title: Structure of nondiscriminating glutamyl-tRNA synthetase from Thermotoga maritima.
abstract: Aminoacyl-tRNA synthetases produce aminoacyl-tRNAs from the substrate tRNA and its cognate amino acid with the aid of ATP. Two types of glutamyl-tRNA synthetase (GluRS) have been discovered: discriminating GluRS (D-GluRS) and nondiscriminating GluRS (ND-GluRS). D-GluRS glutamylates tRNA(Glu) only, while ND-GluRS glutamylates both tRNA(Glu) and tRNA(Gln). ND-GluRS produces the intermediate Glu-tRNA(Gln), which is converted to Gln-tRNA(Gln) by Glu-tRNA(Gln) amidotransferase. Two GluRS homologues from Thermotoga maritima, TM1875 and TM1351, have been biochemically characterized and it has been clarified that only TM1875 functions as an ND-GluRS. Furthermore, the crystal structure of the T. maritima ND-GluRS, TM1875, was determined in complex with a Glu-AMP analogue at 2.0 A resolution. The T. maritima ND-GluRS contains a characteristic structure in the connective-peptide domain, which is inserted into the catalytic Rossmann-fold domain. The glutamylation ability of tRNA(Gln) by ND-GluRS was measured in the presence of the bacterial Glu-tRNA(Gln) amidotransferase GatCAB. Interestingly, the glutamylation efficiency was not affected even in the presence of excess GatCAB. Therefore, GluRS avoids competition with GatCAB and glutamylates tRNA(Gln).
authors.affiliation: Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Takuhiro
authors.initials: T
authors.lastname: Ito
authors.forename: Noriko
authors.initials: N
authors.lastname: Kiyasu
authors.forename: Risa
authors.initials: R
authors.lastname: Matsunaga
authors.forename: Seizo
authors.initials: S
authors.lastname: Takahashi
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Yokoyama
mesh_terms: D000595:Amino Acid Sequence; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D005975:Glutamate-tRNA Ligase / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D016415:Sequence Alignment; D040681:Structural Homology, Protein; D020124:Thermotoga maritima / Q000201:enzymology*
chemical_list: D012346:RNA, Transfer, Amino Acyl; D005975:Glutamate-tRNA Ligase