Linezolid inhibits bacterial protein synthesis at which specific step, making it unique among clinical protein synthesis inhibitors?
- A Inhibits formation of the 70S initiation complex by binding 23S rRNA ✓
- B Blocks peptidyl transferase activity at the 50S subunit during elongation
- C Causes misreading of mRNA codons at the 30S A-site
- D Blocks translocation of the ribosome along mRNA
Correct answer: A. Inhibits formation of the 70S initiation complex by binding 23S rRNA
Explanation
Linezolid (an oxazolidinone) uniquely inhibits the initiation step of bacterial protein synthesis by binding to 23S rRNA of the 50S subunit and preventing formation of the 70S initiation complex; this is a mechanism not shared by any other clinical antibiotic class, explaining the lack of cross-resistance. Chloramphenicol inhibits peptidyl transferase during elongation. Aminoglycosides cause codon misreading at the 30S A-site. Fusidic acid blocks translocation.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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