Analysis of the Sam50 translocase of Excavate organisms supports evolution of divergent organelles from a common endosymbiotic event

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Kay, Christopher J. ; Lawler, Karen ; Kerr, Ian D. (2013)
  • Publisher: Portland Press Ltd.
  • Journal: Bioscience Reports, volume 33, issue 6 (issn: 0144-8463, eissn: 1573-4935)
  • Related identifiers: doi: 10.1042/BSR20130049, pmc: PMC3848468
  • Subject: HA, haemaglutinin | membrane | TBS-T, TBS with 0.1% (v/v) Tween | DSP, dithiobis(succinimidyl propionate) | TOM, translocase of the outer membrane | SAM, sorting and assembly machinery | hydrogenosome | Trichomonas | S2 | OEP, outer envelope protein | POTRA, polypeptide-transport-associated domain | MBS, maleimidobenzoyl-hydroxysuccinimide ester | evolution | DTT, dithiothreitol | Original Paper | CDD, conserved domains database | β-barrel | HMM, hidden Markov model | EST, Expressed Sequence Tag | TOC, translocon of the outer membrane of the chloroplast | aa, amino acids | BN-PAGE, Blue native-polyacrylamide gel electrophoresis | organelles | OMP, outer membrane protein
    mesheuropmc: biochemical phenomena, metabolism, and nutrition | fungi

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.
  • References (1)

    1 Kutik, S., Stojanovski, D., Becker, L., Becker, T., Meinecke, M., Kru¨ger, V., Prinz, C., Meisinger, C., Guiard, B., Wagner, R. et al. (2008) Dissecting membrane insertion of mitochondrial beta-barrel proteins. Cell 132, 1011-1024

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