Linezolid differs mechanistically from all other protein synthesis inhibitors in that it:
- A Inhibits the 30S ribosomal subunit and causes misreading of mRNA
- B Inhibits translocation by blocking the EF-G binding site on the 50S subunit
- C Binds the 23S rRNA of the 50S subunit to prevent formation of the 70S initiation complex ✓
- D Binds 16S rRNA causing conformational change that prevents tRNA binding
Correct answer: C. Binds the 23S rRNA of the 50S subunit to prevent formation of the 70S initiation complex
Explanation
Linezolid (an oxazolidinone) uniquely targets the 23S rRNA component of the 50S subunit, preventing formation of the 70S initiation complex — the very first step of translation. This is distinct from chloramphenicol and macrolides which block peptidyl transferase and translocation respectively after the initiation complex forms. This novel target explains lack of cross-resistance with other protein synthesis inhibitors.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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