Glycobiology, 2002, Vol. 12, No. 8 451-461
© 2002 Oxford University Press
Novel carbohydrate specificity of the 16-kDa galectin from Caenorhabditis elegans: binding to blood group precursor oligosaccharides (type 1, type 2, T
, and Tß) and gangliosides
2 Center of Marine Biotechnology, University of Maryland Biotechnology Institute, 701 East Pratt Street, Baltimore, MD 21202, USA; 3 Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA; 4 Department of Biological Chemistry, Faculty of Pharmaceutical Sciences, Teikyo University, Sagamiko, Kanagawa 199-01, Japan; and 5 Research Center, Asahi Glass Co. Ltd., Yokohama-shi, Kanagawa 221, Japan
Galectins, a family of soluble ß-galactosyl-binding lectins, are believed to mediate cell–cell and cell–extracellular matrix interactions during development, inflammation, apoptosis, and tumor metastasis. However, neither the detailed mechanisms of their function(s) nor the identities of their natural ligands have been unequivocally elucidated. Of the several galectins present in the nematode Caenorhabditis elegans, the 16-kDa "proto" type and the 32-kDa "tandem-repeat" type are the best characterized so far, but their carbohydrate specificities have not been examined in detail. Here, we report the carbohydrate-binding specificity of the recombinant C. elegans 16-kDa galectin and the structural analysis of its binding site by homology modeling. Our results indicate that unlike the galectins characterized so far, the C. elegans 16-kDa galectin interacts with most blood group precursor oligosaccharides (type 1, Galß1,3GlcNAc, and type 2, Galß1,4GlcNAc; T
, Galß1,3GalNAc; Tß, Galß1,3GalNAcß) and gangliosides containing the Tß structure. Homology modeling of the C. elegans 16-kDa galectin CRD revealed that a shorter loop containing residues 66–69, which enables interactions of Glu67 with both axial and equatorial -OH at C-3 of GlcNAc (in Galß1,4GlcNAc) or at C-4 of GalNAc (in Galß1,3GalNAc), provides the structural basis for this novel carbohydrate specificity.
1 To whom correspondence should be addressed; E-mail: vasta@umbi.amd.edu
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