*School of Life Sciences, University of Nottingham Medical School, Queen's Medical Centre, Nottingham NG7 2UH, U.K.
Biosci Rep. 2013 Dec 3;33(6):e00084. doi: 10.1042/BSR20130049.
As free-living organisms the ancestors of mitochondria and plastids encoded complete genomes, proteomes and metabolomes. As these symbionts became organelles all these aspects were reduced - genomes have degenerated with the host nucleus now encoding the most of the remaining endosymbiont proteome, while the metabolic processes of the symbiont have been streamlined to the functions of the emerging organelle. By contrast, the topology of the endosymbiont membrane has been preserved, necessitating the development of complex pathways for membrane insertion and translocation. In this study, we examine the characteristics of the endosymbiont-derived β-barrel insertase Sam501 in the excavate super-group. A candidate is further characterized in Trichomonas vaginalis, an unusual eukaryote possessing degenerate hydrogen-producing mitochondria called hydrogenosomes. This information supports a mitochondriate eukaryotic common ancestor with a similarly evolved β-barrel insertase, which has continued to be conserved in degenerate mitochondria.
作为自由生活的生物体，线粒体和质体的祖先编码了完整的基因组、蛋白质组和代谢组。随着这些共生体成为细胞器，所有这些方面都减少了——基因组退化了，宿主细胞核现在编码了大部分剩余的内共生体蛋白质组，而共生体的代谢过程已经简化为新出现的细胞器的功能。相比之下，内共生体膜的拓扑结构得以保留，这需要为膜插入和易位开发复杂的途径。在这项研究中，我们研究了挖掘超组中内共生体衍生的β桶插入酶 Sam501 的特征。在一种被称为氢化酶体的具有退化产氢线粒体的异常真核生物阴道毛滴虫中，进一步鉴定了一个候选物。这些信息支持了一个具有类似进化的β桶插入酶的线粒体真核生物共同祖先，该插入酶在退化的线粒体中继续被保守。
