Abrin properties

Funatsu, G., Funatsu, M. (1970). Isolation and chemical properties of various types of ricin. Jpn. J. Med. Sci. Biol. 23 342-4 Gareth, D., Griffiths, G.D., Rice, P., Allenby, A.C., Bailey, S.C., Upshall, D.G. (1995). Inhalation toxicology and histopa-thology of ricin and abrin toxins. Inhal. Toxicol. 7 269-88 Gill, D.M. (1982). Bacterial toxins a table of lethal amounts. Microbiol. Rev. 46 86-94. 

Olsnes, S. and Pihl, A. (1973h) Isolation and properties of abrin a toxic protein inhibiting protein synthesis. Evidence for different biological functions of its two constituent-peptide chains. Eur J Biochem, 35, 179-185. 

Olsnes, S., Sandvig, K., Eiklid, K. and Pihl, A. (1978b) Properties and action mechanism of the toxic lectin modeccin interaction with cell fines resistant to modeccin, abrin, and ricin. J Supramol Struct, 9, 15-25. 

Abrin is a plant toxin, which is closely related to ricin in terms of its structure and chemical properties. It is obtained from the seeds of Abrus pre-catorius (commonly known as jequirity bean or rosary pea ), a tropical vine cultivated as an ornamental plant in many locations. Jequirity beans are usually scarlet in colour with a black spot at one end (though less common different coloured varieties exist) and are approximately 3x8 mm in size. 

The structural similarity of abrin to ricin is reflected also in its toxicokinetic properties with... 

Abrin applied to the eye causes severe inflammation of the conjunctiva with localized necrosis (Grant and Schuman, 1993). At the end of the 19th Century, the extract of jequirity bean was used therapeutically for its inflammatory properties, to treat various eye complaints including trachoma. However, the inflammation produced was very difficult to control and, in some cases, the use of this infusion resulted in permanent damage to the cornea, and occasionally blindness (Grant and Schuman, 1993). 

In the late 1800s, Stillmark4 discovered that the beans of the castor plant contained a toxic protein, which he named ricin. He discovered that ricin caused agglutination of erythrocytes and precipitation of serum proteins. (The lectin properties of ricin and abrin [a closely related toxin from the bean of Abrus precatorius] and their use as tools for research were described in 1972 by Sharon and Lis.5)... 

The brilliant red black seeds oiAbrus precatorius (precatory bean) contain abrin, an extremely toxic protein (Ghosal and Dutta, 1971). Seeds of this plant are commonly used in the tropics to make necklaces and other jewelry. One seed, if thoroughly masticated, is sufficient to cause death in a child (Kingsbury, 1964). The lectins of this plant primarily bind galactose and are similar in properties to those of ricin (see below). The lectin has a molecular weight of 65,000 and is composed of dissimilar peptides. 

Ricin a toxalbumin phytotoxin from Ricinus seeds. M, 66,000,493 amino acid residues. R. inhibits protein biosynthesis (causes dissociation of polysomes) and has antitumor properties. It consists of an A-chain (M, 32,000) and a B-chain (M, 34,000) joined by disulfide bridges. After reductive separation by 2-mercap-toethanol, both chains show increased inhibitor activity but markedly decreased toxicity. Toxic activity is carried by the A-chain (effectomer), while the B-chain (haptomer) binds the toxin to the cell surface. Similar action and structure are possessed by abrin (M, 65,000 A-chain 30,000, B-chain 35,000), a toxalbumin from the red seeds of Abrus precatorius. Abrin is used in opthalmology. 

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