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.
Laboratoire de Biochimie, Faculté de Pharmacie, Université de Lille II, Avenue du Professeur Laguesse, B.P. 83, F-59006 Lille, France.
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Flahaut
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Capon
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Balduyck
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Ricart
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Sautiere
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Mizon
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