Cartilage oligomeric matrix protein shows high affinity zinc-dependent interaction with triple helical collagen.
Cartilage and tendon extracellular matrices are composed of collagens, proteoglycans, and a number of noncollagenous proteins. Cartilage oligomeric matrix protein (COMP) is a prominent such protein, structurally related to the thrombospondins. We found that native COMP binds to collagen I/II and procollagen I/II and that the interaction is dependent on the divalent cations Zn2+ or Ni2+, whereas Ca2+, Mg2+, and Mn2+ did not promote binding. Using a solid phase assay, Scatchard analysis identified one class of binding site with a dissociation constant (Kd) close to 1.5 nM in the presence of Zn2+. The results were confirmed by studies using surface plasmon resonance. Furthermore, metal chelate chromatography demonstrated that COMP bound Zn2+ and Ni2+. Electron microscopy showed that the interaction occurred at four defined sites on the 300-nm collagen and procollagen molecules. Two were located close to each end, and two at 126 and 206 nm, respectively, from the C-terminal. COMP interacted via its C-terminal globular domain and significantly only in the presence of Zn2+.
Department of Cell and Molecular Biology, Section of Connective Tissue Biology, Lund University, S-221 00 Lund, Sweden.
K
K
Rosenberg
H
H
Olsson
M
M
Mörgelin
D
D
Heinegård
D001665:Binding Sites / Q000502:physiology; D015374:Biosensing Techniques; D002356:Cartilage / Q000378:metabolism*; D003094:Collagen / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism*; D007700:Kinetics; D064235:Matrilin Proteins; D008854:Microscopy, Electron; D009532:Nickel / Q000378:metabolism; D011347:Procollagen / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D015032:Zinc / Q000378:metabolism*
D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; D064235:Matrilin Proteins; D011347:Procollagen; D009532:Nickel; D003094:Collagen; D015032:Zinc