Binding of rSp17 to cells is dependent on cell surface heparan sulfate.

The rSp17 (50 μg/mL) was added to ARP-1 cells and the level of Sp17 determined by flow cytometry following immunostaining. Data are expressed as a percentage of control, where the control was the value of staining for Sp17 in the absence of rSp17. Prior to addition of rSp17, some cells were treated with chondroitinase ABC (ABC'ase), to remove chondroitin sulfate chains, or heparitinase (hep'ase), to remove heparan sulfate chains. Removal of chondroitin sulfate chains has no effect on binding of rSp17 to cells. However, in comparison with these cells, removal of heparan sulfate significantly (P < .03) reduces the amount of rSp17 bound to cells. Values represent the mean of 3 experiments ± SE. (Insert) The rSp17 used in these experiments was purified as described in “Materials and methods” and analyzed for purity by Western blotting. The rSp17 is detected with antiserum as a 24.5-kd protein (arrowhead).