OROTATE PHOSPHORIBOSYLTRANSFERASE--MECHANISM

描述：核苷一磷酸合成提供了以下组分： DNA、RNA、ATP和NAD，需要磷酸核糖基转移酶的作用 （PRTases）以将核糖5-磷酸基团从其供体PRPP转移至 特定的杂环碱基。 PRTases是几个 危及生命的遗传性疾病，是合法的目标， 抗寄生虫剂、抗微生物剂和抗肿瘤剂。 该财团寻求 了解PRTase酶组的结构和功能。 乳清酸PRTase、次黄嘌呤-鸟嘌呤PRTase和喹啉酸PRTase已被广泛应用于临床。 结晶并测定其三维结构。 项目 试图揭示酶催化的结构和化学细节 通过OPRTase和QAPRTase的研究。 使用化学淬火技术， OPRTase动力学机制将被详细描述以允许理解 新发现的负协同作用的结合和催化。 的 OPRTase活性位点与亚单位界面接壤，需要移动的 蛋白质结构元件（环）由相邻的亚基贡献。 在亚基界面的结构相互作用可能是负责 协同性 对活性中心化学的贡献 将使用点突变体和部分环缺失体来确定元件 并通过确定与新合成的酶复合的酶的结构， 双底物类似物抑制剂。 一对催化剂的催化功能 将测定1类PRTases共有的羧酸残基。 QAPRTase代表了一种新发现的进化起源和新的 PRTase酶组的结构（2类PRTase折叠）。 的 X-射线将QAPRTase的结构细化，并研究其催化活性 将确定结构上类似于OPRTase中那些的位点残基。

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.