Ricinus communis agglutinin II (RCA II, RCA60, ricin)

Ricinus communis agglutinin II is an extremely toxic glycoprotein consisting of two disulfide-linked chains of about 28,000 daltons and 32,000 daltons, termed A and B chain, respectively. The B chain can bind to cell surfaces via galactose or N-acetylgalactosamine residues of membrane glycoconjugates and facilitates the transport of the lectin into the cell. The A chain has an enzyme activity which can catalytically block protein synthesis and is so toxic that only a single molecule of A chain is required to kill a cell. Alone, the A chain is incapable of entering the cell and is thus not toxic. The A chain can be separated from the B chain and then linked by a cleavable disulfide bond to other proteins, such as antibodies. These antibody-toxin hybrid molecules can be used to kill specific cells with the appropriate antigenic determinant exposed, such as tumor markers on surfaces of malignant cells. 
RCA60 appears to be a family of related lectins with different toxicities. Our RCA60 is the most toxic lectin of this family, probably ricin D, having an I.P. L.D50 in 20 g mice of less than 50 ng. 
Inhibiting/Eluting Sugar: 200 mM galactose or lactose