A lipid-linked oligosaccharide intermediate in glycoprotein synthesis in oviduct. Structural studies on the oligosaccharide chain.
The structure of the oligosaccharide chain of the lipid-linked oligosaccharide that serves as a donor of oligosaccharide chain to proteins of hen oviduct membranes has been investigated. A [Man-14C]glycopeptide fraction was prepared from membrane glycoproteins labeled with GDP-[14C]mannose. Reductive alkaline cleavage of this glycopeptide yielded a reduced oligosaccharide that, by four criteria, was identical with reduced [Man-14C]oligosaccharide prepared from [Man-14C]oligosaccharide-lipid. The structure of the oligosaccharide chain of the [Man-14C]glycopeptide was investigated by cleavage with a specific endo-beta-N-acetylglucosaminidase, followed by treatment of the released oligosaccharide with purified al alpha-and beta-mannosidases. By this procedure it was possible to establish the structure of the cleavage product as (alpha-Man)n-beta-Man-(1 leads to 4)-GlcNAc. Similar studies were performed on the [GlcNAc-14C]oligosaccharide prepared by hydrolysis of [GlcNAc-14C]oligosaccharide-lipid. The results indicate that the structure of the intact oligosaccharide is (alpha-Man)n-beta-Man-(1 leads 4)-beta-GlcNAc-(1 leads to 4)-GlcNAc. These experiments, coupled with earlier enzymatic studies on synthesis of the glycoproteins from the lipid-linked oligosaccharide, provide strong evidence that the structure of the oligosaccharide intermediate and the oligosaccharide chain of the glycoprotein product contain the same core structure found in many secretory glycoproteins.
D000818:Animals; D002645:Chickens; D005260:Female; D006020:Glycopeptides / Q000032:analysis; D006023:Glycoproteins / Q000096:biosynthesis; D006596:Hexosaminidases; D008070:Lipopolysaccharides / Q000378:metabolism; D008361:Mannosidases; D009844:Oligosaccharides / Q000378:metabolism; D010057:Oviducts / Q000032:analysis* / Q000378:metabolism
D006020:Glycopeptides; D006023:Glycoproteins; D008070:Lipopolysaccharides; D009844:Oligosaccharides; D006596:Hexosaminidases; D008361:Mannosidases