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首页> 外文期刊>Journal of Molecular Biology >The crystal structure of a sulfurtransferase from Azotobacter vinelandii highlights the evolutionary relationship between the rhodanese and phosphatase enzyme families.
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The crystal structure of a sulfurtransferase from Azotobacter vinelandii highlights the evolutionary relationship between the rhodanese and phosphatase enzyme families.

机译：来自葡萄固氮菌的硫转移酶的晶体结构突出了罗丹色和磷酸酶家族之间的进化关系。

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摘要

Rhodanese is an ubiquitous enzyme that in vitro catalyses the transfer of a sulfur atom from suitable donors to nucleophilic acceptors by way of a double displacement mechanism. During the catalytic process the enzyme cycles between a sulfur-free and a persulfide-containing form, via formation of a persulfide linkage to a catalytic Cys residue. In the nitrogen-fixing bacteria Azotobacter vinelandii the rhdA gene has been identified and the encoded protein functionally characterized as a rhodanese. The crystal structure of the A. vinelandii rhodanese has been determined and refined at 1.8 A resolution in the sulfur-free and persulfide-containing forms. Conservation of the overall three-dimensional fold of bovine rhodanese is observed, with substantial modifications of the protein structure in the proximity of the catalytic residue Cys230. Remarkably, the native enzyme is found as the Cys230-persulfide form; in the sulfur-free state the catalytic Cys residue adopts two alternate conformations, reflected by perturbation of the neighboring active-site residues, which is associated with a partly reversible loss of thiosulfate:cyanide sulfurtransferase activity. The catalytic mechanism of A. vinelandii rhodanese relies primarily on the main-chain conformation of the 230 to 235 active-site loop and on a surrounding strong positive electrostatic field. Substrate recognition is based on residues which are entirely different in the prokaryotic and eukaryotic enzymes. The active-site loop of A. vinelandii rhodanese displays striking structural similarity to the active-site loop of the similarly folded catalytic domain of dual specific phosphatase Cdc25, suggesting a common evolutionary origin of the two enzyme families. Copyright 2000 Academic Press.
机译：Rhodanese是一种普遍存在的酶，它通过双重置换机制在体外催化硫原子从合适的供体向亲核受体的转移。在催化过程中，酶通过形成与催化Cys残基的过硫键，在无硫和含过硫的形式之间循环。在固氮细菌葡萄固氮菌中，rhdA基因已被鉴定，编码的蛋白质在功能上被表征为罗丹色。已经确定了无花果硫和含过硫化物形式的葡萄球菌罗丹果的晶体结构，并以1.8 A的分辨率进行了精制。观察到牛Rhodanese的整体三维折叠的保守性，在催化残基Cys230附近蛋白质结构发生了实质性改变。值得注意的是，天然酶以Cys230-过硫化物的形式存在。在无硫状态下，催化的Cys残基采用两个交替的构象，反映在邻近的活性位点残基的扰动上，这与硫代硫酸盐：氰化物硫转移酶活性的部分可逆损失有关。葡萄球菌Rhodandanese的催化机理主要取决于230至235个活性位点环的主链构象和周围的强正静电场。底物识别基于在原核和真核酶中完全不同的残基。葡萄球菌的活性位点环与双特异性磷酸酶Cdc25相似折叠的催化结构域的活性位点环具有惊人的结构相似性，表明这两个酶家族具有共同的进化起源。版权所有2000学术出版社。

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