CRYSTAL STRUCTURE OF TOXOPLASMA GONDII HGPRT

描述：(改编自申请人摘要)。弓形虫，一种 普遍存在的寄生原生动物，导致严重的发病率和死亡率 在获得性免疫缺陷综合征(AIDS)患者中， 在器官移植患者中。弓形虫的现行治疗方案 感染通常会产生严重的副作用，导致停止 心理治疗。因此，人们普遍认为，新药具有新颖性 迫切需要行动机制来治疗 弓形虫病。由于弓形虫不能从头合成 嘌呤核苷酸，而不是挽救宿主嘌呤，申请人的长 学期研究目标是利用寄生新陈代谢的这一关键方面 优势：他们想要设计嘌呤回收抑制剂和 可回收的有毒嘌呤底物(颠覆性底物) 灭活或杀死弓形虫。两种酶控制嘌呤的回收 弓形虫：次黄嘌呤-鸟嘌呤磷酸核糖基转移酶(HGPRT)和 腺苷激酶。在这份拨款申请中，申请者的目标是 弓形虫HGPRT.它们成功地过表达和结晶了T. Gondii HGPRT，因此现在可以确定它的晶体 结构，以进行基于结构的药物设计。 在这项拨款申请中，他们建议解决 弓形虫HGPRT，并利用这种结构设计有效的和 这种酶的选择性抑制物和颠覆性底物。这个 他们方法的核心是确定 用X射线研究弓形虫HGPRT的三维结构 结晶学。他们已经将弓形虫HGPRT结晶成两种不同的 使X射线衍射到2.75(分辨率)的晶体。为了支持…… 这一中心目标，他们建议：完成对两者的描述 弓形虫HGPRT同工酶；几种点突变的制备和鉴定 他们推测控制弓形虫HGPRT活性部位残基的 酶法选择性利用黄嘌呤；合成几种HGPRT 过渡态类似物可能是强有力的抑制剂；并测试这些 和其他抑制酶的药物，以及体内的寄生虫 体外细胞培养。

DESCRIPTION: (Adapted from Applicant's Abstract). Toxoplasma gondii, a pervasive parasitic protozoan, causes significant morbidity and mortality among patients with Acquired Immune Deficiency Syndrome (AIDS), as well as among organ transplant patients. Current treatment regimens for T. gondii infections often produce severe side effects, leading to the cessation of therapy. Thus, it is widely recognized that new drugs having novel mechanisms of action are urgently needed for the treatment of toxoplasmosis. Since T. gondii are incapable of de novo synthesis of purine nucleotides, but instead salvage host purines, the applicant's long term research goal is to use this crucial aspect of parasitic metabolism to advantage: They want to design purine salvage inhibitors and salvageable toxic purine substrates (subversive substrates) that will inactivate or kill toxoplasma. Two enzymes control purine salvage in toxoplasma: hypoxanthine-guanine phosphoribosyltransferase (HGPRT) and adenosine kinase. In this grant application, the applicants are targeting T. gondii HGPRT. they have successfully overexpressed and crystallized T. gondii HGPRT, and thus are now in a position to determine its crystal structure, for the purpose of carrying out structure-based drug design. In this grant application, they propose to solve the crystal structure of Toxoplasma gondii HGPRT, and to use this structure to design potent and selective inhibitors and subversive substrates of this enzyme. The centerpiece of their approach is the determination of the three-dimensional structure of T. gondii HGPRT using X-ray crystallography. They have crystallized T. gondii HGPRT in two different crystal forms that diffract X-rays to 2.75 ( resolution. In support of this central aim, they propose to: complete the characterization of both T. gondii HGPRT isozymes; prepare and characterize several point mutations of T. gondii HGPRT active site residues that they hypothesize control the selective utilization of xanthine by the enzyme; synthesize several HGPRT transition state analogues likely to be potent inhibitors; and test these and other inhibitors against the enzyme, and against the parasite in in vitro cell culture.