FIGURE 6.

Heparan sulfate chains from recombinant syndecan-4 are of similar size but different charge characteristics depending on the number of chains and site of substitution. Transfected COS7 cells were metabolically labeled with ³⁵SO₄ and the syndecan-4 purified by immunoprecipitation with anti-HA antibodies. Glycosaminoglycan chains were cleaved from the core protein and applied to gel filtration and ion exchange columns. In each case, the chains are of similar length regardless of whether derived from syndecan-4 bearing 1, 2, or 3 chains or their position on the core protein (A–G). However, ion exchange chromatography showed that the net charge characteristics of the chains on syndecan-4 depends both on their number and their position on the core protein (H–N). Chains substituted toward the N-terminal of core protein (L) are less charged than those more C-terminal (M and N). However, when multiple chains were expressed on the core protein, the charge density of all chains was proportionally higher (H–K). The salt concentrations corresponding to peak elution of each sample are noted on each panel.