Linezolid exerts its antibacterial effect by inhibiting bacterial protein synthesis at which step?

• A Binding to the 30S subunit, blocking peptide elongation
• B Blocking translocation of peptidyl-tRNA from A to P site
• C Cleaving aminoacyl-tRNA from the 50S A site
• D Inhibiting formation of the 70S initiation complex (30S–50S union) ✓

Explanation

Linezolid (an oxazolidinone) binds to the 23S rRNA of the 50S subunit at a site that prevents the 30S–50S initiation complex from forming, thereby inhibiting protein synthesis at the initiation stage—a unique mechanism that explains the lack of cross-resistance with most other antibiotic classes. Aminoglycosides bind the 30S subunit and cause misreading; macrolides block translocation; chloramphenicol blocks peptidyl transferase.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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