Question

The antibiotic 'Puromycin' is structural analog of which of the following amino acyl tRNA?

• A. Alanyl tRNA
• B. Histidyl tRNA
• C. Tyrosnyl tRNA
• D. Prolyl tRNA

Hint:

To remember Puromycin's mechanism:
- It is a Tyrosinyl-tRNA mimic.
- It enters the A-site of the ribosome.
- It causes premature chain termination by covalently binding to the growing peptide.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Translation can be inhibited by specific antibiotics that target the bacterial ribosome.
Some of these inhibitors work by mimicking the molecular structure of translation components.

Step 2: Detailed Explanation:
Puromycin is an aminonucleoside antibiotic produced by the bacterium Streptomyces alboniger.
It acts as a potent inhibitor of translation (protein synthesis) in both prokaryotes and eukaryotes.
Structurally, Puromycin is a molecular mimic of the 3' end of an aminoacyl-tRNA.
Specifically, it resembles the terminal adenosine residue linked to a tyrosine amino acid, making it a structural analog of Tyrosinyl-tRNA (spelled "Tyrosnyl tRNA" in the question).
Because of this structural similarity, Puromycin can enter the A-site of the ribosome during the elongation phase of translation.
The peptidyl transferase enzyme of the ribosome mistakenly transfers the growing polypeptide chain from the P-site to the amino group of Puromycin (acting as a nucleophile).
However, because Puromycin contains an amide linkage instead of the normal, labile ester linkage found in tRNA, the newly formed peptidyl-puromycin cannot undergo translocation.
This causes the premature release of the polypeptide chain, halting translation.

Step 3: Final Answer:
Puromycin is a structural analog of Tyrosinyl-tRNA.