Effect of GFD and ATF on the binding of scuPA linker mutants to suPAR measured as surface plasmon resonance. Binding of scuPA-Lys48Pro (A-B) and scuPA-Ser47Gly (C-D) to recombinant suPAR was monitored as described in the legends to Figures 2 and 5. (A,C) Buffer was injected for 3 minutes (no wash) followed by 2 nM scuPA-Lys48Pro (A) or scuPA-Ser47Gly (C) for 3 minutes with a 3-minute wash delay (black); 400 nM GFD was injected for 3 minutes (no wash) followed by a mixture of 400 nM GFD plus 2 nM scuPA mutant for 3 minutes with a 3-minute wash delay (gray). (B,D) Buffer was injected for 3 minutes (no wash) followed by 2 nM scuPA-Lys48Pro (B) or scuPA-Ser47Gly (D) for 3 minutes with a 3-minute wash delay (black); 400 nM ATF was injected for 3 minutes (no wash) followed by a mixture of 400 nM GFD plus 2 nM scuPA mutant for 3 minutes with a 30-minute wash delay (gray).