Galactose beta 1-4Fucose (Gal beta 1-4Fuc) is a unique disaccharide exclusively found in N-glycans of protostomia, and is recognized by some galectins of Caenorhabditis elegans and Coprinopsis cinerea. In the present study, we investigated whether mammalian galectins also bind such a disaccharide. We examined sugar-binding ability of human galectin-1 (hGal-1) and found that hGal-1 preferentially binds Gal beta 1-4Fuc compared to Gal beta 1-4GlcNAc, which is its endogenous recognition unit. We also tested other human and mouse galectins, i.e., hGal-3, and -9 and mGal-1, 2, 3, 4, 8, and 9. All of them also showed substantial affinity to Gal beta 1-4Fuc disaccharide. Further, we assessed the inhibitory effect of Gal beta 1-4Fuc, Gal beta 1-4Glc, and Gal on the interaction between hGal-1 and its model ligand glycan, and found that Gal beta 1-4Fuc is the most effective. Although the biological significance of galectin-Gal beta 1-4Fuc interaction is obscure, it might be possible that Gal beta 1-4Fuc disaccharide is recognized as a non-self-glycan antigen. Furthermore, Gal beta 1-4Fuc could be a promising seed compound for the synthesis of novel galectin inhibitors. (C) 2013 Elsevier Inc. All rights reserved.