Simplified organization of the 3 operons containing the Ile-tRNA source of Ile-tRF-5X.

isoleucine(Ile)-tRNA (GAT = anticodon) and alanine(Ala)-tRNA (TGC = anticodon) genes are found in the rrnA, rrnD and rrnH operons of E. coli K-12 genome. The Ile and Ala tRNAs are flanked by the 16S and 23s ribosomal RNAs (rRNAs). ileT, ileU, ileV genes all produce Ile(GAU)-tRNA. alaT, alaU, alaV genes all produce Ala(UGC)-tRNA. This diagram represents the three transcription units in one panel, under which the genomic sequence of Ile-tRNA and its mature sequence are presented. The 13-nt sequence in red represents Ile-tRF-5X, with its predicted secondary structure. The diagram does not show the endo and exonucleases involved in the maturation at each stage. The ribonuclease(s) involved in the cleavage of Ile-tRF-5X 3’ end have yet to be identified. Str, strain; substr, substrain; tRNA, transfer RNA.