was found to possess an unusually high carbohydrate content (76%) comprised of NeuAc, Gal, Man, Fuc, GalNAc, and GlcNAc.The aim of the present investigation was to elucidate the primary structure of the oligosaccharide units of this protein.For the study of the 0-glycosidic oligosaccharide chains, the protein was subjected to @-elimination and the resulting oligosaccharide preparations were analyzed by 500-MHz 'H NMR spectroscopy.The structure of the predominant glycan, a hexasaccharide:NeuAca(24)G@( 14)GlcNAc@( 1+6) and that of a tetrasaccharide: NeuAca(2-3)Gal@( 1 4 3)[NeuAca(2~6)]GalNA~-ol, were determined.The protein possesses approximately 40 hexasaccharides and 3 tetrasaccharides/mol.For the isolation of its N-glycosidic oligosaccharide chains, the protein was exhaustively digested with proteases followed by chromatography of the desialyzed resulting glycopeptide fraction on concanavalin A- Sepharose.600-MHz 'H NMR spectroscopy of the obtained preparations revealed the presence of 3 diantennary N-glycosidic chains that are extended with a Fuc residue at the Asn-linked GlcNAc.
The amino acid sequence of galactoglycoprotein purified from human plasma was elucidated to 75% completeness by using chemical degradation of peptides and glycopeptides derived from digests of the protein with seven specific proteases. This sequence represents a polypeptide chain of approximately 220 amino acid residues including a high content of serine, threonine, alanine, and proline with one N-linked and multiple O-linked glycans. Comparison of peptide sequences from the native galactoglycoprotein and the deglycosylated derivative demonstrated the locations of 25 sites of O-glycosylation and three serine sites that are not glycosylated. The homogeneous N terminus was established as serine. C-terminal analysis revealed multiple C-terminal residues, suggesting that galactoglycoprotein molecules are of varying lengths. A search of a protein data base revealed that the galactoglycoprotein polypeptide is identical to the N-terminal (extracellular) polypeptide region of the blood-cell surface molecule CD43 (sialophorin, leukosialin). Further support of the relatedness of these molecules was obtained by immunoprecipitation of 125I-labeled galactoglycoprotein by monoclonal anti-CD43 antibodies. The composition and properties of the molecules together with the known structure of the gene encoding CD43 suggest that galactoprotein is derived by proteolytic cleavage from transmembrane "hexasaccharide CD43," known to be expressed on neutrophils, activated T lymphocytes, and platelets.
The beta2-microglobulin from human colostrum was purified by a combination of ordinary protein-chemical techniques: gel filtration, ion-exchange chromatography and zone electrophoresis. The procedure is organized in such a way that the simultaneous isolation of many other milk proteins is possible. The beta2-microglobulin obtained from colostrum cannot be distinguished by physical-chemical or immunological means from the beta2-microblobulin isolated from the urine of patients with kidney-tubule diseases. At the beginning of lactation, human milk contains significantly more than 10 mg/-100 ml beta2-microglobulin, but the concentration drops within two or three days to 15-30% of the original amount.
Human serum glycoproteins can be classified into those containing N-acetyl-D-galactosamine and into those lacking this hexosamine.The N-acetyl-D-galactosamine-containing serum glycoproteins have alkali-labile chains containing this hexosamine linked 0-glycosidically to hydroxy amino acids.These alkali-labile chains can be demonstrated in neuraminic acid free serum glycoproteins by gas liquid chromatography and by using precipitating lectins from invertebrates and plants.They are represented by two chains, one containing only N-acetyl-D-galactosamine, the other with Z)-galactose linked (1-3) j3-glycosidically to this hexosamine forming a disaccharide.Scrologically these two chains, which usually occur together on one molecule, can be characterized by their reaction with lectins from Helix pomatia (anti-A like) and from Agaricus bisporus andArachis hypogaea (anti-TF specificity). Immunchemische Untersuchungen an alkali-labilen Kohlenhydratketten menschlicher Serum-Glykoproteine
