title: The bacterial YbaK protein is a Cys-tRNAPro and Cys-tRNA Cys deacylase.
abstract: Bacterial prolyl-tRNA synthetases and some smaller paralogs, YbaK and ProX, can hydrolyze misacylated Cys-tRNA Pro or Ala-tRNA Pro. To assess the significance of this quality control editing reaction in vivo, we tested Escherichia coli ybaK for its ability to suppress the E. coli thymidylate synthase thyA:146CCA missense mutant strain, which requires Cys-tRNA(Pro) for growth in the absence of thymine. Missense suppression was observed in a ybaK deletion background, suggesting that YbaK functions as a Cys-tRNA Pro deacylase in vivo. In vitro studies with the full set of 20 E. coli aminoacyl-tRNAs revealed that the Haemophilus influenzae and E. coli YbaK proteins are moderately general aminoacyl-tRNA deacylases that preferentially hydrolyze Cys-tRNA Pro and Cys-tRNA Cys and are also weak deacylases that cleave Gly-tRNA, Ala-tRNA, Ser-tRNA, Pro-tRNA, and Met-tRNA. The ProX protein acted as an aminoacyl-tRNA deacylase that cleaves preferentially Ala-tRNA and Gly-tRNA. The potential of H. influenzae YbaK to hydrolyze in vivo correctly charged Cys-tRNA Cys was tested in E. coli strain X2913 (ybaK+). Overexpression of H. influenzae ybaK decreased the in vivo ratio of Cys-tRNA Cys to tRNA Cys from 65 to 35% and reduced the growth rate of strain X2913 by 30% in LB medium. These data suggest that YbaK-mediated hydrolysis of aminoacyl-tRNA can influence cell growth.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8114, USA.
authors.forename: Benfang
authors.initials: B
authors.lastname: Ruan
authors.forename: Dieter
authors.initials: D
authors.lastname: Söll
mesh_terms: D000604:Amino Acyl-tRNA Synthetases / Q000235:genetics / Q000378:metabolism; D019881:Aminoacyltransferases / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D047991:Acetoanaerobium sticklandii / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D006193:Haemophilus influenzae / Q000235:genetics*; D006868:Hydrolysis; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D012346:RNA, Transfer, Amino Acyl; C481278:YbaK protein, Haemophilus influenzae; D019881:Aminoacyltransferases; D000604:Amino Acyl-tRNA Synthetases; C100134:prolyl T RNA synthetase