Structure of glycoproteins of human erythrocytes. Alkali-stable oligosaccharides

Abstract

Studies have been made on the oligosaccharide residues of the alkali-stable carbohydrate-protein linkage of sialoglycopeptides derived from human erythrocytes. Four glycopeptides were isolated after alkaline borohydride treatment and Pronase digestion of MN-active sialoglycopeptides. The structure of one of these glycopeptides (GPIV) has been studied by sequential hydrolysis with specific glycosidases. Glycopeptide GPIV contained (per mol): 1mol of fucose, 1mol of sialic acid, 3mol of galactose, 3mol of mannose, 4mol of acetylglucosamine, 1mol of aspartic acid and fractional amounts of threonine, serine and glycine. The molecular weight of the glycopeptide was estimated to be 2330 by gel filtration. On the basis of glycosidase-digestion results, a tentative structure is proposed for the oligosaccharide moiety of glycopeptide GPIV.

Role of galactosyl-transferases in rat gastric epithelial glycoprotein synthesis

“…The oligosaccharides are glycosidically-linked to the polypeptide backbone via GalNAc-serine/threonine bonds. Also other, non-mucin glycoproteins like human chorionic gonadotropin [3], fetuin [4] and the erythrocyte membrane glycoprotein glycophorin [5] contain glycosidic linkages between sugar and amino acid.…”

Characterization of precursor and secreted forms of human angiotensinogen.

“…Our evidence for one precursor synthesized by cell-free translation indicates that only one of the two potential initiation sites is used. In the present study, the difference in apparent molecular weight (3,800) between the precursor (50,000) and the mature nonglycosylated angiotensinogen (46,200) suggests that the signal peptide is 33 rather than 24 amino acids in length, and that the methionine at -33 is the site of initiation of translation. However Glycosylation ofangiotensinogen.…”

“…The failure of these 0-glycosylated forms of angiotensinogen to bind to concanavalin A indicates that they do not contain saccharide residues with affinity for concanavalin A. These data suggest that the 0-linked oligosaccharide units of angiotensinogen may resemble the 0-linked tetrasaccharide units of fetuin, erythrocyte glycophorin and human chorionic gonadotropin (46)(47)(48). These tetrasaccharide units are composed of a serine-linked N-acetylgalactosamine residue attached to a galactose residue, each of which is attached to a sialic acid residue.…”

Changes in expression of a major sialoglycoprotein associated with ascites forms of a mammary adenocarcinoma

“…At least two types of oligosaccharide chains are present. One is a four unit "mucin-like" structure (Thomas and Winzler, 1969), while the other is a larger "plasma" type (Thomas and Winzler, 1971).…”