Ribosome run through of the termination codon in the absence of the ribosome releasing factor.

The ribosome releasing factor (RR factor) which releases ribosomes from mRNA at the termination codon has been examined for its effects on the amino acid incorporation programmed by wild type R17 Phage RNA and amB2 R17 RNA. When RR factor was added at the beginning of the incorporation, there was no effect on the initial rate of incorporation but it reduced the final level of incorporation. The reduction of the final level of incorporation was more pronounced for histidine incorporation than for valine incorporation suggesting that the translation of the RNA polymerase cistron was more influenced by RR factor. These experiments were carried out under conditions where no reinitiation of protein synthesis occurred. In the presence of RR factor, suppressor tRNA functioned better for the incorporation of amino acids into proteins with amB2 R17 RNA than did wild type tRNA. No such differential effect of suppressor tRNA was observed in the absence of RR factor. This suggests that the ribosome has to be released from mRNA by RR factor in order for the amber mutation to be effective.