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

Mol Microbiol. 2010 Mar 31. [Epub ahead of print]

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

Pino P, Aeby E, Foth BJ, Sheiner L, Soldati T, Schneider A, Soldati-Favre D.

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

Abstract
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 tRNA(Met) formyltransferase and peptide deformylase implies that the requirement for a specialized formylmethionyl-tRNA(Met) for translation initiation is bypassed in the mitochondrion of Apicomplexa.

PMID: 20374492 [PubMed - as supplied by publisher]