Oxidative protein folding in the mitochondrial intermembrane space of parasitic protists

氧化蛋白折叠是酵母和人类线粒体膜间隙蛋白质的主要输入机制。这一过程需要通过适配酶Mia40识别和氧化胞质输入底物的半胱氨酸残基。二硫键的形成导致蛋白质底物在膜间空间的折叠和捕获。被还原的Mia40随后将底物的还原等量转移到Erv1/ALR， Erv1/ALR作为一个继电器，将电子提供给细胞色素c和呼吸链。线粒体膜间隙的氧化蛋白折叠和编码Mia40和Erv1/ALR的基因是必不可少的。因此，令人惊讶的是，在许多原生生物，包括一些医学和经济上最重要的寄生虫的基因组中，没有发现mia40同源物。此外，寄生原生生物的erv同源物的结构和机制（以及明显的进口）与酵母和人类的Erv1/ALR有很大的不同。因此，寄生原生生物的氧化蛋白折叠与人类的氧化蛋白折叠有着根本的不同。然而，到目前为止，究竟是哪种蛋白质在功能上取代了Mia40，以及氧化蛋白折叠究竟是如何在寄生原生生物中发生的，都是完全未知的。本项目的目的是比较鉴定模型利什曼原虫和最重要的人类疟疾寄生虫恶性疟原虫中假设的mia40替代。一方面，这应该为重要病原体的氧化蛋白折叠提供基本的见解。另一方面，所识别的差异和相似性不仅揭示了真核生物中这一重要过程的多样性，而且揭示了其机制原理的保守性。

Oxidative protein folding is the predominant import mechanism for proteins of the mitochondrial intermembrane space in yeast and human. This process requires the recognition and oxidation of cysteine residues of cytosolic import substrates by the adapter enzyme Mia40. The formation of disulfide bonds results in folding and trapping of the protein substrates in the intermembrane space. Reduced Mia40 subsequently transfers the substrates' reducing equivalents to Erv1/ALR, which functions as a relay and feeds the electrons to cytochrome c and the respiratory chain. Oxidative protein folding in the mitochondrial intermembrane space and the genes encoding Mia40 & Erv1/ALR are essential. Hence, it is rather surprising that no Mia40-homologue can be identified in the genomes of many protists, including several of the medically and economically most important parasites. Moreover, the architecture and mechanism (and apparently the import) of Erv-homologues from parasitic protists deviate significantly from yeast and human Erv1/ALR. Oxidative protein folding in parasitic protists is therefore fundamentally different from oxidative protein folding in human. However, so far it is completely unknown which protein functionally replaces Mia40 and how oxidative protein folding exactly occurs in parasitic protists. The objective of this project is the comparative identification of the postulated Mia40-replacement in the model parasite Leishmania tarentolae and the most important human malaria parasite Plasmodium falciparum. On the one hand, this should provide fundamental insights into oxidative protein folding of important of pathogens. On the other hand, the identified differences and similarities should reveal not only the diversity but also the conservation of mechanistic principles of this essential process in eukaryotes.