title: Structure and evolution of ricin B chain.
abstract: Ricin is a dimeric toxin from the castor bean Ricinus communis, which is composed of a sugar-binding subunit (B) that attaches to receptors on the surfaces of target cells and a subunit (A) with enzymatic activity that attacks and inactivates ribosomes. We report here that comparison of amino-acid sequence data with high-resolution structure analysis of the ricin B subunit shows it to be the product of a series of gene duplications. The modern protein has two sugar-binding domains, each of which is composed of three copies of a more ancient galactose-binding peptide of about 40 residues.
mesh_terms: D000595:Amino Acid Sequence; D005075:Biological Evolution; D005690:Galactose / Q000378:metabolism; D005810:Multigene Family; D011487:Protein Conformation; D012276:Ricin / Q000235:genetics
chemical_list: D012276:Ricin; D005690:Galactose