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首页> 外文期刊>Acta crystallographica.Section D. Biological crystallography >The structure of carbamoyl phosphate synthetase determined to 2.1 A resolution.
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The structure of carbamoyl phosphate synthetase determined to 2.1 A resolution.

机译：[氨基甲酰磷酸合成酶的结构2.1决定决议。

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摘要

Carbamoyl phosphate synthetase catalyzes the formation of carbamoyl phosphate from one molecule of bicarbonate, two molecules of Mg2+ATP and one molecule of glutamine or ammonia depending upon the particular form of the enzyme under investigation. As isolated from Escherichia coli, the enzyme is an alpha,beta-heterodimer consisting of a small subunit that hydrolyzes glutamine and a large subunit that catalyzes the two required phosphorylation events. Here the three-dimensional structure of carbamoyl phosphate synthetase from E. coli refined to 2.1 A resolution with an R factor of 17.9% is described. The small subunit is distinctly bilobal with a catalytic triad (Cys269, His353 and Glu355) situated between the two structural domains. As observed in those enzymes belonging to the alpha/beta-hydrolase family, the active-site nucleophile, Cys269, is perched at the top of a tight turn. The large subunit consists of four structural units: the carboxyphosphate synthetic component, the oligomerization domain, the carbamoyl phosphate synthetic component and the allosteric domain. Both the carboxyphosphate and carbamoyl phosphate synthetic components bind Mn2+ADP. In the carboxyphosphate synthetic component, the two observed Mn2+ ions are both octahedrally coordinated by oxygen-containing ligands and are bridged by the carboxylate side chain of Glu299. Glu215 plays a key allosteric role by coordinating to the physiologically important potassium ion and hydrogen bonding to the ribose hydroxyl groups of ADP. In the carbamoyl phosphate synthetic component, the single observed Mn2+ ion is also octahedrally coordinated by oxygen-containing ligands and Glu761 plays a similar role to that of Glu215. The carboxyphosphate and carbamoyl phosphate synthetic components, while topologically equivalent, are structurally different, as would be expected in light of their separate biochemical functions.
机译：[氨基甲酰磷酸合成酶催化从一个形成[氨基甲酰磷酸碳酸氢分子,两个分子Mg2 + ATP和一个分子谷氨酰胺或氨这取决于酶的特殊形式在调查之中。杆菌,这种酶是一种α,beta-heterodimer小亚基组成的水解谷氨酰胺和一个大亚基的催化两个必需的磷酸化的事件。三维结构的[氨基甲酰2.1从大肠杆菌精制磷酸合成酶一项决议的R因子是17.9%描述。bilobal催化三分子(Cys269 His353和Glu355)坐落在两个结构之间域。α/ beta-hydrolase家庭,活性部位亲核试剂,Cys269坐在急转弯。由四个结构单位:carboxyphosphate合成组件[氨基甲酰磷酸寡聚化域合成组件和变构域。carboxyphosphate和[氨基甲酰磷酸合成组件绑定Mn2 + ADP。carboxyphosphate合成组件,这两个概念观察Mn2 +离子都是八面体的通过含氧配体,并进行协调桥接的羧酸盐Glu299的侧链。Glu215扮演了一个关键的变构作用生理上重要的协调钾离子和氢键核糖ADP的羟基。磷酸合成组件,单身观察Mn2 +离子也是八面体的含氧配体和协调Glu761 Glu215的扮演类似的角色。carboxyphosphate和[氨基甲酰磷酸合成组件,而拓扑等效结构不同,会根据他们的分离生化功能。

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