Mitochondrial translation in absence of local tRNA aminoacylation and methionyl tRNAMet formylation in Apicomplexa

Authors

  • Paco Pino,

    1. Department of Microbiology and Molecular Medicine, CMU, University of Geneva, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland.
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  • Eric Aeby,

    1. Department of Chemistry and Biochemistry, University of Berne, Freiestrasse 3, CH-3012 Bern, Switzerland.
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    • These authors equally contributed to the work and are listed in alphabetic order.

  • Bernardo Javier Foth,

    1. Department of Microbiology and Molecular Medicine, CMU, University of Geneva, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland.
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    • These authors equally contributed to the work and are listed in alphabetic order.

  • Lilach Sheiner,

    1. Department of Microbiology and Molecular Medicine, CMU, University of Geneva, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland.
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    • These authors equally contributed to the work and are listed in alphabetic order.

  • Thierry Soldati,

    1. Department of Biochemistry, University of Geneva, Science II, Quai Ernest Ansermet, 1211 Geneva 4, Switzerland.
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  • Andre Schneider,

    1. Department of Chemistry and Biochemistry, University of Berne, Freiestrasse 3, CH-3012 Bern, Switzerland.
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  • Dominique Soldati-Favre

    Corresponding author
    1. Department of Microbiology and Molecular Medicine, CMU, University of Geneva, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland.
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E-mail dominique.soldati-favre@unige.ch; Tel. (+41) 22 379 5672; Fax (+41) 22 379 5702.

Summary

Apicomplexans possess three translationally active compartments: the cytosol, a single tubular mitochondrion, and a vestigial plastid organelle called apicoplast. Mitochondrion and apicoplast are of bacterial evolutionary origin and therefore depend on a bacterial-like translation machinery. The minimal mitochondrial genome contains only three ORFs, and in Toxoplasma gondii the absence of mitochondrial tRNA genes is compensated for by the import of cytosolic eukaryotic tRNAs. Although all compartments require a complete set of charged tRNAs, the apicomplexan nuclear genomes do not hold sufficient aminoacyl-tRNA synthetase (aaRSs) genes to be targeted individually to each compartment. This study reveals that aaRSs are either cytosolic, apicoplastic or shared between the two compartments by dual targeting but are absent from the mitochondrion. Consequently, tRNAs are very likely imported in their aminoacylated form. Furthermore, the unexpected absence of tRNAMet formyltransferase and peptide deformylase implies that the requirement for a specialized formylmethionyl-tRNAMet for translation initiation is bypassed in the mitochondrion of Apicomplexa.

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