Which class targets the 50S ribosomal subunit?

Which class targets the 50S ribosomal subunit?

• A. Macrolides
• B. Tetracyclines
• C. Aminoglycosides
• D. Fluoroquinolones

Answer: (A)

Targeting the 50S ribosomal subunit is what macrolides do. They bind to the 50S ribosomal subunit, interacting with the 23S rRNA, and block the movement of the ribosome along mRNA (translocation). This stops protein synthesis in bacteria, leading to a bacteriostatic effect. In contrast, antibiotics that target the 30S subunit—like tetracyclines, which block tRNA from entering the A site, and aminoglycosides, which cause misreading of the mRNA—affect translation at different steps. Fluoroquinolones work on DNA rather than the ribosome, inhibiting DNA gyrase and topoisomerase IV.

Targeting the 50S ribosomal subunit is what macrolides do. They bind to the 50S ribosomal subunit, interacting with the 23S rRNA, and block the movement of the ribosome along mRNA (translocation). This stops protein synthesis in bacteria, leading to a bacteriostatic effect.

In contrast, antibiotics that target the 30S subunit—like tetracyclines, which block tRNA from entering the A site, and aminoglycosides, which cause misreading of the mRNA—affect translation at different steps. Fluoroquinolones work on DNA rather than the ribosome, inhibiting DNA gyrase and topoisomerase IV.