OROTATE PHOSPHORIBOSYLTRANSFERASE--MECHANISM

描述：核苷一磷酸合成提供以下成分 DNA、RNA、ATP和NAD，需要磷酸核糖基转移酶的作用 (PRTase)将核糖5-磷酸基团从其供体PRPP转移到 特定的杂环碱。PRTase是几个 威胁生命的遗传性疾病，是 抗寄生虫、抗微生物和抗肿瘤药物。该财团寻求 了解PRTase酶群的结构和功能。 ORotate PRTase、次黄嘌呤-鸟嘌呤PRTase和喹啉酸PRTase已被 结晶并测定了它们的三维结构。该项目 旨在揭示酶催化的结构和化学细节 通过对OPRTase和QAPRTase的研究。使用化学淬火技术， 将详细介绍OPRTase动力学机制，以便了解 新发现的结合和催化的负协同效应。这个 OPRTase Active Site与亚基接口相邻，需要移动设备 邻近亚基贡献的蛋白质结构元件(环)。 亚基界面上的结构相互作用可能负责 协作性。柔性分子对活性中心化学的贡献 元素将使用点突变和部分循环删除来确定 并通过测定与新型合成化合物络合的酶的结构 双底物类似物抑制剂。一对分子的催化作用 将测定1类PRTase常见的羧酸残基。 QAPRTase代表了一个新发现的进化起源和小说 PRTase组的结构(第2类PRTase折叠)。这个 X射线对QAPRT酶结构的细化和催化活性的作用 将测定结构上与OPRTase相似的位点残基。

DESCRIPTION: Nucleoside monophosphate synthesis provides the components of DNA, RNA, ATP and NAD and requires the action of phosphoribosyltransferases (PRTases) to transfer the ribose 5-phosphate group from its donor PRPP to specific heterocyclic bases. The PRTases are the site of several life-threatening hereditary disorders, and are legitimate targets for anti-parasitic, anti-microbial and anti-tumor agents. This consortium seeks to understand the structure and function of the PRTase enzyme group. Orotate PRTase, hypoxanthine-guanine PRTase and quinolinate PRTase have been crystallized and their three dimensional structures determined. The project seeks to reveal the structural and chemical details of enzymic catalysis through studies of OPRTase and QAPRTase. Using chemical quench techniques, the OPRTase kinetic mechanism will be detailed to permit understanding of newly discovered negative cooperativity of binding and catalysis. The OPRTase active site borders the subunit interface, and requires a mobile protein structural element (loop) contributed by the adjacent subunit. Structural interactions at the subunit interface may be responsible for cooperativity. The contribution to active site chemistry of the flexible element will be determined using point mutants and partial loop deletants and by determining the structure of enzyme complexed with novel synthetic bi-substrate analogue inhibitors. The catalytic function of a pair of carboxylate residues, common to Class 1 PRTases, will be determined. QAPRTase represents a newly discovered evolutionary origin and novel architecture (the Class 2 PRTase fold) for the PRTase enzyme group. The X-ray structure of QAPRTase will be refined and the catalytic role of active site residues structurally analogous to those in OPRTase will be determined.