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Translating organellar glutamine codons : A case by case scenario?

Mathieu Frechin, Anne-Marie Duchêne and Hubert Dominique Becker

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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.

Authors

Mathieu Frechin

Université Louis Pasteur de Strasbourg; CNRS; Institut de Biologie Moléculaire et Cellulaire; Strasbourg, France

Anne-Marie Duchêne Corresponding author: anne-marie.duchene@ibmp-ulp.u-strasbg.fr

Université Louis Pasteur de Strasbourg; Strasbourg, France

Hubert Dominique Becker Corresponding author: h.becker@ibmc.u-strasbg.fr

Université Louis Pasteur de Strasbourg; Strasbourg, France

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