title: Monoglucosylated glycans in the secreted human complement component C3: implications for protein biosynthesis and structure.
abstract: The monoglucosylated oligomannose N-linked oligosaccharide (Glc(1)Man(9)GlcNAc(2)) is a retention signal for the calnexin-calreticulin quality control pathway in the endoplasmic reticulum. We report here the presence of such monoglucosylated N-glycans on the human complement serum glycoprotein C3. This finding represents the first report of monoglucosylated glycans on a human serum glycoprotein from non-diseased individuals. The presence of the glucose moiety in 5% of the human C3 glycoprotein suggests that this glycosylation site is sequestered within the protein and is consistent with previous studies identifying a cryptic conglutinin binding site on C3 that becomes exposed upon its conversion to iC3b.
authors.affiliation: Department of Biochemistry, Oxford Glycobiology Institute, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
authors.forename: M D Max
authors.initials: MD
authors.lastname: Crispin
authors.forename: Gayle E
authors.initials: GE
authors.lastname: Ritchie
authors.forename: Alison J
authors.initials: AJ
authors.lastname: Critchley
authors.forename: B Paul
authors.initials: BP
authors.lastname: Morgan
authors.forename: Ian A
authors.initials: IA
authors.lastname: Wilson
authors.forename: Raymond A
authors.initials: RA
authors.lastname: Dwek
authors.forename: Robert B
authors.initials: RB
authors.lastname: Sim
authors.forename: Pauline M
authors.initials: PM
authors.lastname: Rudd
mesh_terms: D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003176:Complement C3 / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D006023:Glycoproteins / Q000096:biosynthesis* / Q000737:chemistry; D006026:Glycoside Hydrolases / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D008351:Mannans / Q000737:chemistry; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism*
chemical_list: D003176:Complement C3; C092383:Glc(1)Man(9)GlcNAc(2) oligosaccharide; D006023:Glycoproteins; D008351:Mannans; D009844:Oligosaccharides; D011134:Polysaccharides; C475461:mannosyl(9)-N-acetylglucosamine2; D006026:Glycoside Hydrolases