Which antibiotic binds to DNA and induces strand breaks by generating hydroxyl radicals, thereby cutting the DNA?

Introduction / Context:Some chemotherapeutic antibiotics act directly on DNA structure, producing breaks that halt replication and transcription. Bleomycin is a classic example used in oncology. Distinguishing it from antibiotics that target ribosomes or glycosylation highlights different mechanisms of action.

Given Data / Assumptions:

• We are comparing mechanisms: DNA cleavage vs. protein synthesis inhibition vs. glycosylation interference.
• Hydroxyl radical formation is a key clue.
• Agents listed: bleomycin (antitumor), erythromycin (macrolide), tunicamycin (glycosylation inhibitor).

Concept / Approach:Bleomycin chelates metal ions (often Fe2+) and, in the presence of oxygen, generates reactive oxygen species including hydroxyl radicals. These radicals induce single- and double-strand DNA breaks. By contrast, erythromycin binds the 50S ribosomal subunit to inhibit peptide elongation, and tunicamycin blocks N-linked glycosylation in the endoplasmic reticulum by inhibiting UDP-N-acetylglucosamine: dolichol phosphate N-acetylglucosamine-1-phosphate transferase. Neither erythromycin nor tunicamycin directly cleaves DNA via hydroxyl radicals.

Step-by-Step Solution:Identify the mechanism described: DNA binding and radical-mediated cleavage.Match to drug known for ROS-dependent DNA strand scission: bleomycin.Exclude drugs with ribosomal or glycosylation targets.Select bleomycin as the correct answer.

Verification / Alternative check:Clinical pharmacology references report pulmonary toxicity as a notable bleomycin adverse effect, consistent with oxidative mechanisms, and its inclusion in combination cancer regimens (e.g., ABVD for Hodgkin lymphoma).

Why Other Options Are Wrong:Erythromycin: protein synthesis inhibitor; does not cleave DNA.Tunicamycin: disrupts glycoprotein biosynthesis; no DNA cutting activity.All of these: incorrect because only bleomycin matches the described mechanism.

Common Pitfalls:Assuming all “antibiotics” target DNA. Many act on ribosomes, cell walls, or metabolic enzymes.

Final Answer:Bleomycin