An RNA-modifying enzyme that governs both the codon and amino acid specificities of isoleucine tRNA

Mol Cell. 2003 Sep;12(3):689-98. doi: 10.1016/s1097-2765(03)00346-0.


The AUA codon-specific isoleucine tRNA (tRNA(Ile)) in eubacteria has the posttranscriptionally modified nucleoside lysidine (L) at the wobble position of the anticodon (position 34). This modification is a lysine-containing cytidine derivative that converts both the codon specificity of tRNA(Ile) from AUG to AUA and its amino acid specificity from methionine to isoleucine. We identified an essential gene (tilS; tRNA(Ile)-lysidine synthetase) that is responsible for lysidine formation in both Bacillus subtilis and Escherichia coli. The recombinant enzyme complexed specifically with tRNA(Ile) and synthesized L by utilizing ATP and lysine as substrates. The lysidine synthesis of this enzyme was shown to directly convert the amino acid specificity of tRNA(Ile) from methionine to isoleucine in vitro. Partial inactivation of tilS in vivo resulted in an AUA codon-dependent translational defect, which supports the notion that TilS is an RNA-modifying enzyme that plays a critical role in the accurate decoding of genetic information.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence / genetics
  • Amino Acids / metabolism
  • Amino Acyl-tRNA Synthetases / genetics*
  • Amino Acyl-tRNA Synthetases / metabolism
  • Bacillus subtilis / enzymology*
  • Bacillus subtilis / genetics
  • Bacterial Proteins / biosynthesis
  • Bacterial Proteins / genetics
  • Base Sequence / genetics
  • Codon / genetics*
  • Escherichia / enzymology*
  • Escherichia / genetics
  • Escherichia coli Proteins / genetics*
  • Escherichia coli Proteins / metabolism
  • Lysine / analogs & derivatives*
  • Lysine / biosynthesis*
  • Molecular Sequence Data
  • Protein Biosynthesis / genetics
  • Pyrimidine Nucleosides / biosynthesis*
  • RNA / genetics
  • RNA / metabolism
  • RNA Processing, Post-Transcriptional
  • RNA, Transfer, Amino Acyl / genetics
  • RNA, Transfer, Amino Acyl / metabolism*
  • Substrate Specificity


  • Amino Acids
  • Bacterial Proteins
  • Codon
  • Escherichia coli Proteins
  • Pyrimidine Nucleosides
  • RNA, Transfer, Amino Acyl
  • RNA
  • lysidine
  • tRNA(Ile)-lysidine synthetase, Bacillus subtilis
  • Amino Acyl-tRNA Synthetases
  • tilS protein, E coli
  • Lysine