The plasminogen activator activity of scuPA/suPAR is fibrin dependent. (A) scuPA/suPAR (50 nM) was incubated with ¹²⁵I-fibrin clots or ¹²⁵I-globin in presence of 1 μM Glu-plasminogen and in the presence or absence of human serum. (B) The same experiment was performed except that tcuPA (25 nM) was added instead of the scuPA/suPAR complex. The 100% point represents fibrinolysis induced by scuPA (A) or tcuPA alone (B). In this and in all experiments that follow, the mean ± SD of 3 separate experiments is shown unless stated otherwise.