WT AND MUTANTS OF TS-DHFR FROM C HOMINIS

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 人隐孢子虫被列为生物防御优先事项，因为隐孢子虫病是一种新出现的传染病，没有有效的治疗方法。二氢叶酸还原酶(DHFR)的抗叶酸抑制剂已被证明是治疗其他寄生虫的有效药物，但对人毛滴虫无效，部分原因是与该酶的结合亲和力较低。对人弓形虫二氢叶酸还原酶-胸苷合成酶(DHFR-TS)两种晶体结构中蛋白质：配体相互作用的分析表明，人二氢叶酸还原酶DHFR活性部位的特定残基与抑制剂的相互作用为观察到的抗叶酸抗性提供了可能的结构基础。与人DHFR结构的比较揭示了活性部位的差异，这可能被用来设计物种选择性抑制剂。我们正在使用一种新的概念，结构导向库设计，它融合了组合化学和基于结构的药物设计的想法，以创造一流的人芽孢杆菌DHFR抑制剂，对病原体既有效又有选择性。 在这次同步加速器运行期间，我们计划收集与几种抑制剂结合的DHFR-TS共晶体的数据。此外，我们将收集DHFR-TS晶体的数据，这些数据在残基上有几个突变，被认为在催化和底物/抑制剂结合中发挥关键作用。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Cryptosporidium hominis is listed as a biodefense priority since cryptosporidiosis is an emerging infectious disease with no effective therapies. Antifolate inhibitors of dihydrofolate reductase (DHFR) have proven to be effective therapeutics against other parasitic protozoa, but are ineffective against C. hominis due, in part, to low binding affinities to the enzyme. An analysis of the protein:ligand interactions in two crystal structures of dihydrofolate reductase-thymidylate synthase (DHFR-TS) from C. hominis reveals that the interactions of specific residues in the active site of C. hominis DHFR with inhibitors provide a possible structural basis for the observed antifolate resistance. A comparison with the structure of human DHFR reveals active site differences that may be exploited for the design of species-selective inhibitors. We are working with a new concept, structure-guided library design that merges ideas from combinatorial chemistry and structure-based drug design, to create best-in-class C. hominis DHFR inhibitors that are both potent and selective for the pathogenic organism. During this synchrotron run, we plan to collect data for the co-crystals of DHFR-TS bound to several inhibitors. Additionally, we will be collecting data on crystals of DHFR-TS with several mutations at residues proposed to play a key role in catalysis and substrate/inhibitor binding.