Which of the following best describes the mechanism of action of aminoglycosides such as gentamicin?
- A Binding the 50S ribosomal subunit and blocking translocation
- B Binding the 30S ribosomal subunit and causing misreading of mRNA codons ✓
- C Inhibiting the enzyme DNA gyrase in replicating bacteria
- D Blocking peptidyl transferase at the 50S subunit
Correct answer: B. Binding the 30S ribosomal subunit and causing misreading of mRNA codons
Explanation
Aminoglycosides bind irreversibly to the 30S ribosomal subunit, specifically the 16S rRNA component of the 30S decoding region, causing misreading of mRNA and incorporation of wrong amino acids, along with premature termination. Option A describes macrolides, which block translocation at the 50S subunit. Option D describes chloramphenicol. Option C describes fluoroquinolones. The bactericidal, concentration-dependent killing of aminoglycosides follows from this irreversible 30S binding.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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