Which ribosomal subunit is targeted by 30S-acting antibiotics such as aminoglycosides and tetracycline?

Which ribosomal subunit is targeted by 30S-acting antibiotics such as aminoglycosides and tetracycline?

• A. 50S
• B. 30S
• C. 70S
• D. 60S

Answer: (B)

Antibiotics that act on the small ribosomal subunit disrupt bacterial protein synthesis by interfering with how mRNA and tRNA are decoded during translation. In bacteria, the ribosome is 70S, made up of a small 30S subunit and a large 50S subunit. Aminoglycosides and tetracycline bind specifically to the 30S subunit. Aminoglycosides cause the ribosome to misread the mRNA, leading to faulty proteins, while tetracycline blocks the A site on the 30S, preventing the correct tRNA from entering and halting elongation. Since these drugs target the small subunit, the correct answer is the small subunit. The large subunit and the entire 70S ribosome aren’t the primary targets of these drugs, and the 60S subunit belongs to eukaryotic ribosomes, not bacterial ones.

Antibiotics that act on the small ribosomal subunit disrupt bacterial protein synthesis by interfering with how mRNA and tRNA are decoded during translation. In bacteria, the ribosome is 70S, made up of a small 30S subunit and a large 50S subunit. Aminoglycosides and tetracycline bind specifically to the 30S subunit. Aminoglycosides cause the ribosome to misread the mRNA, leading to faulty proteins, while tetracycline blocks the A site on the 30S, preventing the correct tRNA from entering and halting elongation. Since these drugs target the small subunit, the correct answer is the small subunit. The large subunit and the entire 70S ribosome aren’t the primary targets of these drugs, and the 60S subunit belongs to eukaryotic ribosomes, not bacterial ones.