Identity of the protein cores of the two link proteins from bovine nasal cartilage proteoglycan complex. Localization of their sugar moieties.

The cyanogen bromide (CNBr) fragments of the two link proteins (LP) were examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The observed apparent molecular weight difference between LP1 (Mr = 44,500) and LP2 (Mr = 48,500) was the reflect of a molecular weight difference between their NH2-terminal CNBr fragments (Mr = 19,000 and 24,000 for LP1 and LP2, respectively). The latter are glycosylated contrary to the COOH-terminal parts of the molecules. Fluorhydric acid/pyridine treatment suggests that LP1 and LP2 have a protein core of identical size. They differ from their common tryptic fragment (T-G200-3 fraction) by the presence of an additional short peptide. The latter was highly glycosylated in LP2 but not in LP1. Deglycosylation together with CNBr treatment corroborates the hypothesis that LP1 and LP2 possess a similar protein core.