Linezolid, an oxazolidinone antibiotic, inhibits protein synthesis at which specific step that is unique compared to other protein synthesis inhibitors?
- A Inhibits peptidyl transferase activity at the 50S ribosomal subunit during elongation
- B Inhibits translocation by binding EF-G (elongation factor)
- C Binds the 23S rRNA of the 50S subunit and prevents formation of the 70S initiation complex ✓
- D Causes premature chain termination by inserting into the growing peptide chain
Correct answer: C. Binds the 23S rRNA of the 50S subunit and prevents formation of the 70S initiation complex
Explanation
Linezolid binds to domain V of the 23S rRNA component of the 50S ribosomal subunit and prevents the formation of the 70S initiation complex — a step that occurs before elongation begins. This is its unique and defining mechanism: it blocks the ribosome assembly stage at the start of translation initiation, not elongation or translocation. Chloramphenicol inhibits peptidyl transferase during elongation. Fusidic acid inhibits EF-G. Aminoglycosides cause misreading but do not block initiation in this way.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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