Abrus precatorius (rosary pea) seeds are among the most potent plant toxins. The mechanism by which abrin causes cell death is:
- A Inhibition of DNA topoisomerase II, preventing cell division
- B Depurination of 28S ribosomal RNA, halting protein synthesis ✓
- C Cross-linking of cellular proteins through its lectin A-chain
- D Activation of caspase-8 directly without ribosomal involvement
Correct answer: B. Depurination of 28S ribosomal RNA, halting protein synthesis
Explanation
Abrin is a type II ribosome-inactivating protein (RIP) structurally similar to ricin. The B-chain binds cell surface galactose residues and facilitates entry; the A-chain enzymatically depurinates a specific adenine residue on 28S rRNA at the sarcin-ricin loop, irreversibly inhibiting ribosome function and halting protein synthesis, leading to cell death. This mechanism is identical to ricin. The toxin does not act through topoisomerase inhibition, protein cross-linking, or direct caspase activation.
Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.