title: Novel carbohydrate specificity of the 16-kDa galectin from Caenorhabditis elegans: binding to blood group precursor oligosaccharides (type 1, type 2, Talpha, and Tbeta) and gangliosides.
abstract: Galectins, a family of soluble beta-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, Galbeta1,3GlcNAc, and type 2, Galbeta1,4GlcNAc; Talpha, Galbeta1,3GalNAcalpha; Tbeta, Galbeta1,3GalNAcbeta) and gangliosides containing the Tbeta structure. Homology modeling of the C. elegans 16-kDa galectin CRD revealed that a shorter loop containing residues 66-69, which enables interactions of Glu(67) with both axial and equatorial -OH at C-3 of GlcNAc (in Galbeta1,4GlcNAc) or at C-4 of GalNAc (in Galbeta1,3GalNAc), provides the structural basis for this novel carbohydrate specificity.
authors.affiliation: Center of Marine Biotechnology, University of Maryland Biotechnology Institute, 701 East Pratt Street, Baltimore, MD 21202, USA.
authors.forename: Hafiz
authors.initials: H
authors.lastname: Ahmed
authors.forename: Mario A
authors.initials: MA
authors.lastname: Bianchet
authors.forename: L Mario
authors.initials: LM
authors.lastname: Amzel
authors.forename: Jun
authors.initials: J
authors.lastname: Hirabayashi
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Kasai
authors.forename: Yuko
authors.initials: Y
authors.lastname: Giga-Hama
authors.forename: Hideki
authors.initials: H
authors.lastname: Tohda
authors.forename: Gerardo R
authors.initials: GR
authors.lastname: Vasta
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000943:Antigens, Differentiation / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D017173:Caenorhabditis elegans / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000378:metabolism*; D002240:Carbohydrate Sequence; D037161:Galectins / Q000737:chemistry / Q000378:metabolism*; D005732:Gangliosides / Q000378:metabolism*; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism; D008024:Ligands; D008958:Models, Molecular; D008970:Molecular Weight; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012568:Schizosaccharomyces / Q000235:genetics; D016415:Sequence Alignment; D040681:Structural Homology, Protein; D013329:Structure-Activity Relationship
chemical_list: D000943:Antigens, Differentiation; D029742:Caenorhabditis elegans Proteins; D037161:Galectins; D005732:Gangliosides; D006023:Glycoproteins; D008024:Ligands; D009844:Oligosaccharides; D011994:Recombinant Proteins