Plant toxic proteins and their current significance for warfare and medicine

Abrin, ricin, viscumin, modeccin, and volkensin are very potent toxins derived from plants. They are glycoproteins composed of two polypeptide chains linked by a disulphide bridge. The A-chain is the enzymatic toxic moiety and B-chain is responsible for bonding to the target cell and internalization of toxin. The toxic part of the toxin molecule removes an adenine from a specific adenosine residue in ribosomal RNA and block proteosynthesis. That is the reason of extreme toxicity of these compounds and their capacity to be used as biological warfare agents or terrorist weapon. Therefore all these compounds are in the schedules of controlled biological agents and toxins. Contrariwise, plant ribosome-inactivating proteins are studied intensive as possible chemotherapeutic agents.