Peptide chain termination. V. The role of release factors in mRNA terminator codon recognition.

The protein release factors, R1 and R2, bind to ribosomes in response to specific terminator codons (R1 to UAA or UAG, R2 to UAA or UGA). In reactions containing ribosomes, the tritiated oligonucleotide UA[(3)H](A)(2) is retained on nitrocellulose filters in response to either R1 or R2, and UA[(3)H]G in response to R1. These results indicate that an R.terminator codon.70S ribosome intermediate occurs during terminator codon recognition and suggest that protein release factors R1 and R2 recognize terminator codons.