CRYSTAL STRUCTURE OF TOXOPLASMA GONDII HGPRT

描述：（改编自申请人摘要）。 弓形虫a 普遍寄生原生动物，导致显著的发病率和死亡率 获得性免疫缺陷综合症（艾滋病）患者，以及 在器官移植患者中。 目前T.弓形虫 感染往往产生严重的副作用，导致停止 疗法 因此，广泛认识到具有新颖性的新药是可能的。 迫切需要行动机制， 弓形虫病 自从T.弓形虫不能从头合成 嘌呤核苷酸，而是补救宿主嘌呤，申请人的长 长期研究目标是利用寄生虫代谢的这一关键方面 他们想设计嘌呤补救抑制剂， 可挽救的有毒嘌呤底物（颠覆性底物）， 或者杀死弓形虫。 两种酶控制嘌呤补救， 弓形虫：次黄嘌呤-鸟嘌呤磷酸核糖基转移酶（HGPRT）和 腺苷激酶 在这项拨款申请中，申请人的目标是 T.弓形虫HGPRT。 他们成功地过表达并结晶了T. 弓形虫HGPRT，因此现在可以确定其晶体 结构，目的是进行基于结构的药物设计。 在这项拨款申请中，他们提出解决的晶体结构 弓形虫HGPRT，并利用此结构设计有效的， 这种酶的选择性抑制剂和破坏性底物。 的 他们方法的核心是确定 T. X线弓形虫HGPRT 结晶学 他们结晶了T.弓形虫HGPRT在两种不同的 能将X射线分解到2.75（分辨率）的晶体形式。 支持 这一中心目标，他们建议：完成两者的表征 T.弓形虫HGPRT同工酶;制备和表征几个点突变 中医弓形虫HGPRT活性位点残基，他们假设控制 酶选择性利用黄嘌呤，合成多种HGPRT 过渡态类似物可能是有效的抑制剂;并测试这些 和其他抑制酶的抑制剂， 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.