Question

Many antibiotics work by inhibiting bacterial protein synthesis. Investigators have isolated a promising new compound and wish to determine its mechanism of action. Using a cell-free translation system similar to the ones originally used to deduce the genetic code, the researchers incubate their drug with the synthetic polynucleotide 5'-AUGUUUUUUUUU.

In the absence of the drug, this polynucleotide directs the synthesis of the peptide Met-Phe-Phe-Phe. When the drug is added, only the peptide Met-Phe is produced. Based on this observation, which is most likely the mechanism of action of this potential new antibiotic?

Choose one:
A. It blocks translocation of the large ribosomal subunit, preventing the movement of peptidyl-tRNA from the A site to the P site of the ribosome.
B. It inhibits peptide bond formation.
C. It inhibits the peptidyl transferase activity of the large ribosomal subunit.
D. It blocks the assembly of the initiation complex, including the initiator tRNA and both the large and small ribosomal subunits.
E. It blocks binding of aminoacyl-tRNA to the A site of the ribosome.

Answer 1

The potential new antibiotic most likely inhibits peptide bond formation.

Step-by-step explanation:

The most likely mechanism of action of this potential new antibiotic based on the observation that it only allows the production of the peptide Met-Phe when added to a synthetic polynucleotide is that it inhibits peptide bond formation. The presence of the antibiotic prevents the formation of additional peptide bonds, resulting in the synthesis of only the first two amino acids of the peptide chain.