THE APICOPLAST--A TARGET FOR PARASITICIDAL CHEMOTHERAPY

顶复合体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（与艾滋病相关的重要机会性寄生虫）。广泛的耐药性和现有治疗方法的低耐受性使得开发针对这些寄生虫的新型化疗策略变得更加紧迫。因此，发现这些生物体含有对其生存至关重要的质体引起了相当大的兴趣。几种通常只对原核生物有效的抗生素（包括大环内酯类药物和氟喹诺酮类药物）显示出对刚地弓形虫和其他顶质体的活性，并且有几种观点表明，这些化合物针对的是顶质体功能。本提案的目的是通过：(1)检查利福霉素抗生素（被认为抑制质体编码的RNA聚合酶）中观察到的死亡动力学，并培养对利福霉素耐药的弓形虫突变体。(2)结合生物信息学、生物化学和遗传学方法，鉴定和表征核编码质体拓扑异构酶（氟喹诺酮类抗生素的可能靶标）。

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.