Inhibition of Phe-tRNA binding

Correct answer = D. Because fMet-Phe is made, the ribosomes must be able to complete initia tion, bind Phe-tRNA to the A-site, and use pep tidyltransferase activity to form the first peptide bond. Because the ribosome is not able to pro ceed any further, ribosomal movement (translo cation) is most likely the inhibited step. The ribosome is, therefore, frozen before it reaches the stop codon of this message. 

Another characterization of the binding of peptidyl-tRNA analogs to the ribosome is based on the response to antibiotic inhibitors of peptidyl-transferase activity. Although Oen et al. observed no inhibition of reversible binding of iV-bromoacetyl Phe-tRNA by chloramphenicol, lin-comycin, or streptogramin A, the same antibiotics as well as erythromycin significantly inhibited the binding of p-azido-A-tBoc-Phe-Phe-tRNA. It should be noted, however, that in both cases the antibiotics markedly reduced the extent of the covalent reaction of the aflSnity probes with the ribosome. 

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