title: The crystal structure of asparaginyl-tRNA synthetase from Thermus thermophilus and its complexes with ATP and asparaginyl-adenylate: the mechanism of discrimination between asparagine and aspartic acid.
abstract: The crystal structure of Thermus thermophilus asparaginyl-tRNA synthetase has been solved by multiple isomorphous replacement and refined at 2.6 A resolution. This is the last of the three class IIb aminoacyl-tRNA synthetase structures to be determined. As expected from primary sequence comparisons, there are remarkable similarities between the tertiary structures of asparaginyl-tRNA synthetase and aspartyl-tRNA synthetase, and most of the active site residues are identical except for three key differences. The structure at 2.65 A of asparaginyl-tRNA synthetase complexed with a non-hydrolysable analogue of asparaginyl-adenylate permits a detailed explanation of how these three differences allow each enzyme to discriminate between their respective and very similar amino acid substrates, asparagine and aspartic acid. In addition, a structure of the complex of asparaginyl-tRNA synthetase with ATP shows exactly the same configuration of three divalent cations as previously observed in the seryl-tRNA synthetase-ATP complex, showing that this a general feature of class II synthetases. The structural similarity of asparaginyl- and aspartyl-tRNA synthetases as well as that of both enzymes to the ammonia-dependent asparagine synthetase suggests that these three enzymes have evolved relatively recently from a common ancestor.
authors.affiliation: European Molecular Biology Laboratory, Grenoble Outstation, Grenoble, France.
authors.forename: C
authors.initials: C
authors.lastname: Berthet-Colominas
authors.forename: L
authors.initials: L
authors.lastname: Seignovert
authors.forename: M
authors.initials: M
authors.lastname: Härtlein
authors.forename: M
authors.initials: M
authors.lastname: Grotli
authors.forename: S
authors.initials: S
authors.lastname: Cusack
authors.forename: R
authors.initials: R
authors.lastname: Leberman
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D000604:Amino Acyl-tRNA Synthetases / Q000737:chemistry* / Q000378:metabolism; D001216:Asparagine / Q000737:chemistry* / Q000378:metabolism; D001226:Aspartate-tRNA Ligase; D001224:Aspartic Acid / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D019281:Dimerization; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012346:RNA, Transfer, Amino Acyl; D017386:Sequence Homology, Amino Acid; D016963:Thermus thermophilus / Q000201:enzymology*
chemical_list: D012346:RNA, Transfer, Amino Acyl; D001224:Aspartic Acid; D001216:Asparagine; D000255:Adenosine Triphosphate; D000604:Amino Acyl-tRNA Synthetases; D001226:Aspartate-tRNA Ligase; C029194:asparaginyl-tRNA synthetase