The Jequirity, also called Black-eyed Susan, Rosary Pea or Indian Licorice (Abrus precatorius), is a legume with long, pinnate-leafleted leaves. Their seeds are often used as beads and in percussion instruments. The seed is highly poisonous but is unlikely to harm if swallowed raw and unbroken, as they have a hard seed coat.
The toxin present in abrus precatorius is a close relative to ricin called abrin. It is a dimer consisting of two protein subunits, termed A and B. The B chain is abrin's "ticket" into the cell: it bonds to certain transport proteins on cell membranes, which then transport the toxin into the cell. Once inside the cell, the A prevents protein synthesis by inactivating the 26S subunit of the ribosome. One molecule of abrin will inactivate up to 1,500 ribosomes per second. Symptoms are identical to those of ricin, except that the fatal dose of ricin is approximately 75 times greater than the fatal dose of abrin. Abrin can kill with a circulating amount of less than 3 μg (micrograms).
The seeds of abrus precatorius are much valued in native jewelry for their bright coloration. The third of the bean with the hilum (attachment scar) is black, while the rest is bright red, suggesting a ladybug. Jewelry-making with jequirity seeds is dangerous, and there have been cases of death by a finger-prick while boring the seeds for beadwork.
Seeds of Abrus precatorius contain two distinct but structurally related Type 2 RIPs. Abrin is an extremely potent toxin but a weak agglutinin, whereas APA is a potent erythroagglutinin with relatively low cytotoxicity. For characterizations of APA-I and APA-II see: Anal Biochem 1991 Apr;194(1):101-9) Abrin has anti-carcenogenic activity. See: Cancer Research 1982 (42)276-27
Compared with the Abrus lectin, which strongly agglutinates rabbit erythrocytes and human A,B and O erythrocytes, abrin shows only weak aggltuinating activity. See:Eur. J. Biochem 1973 (35)179-185 ABA is a potent mitogen to thymus derived lymphocytes. See: Meth. Enzymol. 1978 (50)323-330