Ricin (Ric)

Ricin is a highly toxic, naturally occurring lectin (a carbohydrate-binding protein) produced in the seeds of the castor oil plant Ricinus communis. A dose the size of a few grains of table salt can kill an adult human. Ricin is poisonous if inhaled, injected, or ingested; it acts as a toxin by inhibiting protein synthesis. It prevents cells from assembling various amino acids into proteins according to the messages it receives from messenger RNA in a process conducted by the cell's ribosome (the protein-making machinery)—that is, the most basic level of cell metabolism, essential to all living cells and thus to life itself. Ricin is resistant, but not impervious, to digestion by peptidases. By ingestion, the pathology of ricin is largely restricted to the gastrointestinal tract, where it may cause mucosal injuries; with appropriate treatment, most patients will make a full recovery.