Matrilin-3 forms disulfide-linked oligomers with matrilin-1 in bovine epiphyseal cartilage

A comparison of noncollagenous matrix proteins from different types of bovine cartilage by SDS-polyacrylamide gel electrophoresis showed a prominent 240-kDa component in extracts of epiphyseal but not tracheal tissue. On amino-terminal sequence analysis, it gave two sequences. One matched the NH2 terminus of cartilage matrix protein (CMP) as reported for tracheal cartilage. The other did not match any known protein sequence. Further analysis of the 240-kDa protein after reduction of disulfides resolved two bands on SDS-polyacrylamide gel electrophoresis. Isolation and sequence analysis of tryptic peptides confirmed that one was bovine CMP and the other a CMP homolog. A data base search identified the latter as matrilin-3, a molecule recently predicted from human and mouse cDNA sequences (Wagener, R., Kobbe, B., and Paulsson, M. (1997) FEBS Lett. 413, 129-134). Matrilin-3 and CMP (matrilin-1) were prominent in equimolar amounts in fetal bovine epiphyseal cartilage and absent from adult articular cartilage. Adult tracheal cartilage contained almost exclusively CMP. Although the mechanism of polymeric assembly is unknown, the matrilin-3 chain appears to function in the matrix linked to matrilin-1 in the form of disulfide-bonded heteromeric molecules. The results indicate a molecular stoichiometry of (matrilin-1)2(matrilin-3)2.