Binding of sDI to DII+DIII-uPAR in the presence of scuPA kringle mutants. Binding of ¹²⁵I-sDI (50 nM) to 293 cells expressing GPI-anchored uPAR DII+DIII was measured in the presence of the indicated (0 to 400 nM) concentrations of WT-scuPA (▪), scuPA-Lys105-110Ala (□), scuPA-Lys107-109Ala (▴), scuPA-Lys108-110Ala (×), scuPA-Lys110Ala (○), and scuPA-Lys107Ala (•). Binding was measured as described in the legend to Figure 7. The data shown are from a single experiment representative of 2 so performed.