title: Characterization of recombinant amino-terminal NC4 domain of human collagen IX: interaction with glycosaminoglycans and cartilage oligomeric matrix protein.
abstract: The N-terminal NC4 domain of collagen IX is a globular structure projecting away from the surface of the cartilage collagen fibril. Several interactions have been suggested for this domain, reflecting its location and its characteristic high isoelectric point. In an attempt to characterize the NC4 domain in more detail, we set up a prokaryotic expression system to produce the domain. The purified 27.5-kDa product was analyzed for its glycosaminoglycan-binding potential by surface plasmon resonance and solid-state assays. The results show that the NC4 domain of collagen IX specifically binds heparin with a K(d) of 0.6 microm, and the full-length recombinant collagen IX has an even stronger interaction with heparin, with an apparent K(d) of 3.6 nm. The heparin-binding site of the NC4 domain was located in the extreme N terminus, containing a heparin-binding consensus sequence, whereas electron microscopy suggested the presence of at least three additional heparin-binding sites on full-length collagen IX. The NC4 domain was also shown to bind cartilage oligomeric matrix protein. This interaction and the association of cartilage oligomeric matrix protein with other regions of collagen IX were found to be heparin-competitive. Circular dichroism analyses of the NC4 domain indicated the presence of stabilizing disulfide bonds and a thermal denaturation point of about 80 degrees C. The pattern of disulfide bond formation within the NC4 domain was identified by tryptic peptide mass mapping of the NC4 in native and reduced states. A similar pattern was demonstrated for the NC4 domain of full-length recombinant collagen IX.
authors.affiliation: NMR Laboratory, Institute of Biotechnology, University of Helsinki, Finland. Tero.Pihlajamaa@helsinki.fi
authors.forename: Tero
authors.initials: T
authors.lastname: Pihlajamaa
authors.forename: Hilkka
authors.initials: H
authors.lastname: Lankinen
authors.forename: Joni
authors.initials: J
authors.lastname: Ylöstalo
authors.forename: Leena
authors.initials: L
authors.lastname: Valmu
authors.forename: Juha
authors.initials: J
authors.lastname: Jäälinoja
authors.forename: Frank
authors.initials: F
authors.lastname: Zaucke
authors.forename: Luitgard
authors.initials: L
authors.lastname: Spitznagel
authors.forename: Silke
authors.initials: S
authors.lastname: Gösling
authors.forename: Anne
authors.initials: A
authors.lastname: Puustinen
authors.forename: Matthias
authors.initials: M
authors.lastname: Mörgelin
authors.forename: Johan
authors.initials: J
authors.lastname: Peränen
authors.forename: Patrik
authors.initials: P
authors.lastname: Maurer
authors.forename: Leena
authors.initials: L
authors.lastname: Ala-Kokko
authors.forename: Ilkka
authors.initials: I
authors.lastname: Kilpelaïnen
mesh_terms: D001665:Binding Sites; D019921:Biotinylation; D002356:Cartilage / Q000378:metabolism*; D002942:Circular Dichroism; D003094:Collagen / Q000737:chemistry; D024081:Collagen Type IX / Q000737:chemistry*; D004220:Disulfides; D006025:Glycosaminoglycans / Q000737:chemistry*; D006493:Heparin / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D013058:Mass Spectrometry; D008854:Microscopy, Electron; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D020349:Surface Plasmon Resonance; D013696:Temperature; D013997:Time Factors
chemical_list: D024081:Collagen Type IX; D004220:Disulfides; D006025:Glycosaminoglycans; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D006493:Heparin; D003094:Collagen