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首页> 外文期刊>Biochemistry >High-Resolution X-Ray Structure of Isoaspartyl Dipeptidase from Escherichia coli(,).
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High-Resolution X-Ray Structure of Isoaspartyl Dipeptidase from Escherichia coli(,).

机译：来自大肠杆菌（，）的Isoaspartyl二肽酶的高分辨率X射线结构。

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Isoaspartyl dipeptidase from Escherichia coli functions in protein degradation by catalyzing the hydrolysis of beta-l-isoaspartyl linkages in dipeptides. The best substrate for the enzyme reported thus far is iso-Asp-Leu. Here we report the X-ray analysis of the enzyme in its resting state and complexed with aspartate to 1.65 and 2.1 A resolution, respectively. The quaternary structure of the enzyme is octameric and can be aptly described as a tetramer of dimers. Each subunit folds into two distinct domains: the N-terminal region containing eight strands of mixed beta-sheet and the C-terminal motif that is dominated by a (beta,alpha)(8)-barrel. A binuclear zinc center is located in each subunit at the C-terminal end of the (beta,alpha)(8)-barrel. Ligands to the binuclear metal center include His 68, His 70, His 201, His 230, and Asp 285. The two zincs are bridged by a carboxylated lysine residue (Lys 162) and a solvent molecule, most likely a hydroxide ion. The product of the reaction, aspartate, bindsto the enzyme by displacing the bridging solvent with its side chain functional group. From this investigation it is proposed that the reaction mechanism of the enzyme proceeds through a tetrahedral intermediate and that the bridging solvent attacks the re face of the carbonyl carbon of the scissile peptide bond. This structural analysis confirms the placement of isoaspartyl dipeptidase into the urease-related amidohydrolase superfamily.
机译：通过催化二肽中的β-L-异淀粉键的水解，来自大肠杆菌基氨基磷酶在蛋白质降解中的作用。迄今为止报道的酶的最佳底物是ISO-ASP-Leu。在这里，我们在其静止状态下报告酶的X射线分析，并分别用天冬氨酸复合为1.65和2.1分辨率。酶的季铵结构是八大数，可以恰当地描述为二聚体的四聚体。每个亚基折叠成两个不同的结构域：包含八个混合β-片和由（β，α）（8）-barrel支配的C末端基序的N-末端区域。 Binuclear锌中心位于（β，α）（8）-barrel的C-末端的每个亚基中。双核金属中心的配体包括他的68，他的70，他的201，他的2013,230和ASP 285.这两个锌由羧化赖氨酸残基（Lys 162）和溶剂分子桥接，最可能是氢氧化离子。通过用侧链官能团移位桥接溶剂，反应的产物，天冬氨酸，结合酶。从该研究中提出，酶的反应机理通过四面体中间体进行，并且桥接溶剂攻击透析肽键的羰基碳的再面对。该结构分析证实了Isoaspartyl二肽酶的放置在脲酶相关的氨基羟氨水解酶超家族中。

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