title: Crystal structure of glycyl-tRNA synthetase from Thermus thermophilus.
abstract: The sequence and crystal structure at 2.75 A resolution of the homodimeric glycyl-tRNA synthetase from Thermus thermophilus, the first representative of the last unknown class II synthetase subgroup, have been determined. The three class II synthetase sequence motifs are present but the structure was essential for identification of motif 1, which does not possess the proline previously believed to be an essential class II invariant. Nevertheless, crucial contacts with the active site of the other monomer involving motif 1 are conserved and a more comprehensive description of class II now becomes possible. Each monomer consists of an active site strongly resembling that of the aspartyl and seryl enzymes, a C-terminal anticodon recognition domain of 100 residues and a third domain unusually inserted between motifs 1 and 2 almost certainly interacting with the acceptor arm of tRNA(Gly). The C-terminal domain has a novel five-stranded parallel-antiparallel beta-sheet structure with three surrounding helices. The active site residues most probably responsible for substrate recognition, in particular in the Gly binding pocket, can be identified by inference from aspartyl-tRNA synthetase due to the conserved nature of the class II active site.
authors.affiliation: Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, BP 163, Illkirch, France.
authors.forename: D T
authors.initials: DT
authors.lastname: Logan
authors.forename: M H
authors.initials: MH
authors.lastname: Mazauric
authors.forename: D
authors.initials: D
authors.lastname: Kern
authors.forename: D
authors.initials: D
authors.lastname: Moras
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray / Q000379:methods; D015342:DNA Probes; D005798:Genes, Bacterial; D006032:Glycine-tRNA Ligase / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D016963:Thermus thermophilus / Q000201:enzymology*
chemical_list: D015342:DNA Probes; D046911:Macromolecular Substances; D006032:Glycine-tRNA Ligase