A eubacterial Mycobacterium tuberculosis tRNA synthetase is eukaryote-like and resistant to a eubacterial-specific antisynthetase drug

Biochemistry. 1996 Aug 6;35(31):9995-10003. doi: 10.1021/bi9603027.


We report here the cloning and primary structure of Mycobacterium tuberculosis isoleucyl-tRNA synthetase. The predicted 1035-amino acid protein is significantly more similar in sequence to eukaryote cytoplasmic than to other eubacterial isoleucyl-tRNA synthetases. This similarity correlates with the enzyme being resistant to pseudomonic acid A, a potent inhibitor of Escherichia coli and other eubacterial isoleucyl-tRNA synthetases, but not of eukaryote cytoplasmic enzymes. Consistent with its eukaryote-like features, and unlike E. coli isoleucyl-tRNA synthetase, the M. tuberculosis enzyme charged yeast isoleucine tRNA. In spite of these eukaryote-like features, M. tuberculosis isoleucyl-tRNA synthetase exhibited highly specific cross-species aminoacylation, as demonstrated by its ability to complement isoleucyl-tRNA synthetase-deficient mutants of E. coli. When introduced into a pseudomonic acid-sensitive wild-type strain of E. coli, the M. tuberculosis enzyme conferred trans-dominant resistance to the drug. The results demonstrate that the sequence of a tRNA synthetase could have predictive value with respect to the interaction of that synthetase with a specific inhibitor. The results also demonstrate that mobilization of a pathogen's gene for a drug-resistant protein target can spread resistance to other, normally drug-sensitive pathogens infecting the same host.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Archaea / enzymology*
  • Archaea / genetics
  • Base Sequence
  • Cloning, Molecular
  • DNA Primers
  • Escherichia coli
  • Eubacterium / enzymology
  • Eubacterium / genetics
  • Isoleucine-tRNA Ligase / biosynthesis
  • Isoleucine-tRNA Ligase / chemistry*
  • Isoleucine-tRNA Ligase / metabolism*
  • Kinetics
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Mycobacterium tuberculosis / enzymology*
  • Mycobacterium tuberculosis / genetics
  • Phylogeny
  • Polymerase Chain Reaction
  • Protein Folding
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Sequence Homology, Amino Acid


  • DNA Primers
  • Recombinant Proteins
  • Isoleucine-tRNA Ligase