TENDON EXTRACELLULAR-MATRIX CONTAINS PENTAMERIC THROMBOSPONDIN-4 (TSP-4)

In preparations of cartilage oligomeric matrix protein (COMP) from bovine tendon two contaminating polypeptides of 120 and 135 kDa were detected, N-Terminal protein sequencing of these polypeptides showed homology to the N-terminus and to an internal sequence in TSP-4, respectively, TSP-4 was further enriched by heparin affinity chromatography, Electron microscopy of this sample shows primarily five armed particles with globular domains at the periphery connected to a central assembly domain in,which smaller N-terminal globular domains can be resolved tightly packed at the center of the particle, We can thereby confirm the pentameric model for TSP-4 proposed by Lawler et al, [(1995) J. Biol. Chem, 270, 2809-2814], on the basis of recombinantly expressed protein, We further show that TSP-4 is abundant in tendon.