title: Glutamyl-tRNA(Gln) amidotransferase in Deinococcus radiodurans may be confined to asparagine biosynthesis.
abstract: Asparaginyl-tRNA (Asn-tRNA) and glutaminyl-tRNA (Gln-tRNA) are essential components of protein synthesis. They can be formed by direct acylation by asparaginyl-tRNA synthetase (AsnRS) or glutaminyl-tRNA synthetase (GlnRS). The alternative route involves transamidation of incorrectly charged tRNA. Examination of the preliminary genomic sequence of the radiation-resistant bacterium Deinococcus radiodurans suggests the presence of both direct and indirect routes of Asn-tRNA and Gln-tRNA formation. Biochemical experiments demonstrate the presence of AsnRS and GlnRS, as well as glutamyl-tRNA synthetase (GluRS), a discriminating and a nondiscriminating aspartyl-tRNA synthetase (AspRS). Moreover, both Gln-tRNA and Asn-tRNA transamidation activities are present. Surprisingly, they are catalyzed by a single enzyme encoded by three ORFs orthologous to Bacillus subtilis gatCAB. However, the transamidation route to Gln-tRNA formation is idled by the inability of the discriminating D. radiodurans GluRS to produce the required mischarged Glu-tRNAGln substrate. The presence of apparently redundant complete routes to Asn-tRNA formation, combined with the absence from the D. radiodurans genome of genes encoding tRNA-independent asparagine synthetase and the lack of this enzyme in D. radiodurans extracts, suggests that the gatCAB genes may be responsible for biosynthesis of asparagine in this asparagine prototroph.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520-8114, USA.
authors.forename: A W
authors.initials: AW
authors.lastname: Curnow
authors.forename: D L
authors.initials: DL
authors.lastname: Tumbula
authors.forename: J T
authors.initials: JT
authors.lastname: Pelaschier
authors.forename: B
authors.initials: B
authors.lastname: Min
authors.forename: D
authors.initials: D
authors.lastname: Söll
mesh_terms: D000215:Acylation; D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism*; D001216:Asparagine / Q000096:biosynthesis*; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D016680:Genome, Bacterial; D005975:Glutamate-tRNA Ligase / Q000378:metabolism; D006095:Gram-Positive Cocci / Q000201:enzymology* / Q000235:genetics; D007700:Kinetics; D008956:Models, Chemical; D019884:Nitrogenous Group Transferases / Q000378:metabolism*; D016366:Open Reading Frames
chemical_list: D004269:DNA, Bacterial; D001216:Asparagine; D019884:Nitrogenous Group Transferases; C047694:glutamyl-tRNA(Gln) amidotransferase; D000604:Amino Acyl-tRNA Synthetases; D005975:Glutamate-tRNA Ligase; C020659:glutaminyl-tRNA synthetase