Glycosylation pattern of human inter-alpha-inhibitor heavy chains.
Human inter-alpha-inhibitor (IalphaI) is a plasma serine-proteinase inhibitor. It consists of three polypeptide chains covalently linked by a glycosaminoglycan chain: a light chain named bikunin carrying the anti-proteinase activity and two heavy chains, H1 and H2, which exhibit specific properties, e.g. they interact with hyaluronan thus stabilizing the extracellular matrix. In this study, using matrix-assisted laser desorption ionization-time-of-flight MS and amino acid sequencing of tryptic peptides, we provide a detailed analysis of the glycosylation pattern of both heavy chains. H1 carries two complex-type N-glycans of predominantly biantennary structure linked to asparagine residues at positions 256 and 559 respectively. In contrast, the oligosaccharides attached to H2 are a complex-type N-glycan in the N-terminal region of the protein (Asn64) and three to four type-1 core-structure O-glycans mono- or di-sialylated, clustered in the C-terminal region. We propose that these O-glycans might function as a recognition signal for the H2 heavy chain. The biological implications of this hypothesis, notably for the biosynthetic pathway of IalphaI, are discussed.
Flahaut
C
C
Laboratoire de Biochimie, Faculté de Pharmacie, Université de Lille II, Avenue du Professeur Laguesse, B.P. 83, F-59006 Lille, France.
Capon
C
C
Balduyck
M
M
Ricart
G
G
Sautiere
P
P
Mizon
J
J
D000510:Alpha-Globulins / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid; D006020:Glycopeptides / Q000737:chemistry / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D015842:Serine Proteinase Inhibitors / Q000737:chemistry / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D000510:Alpha-Globulins; D006020:Glycopeptides; D046911:Macromolecular Substances; D015842:Serine Proteinase Inhibitors; C011877:inter-alpha-inhibitor