THE APICOPLAST--A TARGET FOR PARASITICIDAL CHEMOTHERAPY

尖端复合门包括许多人类病原体，如疟原虫(疟疾的病原体)、弓形虫和隐孢子虫(与艾滋病有关的重要机会性寄生虫)。广泛的耐药性和现有治疗方法的不良耐受性为开发针对这些寄生虫的新的化疗策略提供了新的紧迫性。因此，这些生物体中含有对它们的生存至关重要的一种质体的发现，引起了人们极大的兴趣。几种通常只对原核生物有效的抗生素(包括大环内酯类和氟喹诺酮类)显示出对弓形虫和其他复合顶体的活性，几种论点表明这些化合物以质外体功能为目标。这项建议的目的是通过以下方式验证这一假设：(1)检查在利福霉素抗生素中观察到的死亡动力学(被认为抑制叶绿体编码的RNA聚合酶)，并开发对利福霉素具有抗药性的弓形虫突变体。(2)结合生物信息学、生物化学和遗传学方法，鉴定和鉴定核编码的质体拓扑异构酶(氟喹诺酮类抗生素的可能靶点)。

The phylum Apicomplexa includes many human pathogens, such as Plasmodium (the causative agent of malaria), Toxoplasma and Cryptosporidium (important opportunistic parasites associated with AIDS). Widespread drug-resistance and the poor tolerance of treatments available have lent new urgency to the development of novel chemotherapeutic strategies for these parasites. The discovery that these organisms harbor a plastid which is essential for their survival has therefore produced considerable interest. Several antibiotics that are normally effective only against prokaryotic organisms (including macrolides and fluoroquinolones) exhibit activity against Toxoplasma gondii and other apicomplexans, and several lines of argument suggest that these compounds target apicoplast functions. The objectives of this proposal are to test this hypothesis, by: (1) Examining the kinetics of death observed in rifamycin antibiotics (thought to inhibit the plastid-encoded RNA polymerase), and developing T. gondii mutants resistant to rifamycins. (2) Identifying and characterizing nuclear-encoded plastid topoisomerases (the probable target of fluoroquinolone antibiotics), using a combination of bioinformatic, biochemical, and genetic approaches.