title: The structure of threonyl-tRNA synthetase-tRNA(Thr) complex enlightens its repressor activity and reveals an essential zinc ion in the active site.
abstract: E. coli threonyl-tRNA synthetase (ThrRS) is a class II enzyme that represses the translation of its own mRNA. We report the crystal structure at 2.9 A resolution of the complex between tRNA(Thr) and ThrRS, whose structural features reveal novel strategies for providing specificity in tRNA selection. These include an amino-terminal domain containing a novel protein fold that makes minor groove contacts with the tRNA acceptor stem. The enzyme induces a large deformation of the anticodon loop, resulting in an interaction between two adjacent anticodon bases, which accounts for their prominent role in tRNA identity and translational regulation. A zinc ion found in the active site is implicated in amino acid recognition/discrimination.
mesh_terms: D000604:Amino Acyl-tRNA Synthetases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D020134:Catalytic Domain; D019281:Dimerization; D004789:Enzyme Activation / Q000502:physiology; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005816:Genetic Complementation Test; D018716:Molecular Mimicry; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000235:genetics; D012346:RNA, Transfer, Amino Acyl / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015032:Zinc / Q000737:chemistry*