Structure of S-lectin, a developmentally regulated vertebrate beta-galactoside-binding protein

An unexpected structural link to legume lectins, notwithstanding the absence of sequence homology, is evident in the crystal structure of a 14-kDa bovine spleen S-lectin complexed with the disaccharide N-acetyllactosamine at a resolution of 1.9 angstroms. An extended beta-sandwich results from the association of a pair of monomers. Complex interactions that limit the position of the O4 atom are responsible for the specificity of beta-galactose.