广泛的灵活性，来自替代金属配体的存在以及包括水分子的金属配位球。
The structure of inositol monophosphatase has been determined to 2.60 Angstrom resolution in complexes with Mn2+ and with Mn2+ and phosphate. In the Mn2+ complex, three metal cations and one Cl- were bound in the active site on each of the two subunits of the enzyme. Ligands to the three metals include the side chains of Glu 70, Asp 90, Asp 93, and Asp 220, the carbonyl group of Ile 92, several solvent molecules, and the chloride, which is a ligand to each of the cations. When phosphate is soaked into these Mn2+ cocrystals, one of the three Mn2+ ions is expelled from the active site, leaving metal ions with octahedral and tetrahedral coordination geometry. In addition, the structure of apoinositol monophosphatase was determined to 2.5 Angstrom resolution. Residues 70-75, a two-turn helical segment which is involved in metal coordination, moves away from the metal binding site by 2-3 Angstrom in the absence of cations. Residues 30-40, which wrap around the metal binding site and interact with the metal indirectly through solvent molecules and protein ligands to the metal, become disordered in the absence of metal. In various metal complexes, segmental mobility is also observed in the residues which form the metal binding sites. The results of these studies of the interaction of inositol monophosphatase with cations suggest that the enzyme accomplishes phosphate ester hydrolysis using two metal ions, one with octahedral and one with tetrahedral coordination geometry. Broad metal-binding specificity appears to result from extensive flexibility in several of the protein segments which contribute metal ligands, from the presence of alternate metal ligands and from metal coordination spheres which include water molecules.