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?

Answer 1

Answer:

The correct answer is "It blocks translocation of the large ribosomal subunit, preventing the movement of peptidyl-tRNA from the A (acceptor) site to the P (peptidyl) site of the ribosome".

Explanation:

Many antibiotics work by inhibiting bacterial protein synthesis, and they act at different levels of the synthesis process. The mechanism of action of antibiotics could be assessed using different strategies on the laboratory. In this case an antibiotic with the synthetic polynucleotide 5’-AUGUUUUUUUUU resulting in disrupting peptide synthesis to Met-Phe would block translocation of the large ribosomal subunit, preventing the movement of peptidyl-tRNA from the A (acceptor) site to the P (peptidyl) site of the ribosome. The A site is the point of entry of the tRNA and where the first and second amino acid are added, whereas the P site is where the whole polypeptide is synthesized. This antiobiotic does not allow that protein synthesis continues to the P site of the ribosome, therefore the proteins synthesized only have two amino acids.