Question

Which one or more of the following statements correctly describe(s) the changes upon the addition of puromycin during eukaryotic translation?

• A. ( Puromycin resembles aminoacyl end of the charged tRNA. )
• B. ( Puromycin occupies the A site of the translating ribosomes. )
• C. ( Puromycin occupies the P site of the translating ribosomes. )
• D. ( Puromycin occupies the E site of the translating ribosomes. )

Hint:

Puromycin is often used in biochemical experiments to study the mechanics of translation and to induce controlled premature termination of peptide synthesis.

Answer 1

The Correct Option is A

Detailed Analysis of Each Statement: (A) Resemblance to aminoacyl end of tRNA: Correct. Puromycin structurally mimics the aminoacyl end of tRNA. This resemblance allows it to bind to the A site of the ribosome and participate in peptide bond formation but leads to premature chain termination because it cannot properly engage in subsequent translocation steps. (B) Occupancy of the A site: Correct. Puromycin enters the A site of ribosomes where aminoacyl-tRNAs normally bind and participate in peptide bond formation, which disrupts normal protein synthesis by causing premature termination. (C) Occupancy of the P site: Incorrect. While puromycin interacts with the ribosome at the A site, it does not occupy the P site where peptidyl-tRNA is located during translation. (D) Occupancy of the E site: Incorrect. The E (exit) site is typically where deacylated tRNAs reside before exiting the ribosome, and puromycin does not function at this site. Conclusion:
Thus, statements (A) and (B) correctly describe the action of puromycin in the translation process, highlighting its unique role as a translation terminator by mimicking the crucial components of the translation machinery.