EFFECT OF BACILLUS-SUBTILIS TRNA(TRP) ON READTHROUGH RATE AT AN OPAL UGA CODON

Bacillus subtilis has been thought to have a high readthrough rate at the UGA stop codon because no opal suppressor tRNA has been isolated s o far [Lovett ct al, (1991) J, Bacteriol, 173, 1810-1812], To examine whether a tRNA(TrP) which We have characterized [Matsugi ct al, (1992) Nucleic Acids Res. 20, 3514] has the ability to read the UGA codon, i n vitro translation was performed with a synthetic mRNA containing a t est codon, UGA, UAG, UAA, or UGG, in a reading frame, Addition of Trp- tRNA(Trp) to the system significantly increased the readthrough rate o nly in the case of UGA. This suggests that this tRNA(Trp) has a dual r ecognition pattern in B, subtilis, i.e., for the canonical tryptophan codon and for readthrough at the UGA stop codon.