title: Evolution of the Glx-tRNA synthetase family: the glutaminyl enzyme as a case of horizontal gene transfer.
abstract: An important step ensuring the fidelity in protein biosynthesis is the aminoacylation of tRNAs by aminoacyl-tRNA synthetases. The accuracy of this process rests on a family of 20 enzymes, one for each amino acid. One exception is the formation of Gln-tRNA(Gln) that can be accomplished by two different pathways: aminoacylation of tRNA(Gln) with Gln by glutaminyl-tRNA synthetase (GlnRS; EC 6.1.1.18) or transamidation of Glu from Glu-tRNA(Gln) mischarged by glutamyl-tRNA synthetase (GluRS; EC 6.1.1.17). The latter pathway is widespread among bacteria and organelles that, accordingly, lack GlnRS. However, some bacterial species, such as Escherichia coli, do possess a GlnRS activity, which is responsible for Gln-tRNA(Gln) formation. In the cytoplasm of eukaryotic cells, both GluRS and GlnRS activities can be detected. To gain more insight into the evolutionary relationship between GluRS and GlnRS enzyme species, we have now isolated and characterized a human cDNA encoding GlnRS. The deduced amino acid sequence shows a strong similarity with other known GlnRSs and with eukaryotic GluRSs. A molecular phylogenetic analysis was conducted on the 14 GlxRS (GluRS or GlnRS) sequences available to date. Our data suggest that bacterial GlnRS has a eukaryotic origin and was acquired by a mechanism of horizontal gene transfer.
authors.affiliation: Laboratoire de Biologie des Tumeurs Humaines, Unité de Recherche Associée 1156, Institut Gustave Roussy, Villejuif, France.
authors.forename: V
authors.initials: V
authors.lastname: Lamour
authors.forename: S
authors.initials: S
authors.lastname: Quevillon
authors.forename: S
authors.initials: S
authors.lastname: Diriong
authors.forename: V C
authors.initials: VC
authors.lastname: N'Guyen
authors.forename: M
authors.initials: M
authors.lastname: Lipinski
authors.forename: M
authors.initials: M
authors.lastname: Mirande
mesh_terms: D000595:Amino Acid Sequence; D000604:Amino Acyl-tRNA Synthetases / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics; D002893:Chromosomes, Human, Pair 3; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics; D005796:Genes; D005975:Glutamate-tRNA Ligase / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D018076:DNA, Complementary; D005656:Fungal Proteins; D000604:Amino Acyl-tRNA Synthetases; D005975:Glutamate-tRNA Ligase; C020659:glutaminyl-tRNA synthetase