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,...

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Bibliographic Details
Published in:Biochemical journal 1998-08, Vol.333 ( Pt 3) (3), p.749-756
Main Authors: Flahaut, C, Capon, C, Balduyck, M, Ricart, G, Sautiere, P, Mizon, J
Format: Article
Language:English
Subjects:
Alpha-Globulins - chemistry
Alpha-Globulins - metabolism
Amino Acid Sequence
Carbohydrate Sequence
Chromatography, High Pressure Liquid
Glycopeptides - chemistry
Glycopeptides - metabolism
Glycosylation
Humans
Macromolecular Substances
Molecular Sequence Data
Serine Proteinase Inhibitors - chemistry
Serine Proteinase Inhibitors - metabolism
Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
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Summary: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.
ISSN:0264-6021
1470-8728
DOI:10.1042/bj3330749