The 30 kDa β-galactoside-binding protein of baby hamster kidney (BHK) cells [Mehul et al. (1994), J. Biol. Chem. 269, 18250–18258] homologous to galectin 3, a widely distributed mammlian lectin, has been found to be a substrate for tissue type transglutaminase, as shown by the incorporation in a calcium- and time-dependent manner of 5-(biotinamido) pentylamine in the presence of guinea pig liver transglutaminase. The amino-terminal domain of hamster galectin 3, which is a repetitive sequence rich in glutamine, tyrosine, glycine and proline, is also an excellent substrate. A single lysine residue in the N-terminal domain is an essential requirement for transglutaminase-mediated oligomerization, and two equivalent glutamine residues present in identical sequence repeats within dhis domain appear to be involved as amine acceptors in cross-linking reactions. Transglutaminase-mediated cross-linking of galectin 3 to itself or to matrix components may be one mechanism for stablisation of a multivalent binding form of the lectin in cell secretions or in extracellular matrices.
