Translating organellar glutamine codons: a case by case scenario?
Aminoacyl-tRNAs are generally formed by direct attachment of an amino acid to tRNAs by aminoacyl-tRNA synthetases, but glutaminyl-tRNA (Q-tRNA) is an exception to this rule. Glutaminyl-tRNA(Gln) (Q-tRNA(Q)) is formed by this direct pathway in the eukaryotic cytosol and in a small subset of bacteria, but is formed by an indirect transamidation pathway in most bacteria and archaea. To date it is almost impossible to predict what pathway generates organellar Q-tRNA(Q) in a given eukaryote. All eukaryotic genomes sequenced so far, display a single glutaminyl-tRNA synthetase (QRS) gene which is at least responsible for the cytosolic QRS activity, as well as a gene coding for a mitochondrial ortholog of the essential GatB subunit of the tRNA-dependent amidotransferase (AdT). Indeed, QRS activity was found in protozoan mitochondria while AdT activity was characterized in plant organelles. The pathway for Q-tRNA(Q) synthesis in yeast and mammals mitochondria is still questionable.
Frechin
Mathieu
M
UPR Architecture et Réactivité de l'ARN, Université Louis Pasteur de Strasbourg, Strasbourg, France.
Duchêne
Anne-Marie
AM
Becker
Hubert Dominique
HD
D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism; D000818:Animals; D002736:Chloroplasts / Q000378:metabolism; D003062:Codon; D003600:Cytosol / Q000378:metabolism; D005975:Glutamate-tRNA Ligase / Q000378:metabolism; D005973:Glutamine / Q000737:chemistry*; D008928:Mitochondria / Q000378:metabolism; D008954:Models, Biological; D019884:Nitrogenous Group Transferases / Q000378:metabolism; D010944:Plants / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism
D003062:Codon; D012333:RNA, Messenger; D005973:Glutamine; D012343:RNA, Transfer; D019884:Nitrogenous Group Transferases; C047694:glutamyl-tRNA(Gln) amidotransferase; D000604:Amino Acyl-tRNA Synthetases; D005975:Glutamate-tRNA Ligase; C020659:glutaminyl-tRNA synthetase