CHITIN-BINDING PROTEINS FROM COWPEA (VIGNA-UNGUICULATA) SEEDS

Vicilins (7S storage proteins) from cowpea (Vigna unguiculata) and oth er legume seeds were shown to bind to chitin, to regenerated chitin (f ully acetylated chitin) and to chitosan (deacetylated chitin). Adsorbe d vicilins were desorbed from these matrices by acetic and hydrochlori c acids and by highly polymerized soluble chitosan. Proteins such as t he lectin of common bean (PHA), soybean trypsin inhibitor (Kunitz), a beta-1,3-glucanase from cowpea seeds, bovine pancreatic alpha-chymotry psin, chicken ovalbumin, serum albumin and rabbit gamma-globulin did n ot bind. The present result is the first description of vicilin bindin g to chitin but other proteins, such as wheat germ agglutinin (WGA), a lectin that contains the so called ''chitin-binding domain'', and a c hitinase isolated from cowpea seeds, which are involved in the defense mechanisms of plants against insects and fungi, were also shown to bi nd to chitin as previously reported. The binding of vicilins to chitin is probably effected not through a ''chitin-binding domain'' because they do not share this sequence with the defense-related proteins cite d above. We propose that this association of vicilins with chitin may be related to the effect of variant vicilins on the development of Cal losobruchus maculatus (bruchid) in resistant cowpea seeds.