Novel mechanism of post-transcriptional modification of tRNA. Insertion of bases of Q precursors into tRNA by a specific tRNA transglycosylase reaction

J Biol Chem. 1979 Apr 25;254(8):3067-73.


The guanine insertion enzyme isolated from Escherichia coli (tRNA transglycosylase) catalyzed the incorporation of bases of Q (queuosine) precursors into E. coli undermodified tRNAAsn and tRNATyr. These bases of Q precursors were inserted in the first position of the anticodon of tRNASn and tRNATyr, replacing guanine originally located in that position. This is a novel type of post-transcriptional modification, inserting a modified base into the polynucleotide chain by cleavage of the N--C glycoside bond without breakage of the phosphodiester bond. One of the bases of Q precursors, 7-(aminomethyl)-7-deazaguanine, was found in the acid-soluble fraction of E. coli cells, supporting the conclusion that formation of Q, 7-(3,4-trans-4,5-cis-dihydroxy-1-cyclopenten-3-ylaminomethyl)-7-deazaguanosine, in tRNA in vivo actually proceeds by the tRNA transglycosylase reaction.

MeSH terms

  • Escherichia coli / enzymology*
  • Guanine / analogs & derivatives*
  • Guanine / metabolism
  • Kinetics
  • Nucleic Acid Precursors / metabolism
  • Oligoribonucleotides / analysis
  • Protein Biosynthesis
  • RNA, Transfer / metabolism*
  • Transcription, Genetic
  • Transferases / metabolism
  • Tyrosine


  • Nucleic Acid Precursors
  • Oligoribonucleotides
  • Tyrosine
  • Guanine
  • RNA, Transfer
  • Transferases