title: Novel mechanism of post-transcriptional modification of tRNA. Insertion of bases of Q precursors into tRNA by a specific tRNA transglycosylase reaction.
abstract: 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: D004926:Escherichia coli / Q000201:enzymology*; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism; D007700:Kinetics; D009694:Nucleic Acid Precursors / Q000378:metabolism; D009843:Oligoribonucleotides / Q000032:analysis; D014176:Protein Biosynthesis; D012343:RNA, Transfer / Q000378:metabolism*; D014158:Transcription, Genetic; D014166:Transferases / Q000378:metabolism; D014443:Tyrosine
chemical_list: D009694:Nucleic Acid Precursors; D009843:Oligoribonucleotides; D014443:Tyrosine; D006147:Guanine; D012343:RNA, Transfer; D014166:Transferases