title: Misactivated amino acids translocate at similar rates across surface of a tRNA synthetase.
abstract: Certain aminoacyl-tRNA synthetases have a second active site that destroys (by hydrolysis) errors of amino acid activation. For example, isoleucyl-tRNA synthetase misactivates valine (to produce valyl adenylate or Val-tRNA(Ile)) at its active site. The misactivated amino acid is then translocated to an editing site located >25 A away. The role of the misactivated amino acid in determining the rate of translocation is not known. Valyl-tRNA synthetase, a close homolog of isoleucyl-tRNA synthetase, misactivates threonine, alpha-aminobutyrate, and cysteine. In this paper, we use a recently developed fluorescence-energy-transfer assay to study translocation of misactivated threonine, alpha-aminobutyrate, and cysteine. Although their rates of misactivation are clearly distinct, their rates of translocation are similar. Thus, the rate of translocation is independent of the nature of the misactivated amino acid. This result suggests that the misactivated amino acid per se has little or no role in directing translocation.
authors.affiliation: The Skaggs Institute for Chemical Biology, The Scripps Research Institute, Beckman Center, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: T K
authors.initials: TK
authors.lastname: Nomanbhoy
authors.forename: P R
authors.initials: PR
authors.lastname: Schimmel
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000613:Aminobutyrates / Q000378:metabolism; D001665:Binding Sites; D003001:Cloning, Molecular; D003545:Cysteine / Q000378:metabolism; D004735:Energy Transfer; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D007533:Isoleucine-tRNA Ligase / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D016366:Open Reading Frames; D011487:Protein Conformation; D017393:RNA Editing; D012366:RNA, Transfer, Val / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013912:Threonine / Q000378:metabolism; D014637:Valine-tRNA Ligase / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D000613:Aminobutyrates; D012366:RNA, Transfer, Val; D011994:Recombinant Proteins; D013912:Threonine; C012223:alpha-aminobutyric acid; D007533:Isoleucine-tRNA Ligase; D014637:Valine-tRNA Ligase; D003545:Cysteine