Bacillus subtilis tRNA(Pro) with the anticodon mo5UGG can recognize the codon CCC.

In Bacillus subtilis, four codons, CCU, CCC, CCA, and CCG, are used for proline. There exists, however, only one proline-specific tRNA having the anticodon mo(5)UGG. Here, we found that this tRNA(Pro)(mo(5)UGG) can read not only the codons CCA, CCG and CCU but also CCC, using an in vitro assay system. This means that the first nucleoside of its anticodon, 5-methoxyuridine (mo(5)U), recognizes A, G, U and C. On the other hand, it was reported that mo(5)U at the first position of the anticodon of tRNA(Val)(mo(5)UAC) can recognize A, G, and U but not C. A comparison of the structure of the anticodon stem and loop of tRNA(Pro)(mo(5)UGG) with those of other tRNAs containing mo(5)U at the first positions of the anticodons suggests that a modification of nucleoside 32 to pseudouridine (Psi) enables tRNA(Pro)(mo(5)UGG) to read the CCC codon.