A class of antibiotics inhibits the 50S ribosomal subunit by blocking peptidyl transferase activity, causing premature chain termination when they insert into the A site and accept the growing peptide chain from P-site tRNA (producing truncated peptidyl-aminoacyl adducts). This describes the mechanism of:
- A Chloramphenicol
- B Linezolid
- C Fusidic acid
- D Puromycin ✓
Explanation
Puromycin structurally mimics aminoacyl-tRNA at the 3' end; it enters the A site of the ribosome, the growing peptide is transferred to it by peptidyl transferase, but because puromycin has no 3'-OH for further elongation, translation terminates prematurely and the truncated peptidyl-puromycin adduct is released. This occurs in both prokaryotes and eukaryotes (unlike most antibiotics). Chloramphenicol blocks peptidyl transferase on the 50S but does not itself accept the peptide chain. Linezolid blocks initiation by preventing fMet-tRNA binding. Fusidic acid inhibits EF-G (translocation).
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.