Erythromycin and Chloramphenicol (option 1) are the antibiotics that inhibit translation by binding to the 50S ribosomal subunit.

Question Breakdown

This question tests knowledge of antibiotic mechanisms in microbiology, focusing on how certain drugs target bacterial protein synthesis at the ribosome’s large subunit.

Option Analysis

• Option 1: Erythromycin, Chloramphenicol: Both bind the 50S subunit—erythromycin blocks the exit tunnel to halt elongation, while chloramphenicol inhibits peptidyl transferase activity. Correct choice.

• Option 2: Kanamycin, Neomycin: Aminoglycosides that bind the 30S subunit, causing mRNA misreading and inhibiting initiation. Incorrect.​

• Option 3: Vancomycin, Cycloserine: Cell wall synthesis inhibitors—vancomycin blocks peptidoglycan cross-linking; cycloserine disrupts precursor formation. No ribosomal action.​

• Option 4: Kanamycin, Vancomycin: Kanamycin targets 30S; vancomycin affects cell walls. Mixed targets, incorrect.

Introduction to 50S-Targeting Antibiotics

Antibiotics inhibit translation 50S ribosomal subunit like erythromycin and chloramphenicol by binding its peptidyl transferase center or nascent peptide tunnel, stopping bacterial protein synthesis.

These drugs are vital in microbiology for selective prokaryotic targeting, sparing eukaryotic 60S subunits.​

Mechanism of Key Antibiotics

Erythromycin, a macrolide, binds 50S near 23S rRNA to block elongation. Chloramphenicol overlaps at the A-site, preventing peptide bond formation.

Both disrupt 50S maturation indirectly in some cases.​

Comparison of Options

Relevance for Life Sciences Exams

In GATE or similar exams, recall 50S binders (macrolides, chloramphenicol, lincosamides) versus 30S (aminoglycosides, tetracyclines).​

This aligns with your molecular biology focus, emphasizing ribosomal targets in antimicrobial therapy.​