Ricin A Chain

Ricin is a toxin derived from the castor bean plant. It is being developed as a therapeutic agent to treat cancer, autoimmune diseases and AIDS. But it is also a potential bioterrorist agent. The toxin consists of two chains: the B-chain binds the toxin to cells, then the A chain enters and kills the cell. This is a diagram showing the structure of the A chain, with the active site in red and white. The binding sites of anti-ricin antibodies are yellow and green.