Structure and evolution of ricin B chain

Nature. 1987 Apr 9-15;326(6113):624-6. doi: 10.1038/326624a0.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Biological Evolution
  • Galactose / metabolism
  • Multigene Family
  • Protein Conformation
  • Ricin* / genetics


  • Ricin
  • Galactose