tRNA^Val allows four-way decoding with unmodified uridine at the wobble position in Lactobacillus casei

tRNAs for valine codon decoding in L. casei. (A) Codon–anticodon pairing in valine codon. In E. coli, tRNA^Val(UAC) bearing cmo⁵U at the wobble position decodes all four valine codons, and tRNA^Val(GAC) decodes the GUU and GUC codons. In L. casei, tRNA^Val(UAC) with unmodified or modified U at the wobble position may decode the four valine codons. If tRNA^Und is present in the cells, the tRNA may decode the GUC and GUU codons. (B) Clover-leaf structures of tRNA^Val and tRNA^Und of L. casei. Red letters are anticodon regions. (C) Detection of tRNA^Val and tRNA^Und from L. casei BL23 by northern hybridization. The small RNA fraction of L. casei was separated by 10% PAGE (7 M urea), and the gel was stained with toluidine blue (left panel). The small RNA fraction (lanes: small RNA), native isolated tRNA^Val (lane: native, only in tRNA^Val), and in vitro transcribed tRNA^Val or tRNA^Und (lanes: T7) were separated by 10% PAGE (7 M urea), and the RNAs were transferred to a membrane. Each tRNA was detected using a 5′-³²P-labeled DNA probe with a sequence complementary to tRNA^Val or tRNA^Und. Sequences of the DNA probes for tRNA detection are described in Materials and Methods.