title: The 2 A crystal structure of leucyl-tRNA synthetase and its complex with a leucyl-adenylate analogue.
abstract: Leucyl-, isoleucyl- and valyl-tRNA synthetases are closely related large monomeric class I synthetases. Each contains a homologous insertion domain of approximately 200 residues, which is thought to permit them to hydrolyse ('edit') cognate tRNA that has been mischarged with a chemically similar but non-cognate amino acid. We describe the first crystal structure of a leucyl-tRNA synthetase, from the hyperthermophile Thermus thermophilus, at 2.0 A resolution. The overall architecture is similar to that of isoleucyl-tRNA synthetase, except that the putative editing domain is inserted at a different position in the primary structure. This feature is unique to prokaryote-like leucyl-tRNA synthetases, as is the presence of a novel additional flexibly inserted domain. Comparison of native enzyme and complexes with leucine and a leucyl- adenylate analogue shows that binding of the adenosine moiety of leucyl-adenylate causes significant conformational changes in the active site required for amino acid activation and tight binding of the adenylate. These changes are propagated to more distant regions of the enzyme, leading to a significantly more ordered structure ready for the subsequent aminoacylation and/or editing steps.
authors.affiliation: European Molecular Laboratory Biology, Grenoble outstation, c/o ILL, 156X, F-38042 Grenoble, Cedex 9, France. cusack@embl-grenoble.fr
authors.forename: S
authors.initials: S
authors.lastname: Cusack
authors.forename: A
authors.initials: A
authors.lastname: Yaremchuk
authors.forename: M
authors.initials: M
authors.lastname: Tukalo
mesh_terms: D000249:Adenosine Monophosphate / Q000031:analogs & derivatives / Q000737:chemistry / Q000235:genetics; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D001665:Binding Sites; D007935:Leucine-tRNA Ligase / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D011487:Protein Conformation; D016415:Sequence Alignment; D013379:Substrate Specificity; D016963:Thermus thermophilus / Q000737:chemistry / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D000249:Adenosine Monophosphate; D007935:Leucine-tRNA Ligase