Terminal alpha-linked galactose rather than N-acetyl lactosamine is ligand for bovine heart galectin-1 in N-linked oligosaccharides of glycoproteins.
Preference for the beta-anomer of galactose attributed to the bovine heart 14 kDa galectin-1 (BHL-14) was re-examined using natural glycoproteins and artificially glycosylated proteins as ligands. Endogenous glycoproteins co-purified with BHL-14 during its affinity chromatographic isolation contained oligosaccharides bearing terminal alpha-linked galactose (TAG) moieties and were superior even to laminin as ligands for homogeneous BHL-14 obtained by high pressure liquid chromatography. Artificially glycosylated proteins prepared by covalent attachment of melibiose to proteins and containing TAG moieties were ligands for BHL-14, unlike their lactose counterparts which contained beta-linked galactose. Enzymatic removal of TAG moieties from the following glycoproteins abolished their recognition by BHL-14: (i) endogenous glycoproteins co-purified with BHL-14; (ii) mouse laminin; and (iii) bovine heart glycoproteins recognized by peanut agglutinin. Modification of TAG in laminin using galactose oxidase also rendered the glycoprotein inert towards BHL-14. Desialylation of human IgG, bovine thyroglobulin or laminin failed to increase the affinity of BHL-14 for these glycoproteins. Since removal of TAG or of sialic acid moiety exposed LacNAc (Gal beta1-->4 GlcNAc) in these glycoproteins, these results indicated that TAG, rather than LacNAc, is a ligand for BHL-14 on N-linked oligosaccharide chains of glycoproteins. Ready recognition of human IgA and jacalin-binding human plasma glycoproteins and non-recognition of human IgG suggested that T antigen (Galbeta1-->3 GalNAc) may also be ligand for galectin-1.
Appukuttan
P S
PS
Division of Biochemistry, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram-695011, India. psappu@sctimst.Ker.nic.in
D000606:Amino Sugars / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D002417:Cattle; D002846:Chromatography, Affinity / Q000379:methods; D002851:Chromatography, High Pressure Liquid; D005690:Galactose / Q000737:chemistry / Q000378:metabolism*; D037483:Galectin 1 / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D006321:Heart; D006801:Humans; D008024:Ligands; D009844:Oligosaccharides / Q000032:analysis / Q000138:chemical synthesis / Q000737:chemistry; D011485:Protein Binding
D000606:Amino Sugars; D037483:Galectin 1; D006023:Glycoproteins; D008024:Ligands; D009844:Oligosaccharides; C000458:N-acetyllactosamine; D005690:Galactose