Abstract The evolution of mitochondrial protein import and the systems that mediate it marks the boundary between the endosymbiotic ancestor of mitochondria and a true organelle that is under the control of the nucleus. Protein import has been studied in great detail in Saccharomyces cerevisiae. More recently, it has also been extensively investigated in the parasitic protozoan Trypanosoma brucei, making it arguably the second best studied system. A comparative analysis of the protein import complexes of yeast and trypanosomes is provided. Together with data from other systems, this allows to reconstruct the ancestral features of import complexes that were present in the last eukaryotic common ancestor (LECA) and to identify which subunits were added later in evolution. How these data can be translated into plausible scenarios is discussed, providing insights into the evolution of (i) outer membrane protein import receptors, (ii) proteins involved in biogenesis of α-helically anchored outer membrane proteins, and (iii) of the intermembrane space import and assembly system. Finally, it is shown that the unusual presequence-associated import motor of trypanosomes suggests a scenario of how the two ancestral inner membrane protein translocases present in LECA evolved into the single bifunctional one found in extant trypanosomes.

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线粒体蛋白质输入的进化——来自锥虫的教训

摘要 线粒体蛋白质输入及其介导系统的进化标志着线粒体的内共生祖先与受细胞核控制的真正细胞​​器之间的边界。在酿酒酵母中对蛋白质输入进行了非常详细的研究。最近，它还在寄生原生动物布氏锥虫中进行了广泛的研究，使其成为研究第二好的系统。提供了酵母和锥虫的蛋白质输入复合物的比较分析。与来自其他系统的数据一起，这允许重建存在于最后一个真核共同祖先 (LECA) 中的输入复合物的祖先特征，并确定哪些亚基是在进化后期添加的。讨论了如何将这些数据转化为合理的场景，提供对 (i) 外膜蛋白导入受体、(ii) 参与 α 螺旋锚定外膜蛋白生物发生的蛋白质以及 (iii) 膜间空间导入和组装系统的进化的见解。最后，表明锥虫不寻常的前序列相关输入马达表明存在于 LECA 中的两个祖先内膜蛋白转位酶如何进化成在现存锥虫中发现的单一双功能转位酶的情景。