Cross-linking activities of galectins and other multivalent lectins

The multivalent binding activities of lectins including certain galectins lead to the formation of type-1 and type-2 cross-linked complexes with multivalent carbohydrates and glycoconjugates. Type-1 complexes occur between divalent lectins and divalent carbohydrates or glycoconjugates which yield 1-dimensional cross-linked complexes. This type of complex has been observed between galectin-1 from bovine heart muscle and a bivalent N-linked biantennary complex glycopeptide (Bourne et al., 1994). Type-2 interactions occur between lectins and carbohydrates or glycoconjugates where one of the two molecules possesses a valency greater than two. In this case, 2- and 3-dimensional cross-linking occurs which may be homogeneous if crystal packing interactions are present. Evidence indicates that calf spleen galectin-1 undergo type-2 cross-linking interactions with ASF (Gupta and Brewer, 1994). The flexibility of certain galectins such as galectin-1 to form type-1 and type-2 cross-linked complexes with carbohydrates and glycoconjugates may relate to the biological activities of this animal lectin, and to the activities of other members of the galectin family.