PMID: 7682553

 

    Legend: Sugar

Title : Presence of the protein-glycosaminoglycan-protein covalent cross-link in the inter-alpha-inhibitor-related proteinase inhibitor heavy chain 2/ bikunin

Abstract :

1. HC2 / bikunin is a human plasma proteinase inhibitor composed of two polypeptide chains that resist dissociation under reducing conditions in SDS-polyacrylamide gel electrophoresis
2. This observation suggests that a nondisulfide cross-link is responsible for the association of these two polypeptide chains
3. In this study, we have utilized a variety of techniques to investigate the structural basis for this observation
4. We show that the cross-link between the two protein chains is sensitive to chondroitin sulfate-degrading enzymes and to 50 mM NaOH, properties shared by the protein-glycosaminoglycan-protein cross-link found in the related pre-alpha-inhibitor (Enghild, J. J., Salvesen, G., Hefta, S., Thøgersen, I. B., Rutherfurd, S., and Pizzo, S. V. (1991) J. Biol
5. Chem
6. 266, 747-751)
7. Biochemical and mass spectrometric analysis of the peptides containing the cross-link indicate that it is mediated by a chondroitin-4-sulfate chain that originates from a typical O-glycosidic link to Ser10 of bikunin
8. The COOH-terminal Asp648 residue of heavy chain 2 is esterified via the alpha-carbon to C-6 of an internal N-acetylgalactosamine of the chondroitin-4-sulfate chain
9. This suggests that the protein-glycosaminoglycan-protein cross-link that assembles the chains of pre-alpha-inhibitor is identical to that which assembles HC2 / bikunin , and is probably a characteristic of the bikunin proteins