Thiol redox control in the single mitochondrion of trypanosomes

锥虫属几种热带病的病原体，具有不寻常的以锥虫硫酮为基础的硫醇氧化还原代谢。这种寄生虫特有的代谢物由亚精胺和谷胱甘肽两分子合成，并由黄酶锥虫硫酮还原酶保持还原。所有参与生物合成的酶以及锥虫硫酮还原酶都只发生在细胞质中。在这里，锥虫硫酮通过直接的硫醇/二硫交换还原谷胱甘肽二硫，并提供各种氧化还原蛋白的还原等价物，如锥虫还蛋白、硫氧还蛋白和戊氧还蛋白。没有一种锥虫有机体在任何亚细胞细胞器中发现低分子质量硫醇(s)。本项目旨在阐明布鲁氏锥虫的谷胱甘肽和/或锥虫硫肽是否发生在阶段依赖性调节的单个线粒体中，硫醇如何转移到细胞器中，以及当寄生虫受到氧化应激时，细胞质和线粒体硫醇池的氧化还原平衡如何受到影响。第二种方法处理可能必不可少的线粒体硫氧还毒素型蛋白质的生理作用，该蛋白质在锥虫虫之外没有任何对应物。这些研究将包括重组蛋白的结构和功能分析，以及条件敲除寄生虫的产生和表征。计划中的工作将为我们提供对这些寄生虫单一线粒体的硫醇代谢的全面了解，并揭示新的硫氧还蛋白是否是低分子质量硫醇和线粒体硫醇过氧化物酶之间缺失的环节。

Trypanosomatids, to which belong the causative agents of several tropical diseases, have an unusual trypanothione-based thiol redox metabolism. The parasite-specific metabolite is synthesized from spermidine and two molecules of glutathione and kept reduced by the flavoenzyme trypanothione reductase. All enzymes involved in the biosynthesis as well as trypanothione reductase exclusively occur in the cytosol. Here, trypanothione reduces glutathione disulfide by direct thiol/disulfide exchange and provides the reducing equivalents for various redox proteins such as tryparedoxin, thioredoxin and glutaredoxin. For none of the trypanosomatid organism, the low molecular mass thiol(s) in any subcellular organelle has/have been identified. Aim of this project is to elucidate if glutathione and/or trypanothione occur in the stage-dependent regulated single mitochondrion of Trypanosoma brucei, how the thiols are transferred into the organelle and how the redox balance of the cytosolic and mitochondrial thiol pools are affected when the parasites are oxidatively stressed. The second approach deals with the physiological role of a probably essential mitochondrial thioredoxin-type protein which does not have any counterpart outside the trypanosomatids. These studies will comprise the structural and functional analysis of the recombinant protein as well as the generation and characterization of conditional knockout parasites. The planned work should provide us with a comprehensive insight into the thiol metabolism of the singular mitochondrion of these parasites and unravel if the novel thioredoxin is the missing link between the low molecular mass thiols and the mitochondrial thiol peroxidases.