Glycoprotein lectins isolated from seeds of the castor bean Ricinus communis. Agglutinin I (RCA-I, 564 aa) has binding specificity similar to ricin, but is much less toxic. It binds preferentially to oligosaccharides ending in galactose, but may also interact with N-acetylgalactosamine. Agglutinin-II (ricin) is an AB toxin; the A subunit (267 aa) enzymically inactivates ribosomes (at a rate of a few thousand per minute, faster than they can be replaced), and is disulphide-linked to the carbohydrate-binding B subunit (262 aa) that binds β-galactosyl residues.
Subjects: Medicine and Health.