Abrin from Abrus precatorius (rosary pea) shares its mechanism of action with ricin from Ricinus communis. Both are classified as Type II ribosome-inactivating proteins (RIPs). What is the cellular mechanism that makes them extremely lethal even in microgram doses?
- A Irreversible inhibition of acetylcholinesterase causing cholinergic crisis
- B A-chain depurinates 28S rRNA at a specific adenine residue, halting protein synthesis ✓
- C Binding to sodium channels causing persistent depolarization
- D Activation of NMDA receptors causing excitotoxic neuronal death
Explanation
Abrin and ricin are Type II RIPs consisting of an A-chain (toxic) and a B-chain (lectin that binds cell-surface galactose residues for endocytosis). Once inside the cell, the A-chain acts as an N-glycosidase, depurinates a specific adenine residue (A4324 in rats) of the 28S rRNA of the 60S ribosomal subunit. This single catalytic event irreversibly inactivates the ribosome, halting all protein synthesis. A single molecule can inactivate thousands of ribosomes, explaining extreme potency. This is not related to acetylcholinesterase (A), sodium channels (C), or NMDA receptors (D).
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.