Euglena gracilis and Trypanosomatids Possess Common Patterns in Predicted Mitochondrial Targeting Presequences
Euglena gracilis possessing chloroplasts of secondary green algal origin and parasitic trypanosomatids Trypanosoma brucei, Trypanosoma cruzi and Leishmania major belong to the protist phylum Euglenozoa. Euglenozoa might be among the earliest eukaryotic branches bearing ancestral traits reminiscent of the last eukaryotic common ancestor (LECA) or missing features present in other eukaryotes. LECA most likely possessed mitochondria of endosymbiotic α-proteobacterial origin. In this study, we searched for the presence of homologs of mitochondria-targeted proteins from other organisms in the currently available EST dataset of E. gracilis. The common motifs in predicted N-terminal presequences and corresponding homologs from T. brucei, T. cruzi and L. major (if found) were analyzed. Other trypanosomatid mitochondrial protein precursor (e.g., those involved in RNA editing) were also included in the analysis. Mitochondrial presequences of E. gracilis and these trypanosomatids seem to be highly variable in sequence length (5–118 aa), but apparently share statistically significant similarities. In most cases, the common (M/L)RR motif is present at the N-terminus and it is probably responsible for recognition via import apparatus of mitochondrial outer membrane. Interestingly, this motif is present inside the predicted presequence region in some cases. In most presequences, this motif is followed by a hydrophobic region rich in alanine, leucine, and valine. In conclusion, either RR motif or arginine-rich region within hydrophobic aa-s present at the N-terminus of a preprotein can be sufficient signals for mitochondrial import irrespective of presequence length in Euglenozoa.
KeywordsCleaved targeting sequence Euglenids Euglenozoa Excavata Kinetoplastids Mitochondrial protein import Protein motifs
This work was supported by Scientific Grant Agency of the Slovak Ministry of Education and the Academy of Sciences (grants 1/0416/09 and 1/0393/09), Comenius University Grants (UK/54/2011), Czech Science Foundation grant P506/11/1320, and is the result of the project implementation: “The Improvement of Centre of excellence for exploitation of informational biomacromolecules in improvement of quality of life,” ITMS 26240120027, supported by the Research & Development Operational Programme funded by the ERDF. This paper has been published in frame of the project “Strengthening research institutions at the University of Ostrava,” CZ.1.07/2.3.00/30.0047, which is co-financed by the European Social Fund and the state budget of the Czech Republic. We thank Dr. Broňa Brejová (Department of Computer Science, Faculty of Mathematics, Physics, and Informatics, Comenius University, Bratislava, Slovakia), Dr. Tomáš Vinař (Department of Applied Informatics, Faculty of Mathematics, Physics, and Informatics, Comenius University, Bratislava, Slovakia), and Dr. Pavel Doležal and Vojtěch Žárský (both from the Department of Parasitology, Faculty of Science, Charles University in Prague) for help with the choice of appropriate bioinformatic programs to analyze the data.
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