Characterization of a Large Chondroitin Sulfate Proteoglycan Present in Bovine Collateral Ligament

Bovine collateral ligament synthesized a35S-labeled large proteoglycan species which eluted with aKavof ∼0.27 on Sepharose CL-2B and contained only chondroitin sulfate chains with a molecular mass of ∼32 kDa. Fluorography of the35S-labeled core proteins derived from the large ligament proteoglycan revealed a broad range of molecular masses above ∼200 kDa, which was of comparable size to the four major endogenous core protein bands derived from this proteoglycan detected with 5/6/3-B-3, an antibody directed against terminal unsaturated chondroitin-6-sulfate disaccharides. The core proteins derived from the large ligament proteoglycan exhibited immunoreactivity to 12/21/1-C-6, an antibody specific for a peptide epitope common to both the G1 and G2 domains of aggrecan. Four major core protein bands with molecular masses greater than ∼200 kDa derived from the large ligament proteoglycan, were detected using the antibodies raised against versican from bovine aorta or human fibroblasts. Compared with aggrecan, the35S-labeled large ligament proteoglycan was distributed over a broader range of buoyant densities in an associative caesium chloride density gradient. This polydispersity may be indicative of differences in the degree of glycosylation as well as heterogeneity in the size of the large ligament proteoglycan core proteins. The35S-labeled large ligament proteoglycan also demonstrated the ability to form complexes with an aggrecan aggregate preparation, the majority of which could not be dissociated by the presence of HA10–50. These findings indicate that the large chondrotin sulfate proteoglycan synthesized by bovine collateral ligament may be a versican-like proteoglycan which exhibited the potential to form link protein-stabilized complexes.