Eosinophil Charcot-Leyden crystal protein binds to beta-galactoside sugars

The Charcot-Leyden crystal protein (CLC) found in human eosinophils and basophils has 43-48% amino acid sequence similarity to the galectin family of beta-galactoside binding proteins. We show here that enzymatically active recombinant CLC binds to a lactose-conjugated agarose resin, and that binding is inhibited in a dose dependent fashion by both lactose (IC50 = 41 mM) and fucose (IC50 = 380 mM), but not by arabinose. These results demonstrate that CLC has functional as well as structural homology to the galectins, and suggest that CLC may also participate, as do the galectins, in mediating cell-cell and cell-matrix interactions, and in activating the cellular immune response.