title: Errors from selective disruption of the editing center in a tRNA synthetase.
abstract: Some aminoacyl-tRNA synthetases have two catalytic centers that together achieve fine-structure discrimination of closely similar amino acids. The role of tRNA is to stimulate translocation of a misactivated amino acid from the active site to the editing site where the misactivated substrate is eliminated by hydrolysis. Using isoleucyl-tRNA synthetase as an example, we placed mutations in the catalytic center for editing at residues strongly conserved from bacteria to humans. A particular single substitution and one double substitution resulted in production of mischarged tRNA, by interfering specifically with the chemical step of hydrolytic editing. The substitutions affected neither amino acid activation nor aminoacylation, with the cognate amino acid. Thus, because of the demonstrated functional independence of the two catalytic sites, errors of aminoacylation can be generated by selective mutations in the center for editing.
authors.affiliation: The Skaggs Institute for Chemical Biology and Departments of Molecular Biology and Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
authors.forename: T L
authors.initials: TL
authors.lastname: Hendrickson
authors.forename: T K
authors.initials: TK
authors.lastname: Nomanbhoy
authors.forename: P
authors.initials: P
authors.lastname: Schimmel
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D001692:Biological Transport; D004926:Escherichia coli; D007533:Isoleucine-tRNA Ligase / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017354:Point Mutation; D017393:RNA Editing / Q000502:physiology*; D012343:RNA, Transfer / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D016963:Thermus thermophilus / Q000201:enzymology; D014633:Valine / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D012343:RNA, Transfer; D007533:Isoleucine-tRNA Ligase; D014633:Valine