Dual-targeted tRNA-dependent amidotransferase ensures both mitochondrial and chloroplastic Gln-tRNAGln synthesis in plants.

Claire Pujol (1) , Marc Bailly (2) , Daniel Kern (2) , Laurence Maréchal-Drouard (1) , Hubert Becker (2) , Anne-Marie Duchêne (1)

1 IBMP - Institut de Biologie Moléculaire des Plantes
2 ARN - Architecture et réactivité de l'ARN

Aminoacyl-tRNAs are generally formed by direct attachment of an amino acid to tRNAs by aminoacyl-tRNA synthetases, but Gln-tRNA is an exception to this rule. Gln-tRNA(Gln) is formed by this direct pathway in the eukaryotic cytosol and in protists or fungi mitochondria but is formed by an indirect transamidation pathway in most of bacteria, archaea, and chloroplasts. We show here that the formation of Gln-tRNA(Gln) is also achieved by the indirect pathway in plant mitochondria. The mitochondrial-encoded tRNA(Gln), which is the only tRNA(Gln) present in mitochondria, is first charged with glutamate by a nondiscriminating GluRS, then is converted into Gln-tRNA(Gln) by a tRNA-dependent amidotransferase (AdT). The three subunits GatA, GatB, and GatC are imported into mitochondria and assemble into a functional GatCAB AdT. Moreover, the mitochondrial pathway of Gln-tRNA(Gln) formation is shared with chloroplasts as both the GluRS, and the three AdT subunits are dual-imported into mitochondria and chloroplasts.

Domaines: Biochimie, Biologie Moléculaire; Biologie cellulaire

Claire Pujol, Marc Bailly, Daniel Kern, Laurence Maréchal-Drouard, Hubert Becker, et al.. Dual-targeted tRNA-dependent amidotransferase ensures both mitochondrial and chloroplastic Gln-tRNAGln synthesis in plants.. Proceedings of the National Academy of Sciences of the United States of America, 2008, 105 (17), pp.6481-5. ⟨10.1073/pnas.0712299105⟩. ⟨hal-00356301⟩