Figure 4.
Activation of protein C requires cleavage by a proprotein convertase before that of thrombin. WT protein C and its processing site mutants (PCs site R198A, thrombin site: R221A) were co-expressed in COS-1 cells with either an empty vector or one encoding PC5/6A. A, Western blot showing the production and processing of protein C in 24-h conditioned media. B, protein C activity was assessed using a chromogenic substrate and a ProtAc, and the data are expressed as arbitrary units (AU)/min × 10−3. These data are representative of four independent experiments.