title: Functional and crystal structure analysis of active site adaptations of a potent anti-angiogenic human tRNA synthetase.
abstract: Higher eukaryote tRNA synthetases have expanded functions that come from enlarged, more differentiated structures that were adapted to fit aminoacylation function. How those adaptations affect catalytic mechanisms is not known. Presented here is the structure of a catalytically active natural splice variant of human tryptophanyl-tRNA synthetase (TrpRS) that is a potent angiostatic factor. This and related structures suggest that a eukaryote-specific N-terminal extension of the core enzyme changed substrate recognition by forming an active site cap. At the junction of the extension and core catalytic unit, an arginine is recruited to replace a missing landmark lysine almost 200 residues away. Mutagenesis, rapid kinetic, and substrate binding studies support the functional significance of the cap and arginine recruitment. Thus, the enzyme function of human TrpRS has switched more to the N terminus of the sequence. This switch has the effect of creating selective pressure to retain the N-terminal extension for functional expansion.
authors.affiliation: The Scripps Research Institute, BCC-379, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA. xlyang@scripps.edu
authors.forename: Xiang-Lei
authors.initials: XL
authors.lastname: Yang
authors.forename: Min
authors.initials: M
authors.lastname: Guo
authors.forename: Mili
authors.initials: M
authors.lastname: Kapoor
authors.forename: Karla L
authors.initials: KL
authors.lastname: Ewalt
authors.forename: Francella J
authors.initials: FJ
authors.lastname: Otero
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Skene
authors.forename: Duncan E
authors.initials: DE
authors.lastname: McRee
authors.forename: Paul
authors.initials: P
authors.lastname: Schimmel
mesh_terms: D000107:Acetylation; D000595:Amino Acid Sequence; D020533:Angiogenesis Inhibitors / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D001665:Binding Sites; D018360:Crystallography, X-Ray; D001411:Geobacillus stearothermophilus / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D012326:RNA Splicing; D013379:Substrate Specificity; D014369:Tryptophan-tRNA Ligase / Q000737:chemistry* / Q000235:genetics
chemical_list: D020533:Angiogenesis Inhibitors; D001426:Bacterial Proteins; D014369:Tryptophan-tRNA Ligase