title: A mechanism for functional segregation of mitochondrial and cytosolic genetic codes.
abstract: The coexistence of multiple gene translation machineries is a feature of eukaryotic cells and a result of the endosymbiotic events that gave rise to mitochondria, plastids, and other organelles. The conditions required for the integration of these apparatuses within a single cell are not understood, but current evidence indicates that complete ablation of the mitochondrial protein synthesis apparatus and its substitution by its cytosolic equivalent is not possible. Why certain mitochondrial components and not others can be substituted by cytosolic equivalents is not known. In trypanosomatids this situation reaches a limit, because certain aminoacyl-tRNA synthetases are mitochondrial specific despite the fact that all tRNAs in these organisms are shared between cytosol and mitochondria. Here we report that a mitochondria-specific lysyl-tRNA synthetase in Trypanosoma has evolved a mechanism to block the activity of the enzyme during its synthesis and translocation. Only when the enzyme reaches the mitochondria is it activated through the cleavage of a C-terminal structural extension, preventing the possibility of the enzyme being active in the cytosol.
authors.affiliation: Institute for Research in Biomedicine, Barcelona, Catalonia, Spain.
authors.forename: Yaiza
authors.initials: Y
authors.lastname: Español
authors.forename: Daniel
authors.initials: D
authors.lastname: Thut
authors.forename: André
authors.initials: A
authors.lastname: Schneider
authors.forename: Lluís
authors.initials: L
authors.lastname: Ribas de Pouplana
mesh_terms: D000595:Amino Acid Sequence; D003600:Cytosol / Q000201:enzymology*; D008250:Lysine-tRNA Ligase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis; D021381:Protein Transport; D020539:Sequence Analysis, Protein; D046249:Transfer RNA Aminoacylation; D014346:Trypanosoma brucei brucei / Q000201:enzymology* / Q000235:genetics
chemical_list: D008250:Lysine-tRNA Ligase