Isolation and characterization of an avian hepatic binding protein specific for N-acetylglucosamine-terminated glycoproteins

Abstract

An hepatic receptor which recognizes and binds specifically to serum glycoproteins bearing terminal, nonreducing N-acetylglucosamine residues has been purified to homogeneity by affinity chromatography from chicken liver. The isolated binding protein has been characterized as a water-soluble glycoprotein in which sialic acid, galactose, mannose, and glucosamine comprise 8% of the total molecule. The binding reaction is a saturable process and is proportional to receptor concentration. Evidence has been adduced to indicate the presence of a single high affinity binding site with a dissociation constant of 1.4 x 10(-9) M. A single subunit has been identified by polyacrylamide gel electrophoresis in sodium dodecyl sulfate with an estimated molecular weight of 26,000. The chemical and physical properties of the avian protein have been evaluated with respect to the analogous hepatic protein, of mammalian origin, which exhibits a binding specificity for galactose-terminal serum glycoproteins.