Binding of biotinylated SB105-A10 to HSPGs expressed at the cell surface. (A) Monolayers of wild-type CHO-K1 or HSPG-deficient CHO-K1 A745 cells were incubated with increasing concentrations of biotinylated SB105-A10. Alternatively, they were incubated with the peptide at 5 μg/ml and then washed with PBS alone or containing 2 M NaCl. (B) Monolayers of epithelial HL3T1 cells were incubated with increasing concentrations of biotinylated SB105-A10-polyethylene glycol. In parallel experiments, they were (i) pretreated with heparinase III (15 mU/ml) and incubated with biotinylated SB105-A10 (5 μg/ml); and (ii) incubated with biotinylated SB105-A10 (5 μg/ml) in the presence of heparin (10 μg/ml), incubated with biotinylated SB105-A10 (5 μg/ml) alone, and then washed with PBS containing 2 M NaCl. At the end of incubation, the amount of biotinylated SB105-A10 bound to cells was measured. Each point is the mean ± standard error of the mean for 3 or 4 determinations performed in duplicate.