Roles of lipoate pathways in Plasmodium survival

描述（由申请人提供）：疟原虫寄生虫每年造成超过5亿例疟疾病例。在红细胞发育的无性阶段，疟原虫从人类血清中获得某些营养素，同时保留合成其他营养素的能力。我们正在研究一种称为硫辛酸的必需酶辅因子及其在恶性疟原虫中的代谢。我们最近的研究表明，红细胞期寄生虫是营养缺陷型的硫辛酸，即使他们包含一个代谢途径来合成这种辅因子。顶质体细胞器中的蛋白质依赖于硫辛酸合成，而寄生虫体内的蛋白质依赖于清除，不能获得顶质体中合成的硫辛酸。建议的研究集中在两个方面的硫辛酸清除，并采用生物化学，细胞生物学和遗传方法的组合。我们的第一个目标是确定如何从外部环境中摄取硫辛酸，并附着在寄生虫寄生虫体内的特定蛋白质上。这些实验将确定在摄取硫辛酸的限速步骤，他们将锻造一个详细的链接之间的硫辛酸附着酶和它们的蛋白质底物。我们的第二个目标是确定的脂肪酸依赖的线粒体蛋白是必不可少的寄生虫生存和确定这些蛋白质在寄生虫生物学的作用。在其他生物体中，这些蛋白质形成大的多酶复合物，其可以具有多种代谢和非代谢作用。我们的实验将解剖这些蛋白质的结构域结构，确定它们的活性，并确定它们在蛋白质复合物中的结合伙伴。遗传学方法将定义的作用，在血液阶段的寄生虫的生存的脂肪酸代谢蛋白。由于依赖于宿主营养素，这些蛋白质代表了寄生虫生物学的脆弱方面，可以在几个层面上进行靶向。

DESCRIPTION (provided by applicant): Plasmodium parasites are responsible for over half a billion malaria cases annually. During the asexual stages of development in red blood cells, malaria parasites acquire certain nutrients from human serum while retaining the ability to synthesize others. We are studying an essential enzyme cofactor called lipoate and its metabolism in Plasmodium falciparum. Our recent studies demonstrate that erythrocytic stage parasites are auxotrophic for lipoate, even though they contain a metabolic pathway to synthesize this cofactor. Proteins in the apicoplast organelle rely on lipoate synthesis while proteins in the parasite mitochondrion rely on scavenging and cannot obtain lipoate synthesized in the apicoplast. The proposed studies are focused on two aspects of lipoate scavenging and employ a combination of biochemical, cell biology and genetic approaches. Our first aim is to define how lipoate is taken up from the external environment and attached to specific proteins in the parasite mitochondrion. These experiments will identify rate limiting steps in the uptake of lipoate and they will forge a detailed link between the lipoate attachment enzymes and their protein substrates. Our second aim is to identify the lipoate-dependent mitochondrial proteins that are essential for parasite survival and determine the roles of these proteins in parasite biology. In other organisms, these proteins form large multi-enzyme complexes which can have a variety of metabolic and non-metabolic roles. Our experiments will dissect the domain structure of these proteins, determine their activities, and identify their binding partners in protein complexes. Genetic approaches will define the roles of lipoate metabolism proteins in the survival of blood stage parasites. By virtue of relying on a host nutrient, these proteins represent a vulnerable aspect of parasite biology which could be targeted at several levels.