Study of the glycosylation of apolipoprotein H.
Apolipoprotein H is a single chain polypeptide composed of 326 amino acids highly glycosylated. Its carbohydrate content is approximately 19% of the molecular weight. We show that it is rich in sialic acid linked alpha (2-6) to galactose or N-acetylgalactosamine. Sialic acid is not alpha (2-3) linked to galactose. Galactose is beta (1-4) linked to N-acetylglucosamine and beta (1-3) linked to N-acetylgalactosamine. Carbohydrate O-linked chains (mainly sialic acid) are alpha (2-6) linked to galactose or N-acetylgalactosamine. Galactose is also organised in O-linked chains and beta (1-4) linked to N-acetylglucosamine and beta (1-3) linked to acetylgalactosamine. Concanavalin A lectin was used to isolate two groups of apolipoprotein H molecules bearing biantennary and truncated hybrids and high mannose and hybrid oligosaccharides. Apolipoprotein H fails to bind lysine-Sepharose. Our results thus show that it presents truncated hybrid or hybrid-type carbohydrate chains which bear few unmasked mannose residues as a terminal sugar. Biochemical analysis of carbohydrate structures conducted on single isoforms separated through IEF revealed that no specific carbohydrate complex is bound to a single isoform.
Gambino
R
R
Dipartimento di Medicina Interna, Universitá di Torino, Turin, Italy.
Ruiu
G
G
Pagano
G
G
Cassader
M
M
D002846:Chromatography, Affinity; D004187:Disaccharides / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D006023:Glycoproteins / Q000097:blood* / Q000737:chemistry* / Q000302:isolation & purification; D006031:Glycosylation; D006801:Humans; D009844:Oligosaccharides / Q000737:chemistry* / Q000302:isolation & purification; D020033:Protein Isoforms / Q000097:blood / Q000737:chemistry / Q000302:isolation & purification; D053482:beta 2-Glycoprotein I
D004187:Disaccharides; D006023:Glycoproteins; D009844:Oligosaccharides; D020033:Protein Isoforms; D053482:beta 2-Glycoprotein I