Linezolid inhibits bacterial protein synthesis at a step that is different from all other ribosome-targeting antibiotics. Which step does it inhibit?
- A Formation of the 70S initiation complex by blocking 30S–50S subunit joining ✓
- B Peptide bond formation at the peptidyl transferase center of 50S subunit
- C Translocation of the ribosome along mRNA
- D Aminoacyl-tRNA binding to the A-site of the 30S subunit
Correct answer: A. Formation of the 70S initiation complex by blocking 30S–50S subunit joining
Explanation
Linezolid (an oxazolidinone) binds to the 23S rRNA of the 50S subunit at a site that physically obstructs the docking of the 30S initiation complex. This prevents formation of the 70S initiation complex at the very first step of translation — a unique mechanism shared by no other licensed antibiotic. Chloramphenicol inhibits peptidyl transferase; fusidic acid inhibits translocation; tetracyclines block A-site aminoacyl-tRNA binding.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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