Ribosome structure determination from Apicomplexan parasites

项目总结/摘要 顶复门含有许多寄生虫，它们感染人类和动物并引起疾病， 包括导致疟疾、弓形虫病和巴贝虫病的病原体。巴贝虫是一种蜱传的细胞内 一种导致严重至致命疾病的寄生虫，由于气候变化，其地理分布范围扩大 以及在森林地区增加郊区开发。目前还没有针对人类巴贝斯虫病的疫苗， 目前的疗法具有有限的功效。考虑到巴贝虫物种复杂的生命周期， 依赖于对它们基因表达的精确控制，而基因表达主要是在转录后调节的（例如， 蛋白质合成）。Bababelles物种有一个独特的，非光合作用的细胞器称为顶质体， 源自次级内共生事件。除了在细胞质中有核糖体， 顶质体含有自己的核糖体。人们对这些核糖体的结构知之甚少， 尽管它们被认为是高度简化的，具有类似原核生物的成分。它们被抑制， 抗寄生虫活性有限的抗菌药物。缺乏任何分子结构 顶质体核糖体限制了具有改进的抗寄生虫特性的抗生素的合理设计。上 为了实现本研究的目的，我们将建立表达血凝素（HA）的分歧巴氏杆菌菌株， 在顶质体的外膜上标记的磷酸丙糖转运蛋白。这种策略将使亲和力 纯化高质量的细胞器制剂，然后纯化顶质体核糖体。在 第二个目标，我们将确定顶质体核糖体的组成部分，并确定其结构， 电子显微镜（cryo-EM）。因此，我们的目标是阐明 顶复体寄生虫用于在高度特化的顶质体细胞器中合成蛋白质。我们的工作将 为研究这些寄生虫的基因调控机制奠定了基础， 设计更好的抗寄生虫药。

PROJECT SUMMARY/ABSTRACT The Apicomplexa phylum contains many parasites that infect and cause disease in humans and animals, including the agents that cause malaria, toxoplasmosis, and babesiosis. Babesia is a tick-borne intracellular parasite that causes severe to fatal diseases, with broadening geographic distribution because of climate change and increasing suburban developments in forested areas. There is no vaccine against human babesiosis, and the current therapies have limited efficacy. Considering the complex life cycle of Babesia species, their survival depends on the precise control of their gene expression, which is mostly regulated post-transcriptionally (e.g., during protein synthesis). Babesia species have a unique, non-photosynthetic organelle named apicoplast, derived from a secondary endosymbiotic event. In addition to having ribosomes in its cytoplasm and mitochondria, the apicoplast contains its own ribosomes. Little is known about the structure of these ribosomes, although they are thought to be highly simplified, with prokaryotic-like components. They are inhibited by antibacterial drugs that have some limited antiparasitic activity. The absence of a molecular structure of any apicoplast ribosomes limits the rational design of antibiotics with improved antiparasitic properties. In the first aim of this research proposal, we will establish a Babesia divergens strain expressing an hemagglutinin (HA)- tagged triose phosphate transporter on the outer membrane of the apicoplast. This strategy will allow the affinity purification of a high-quality organelle preparation, followed by the purification of apicoplast ribosomes. In the second aim, we will define the components of apicoplast ribosomes and determine their structure using cryo- electron microscopy (cryo-EM). Our goal is thus to elucidate the fundamental molecular machinery that apicomplexan parasites use to synthesize proteins in the highly specialized apicoplast organelle. Our work will lay the foundation for studies that interrogate these parasites' gene regulation mechanisms and help inspire the design of better antiparasitic agents.