Figure 1.

Factor XII-W268R displays spontaneous activity during protein expression. A, Western blotting of expression medium under reducing (R) conditions. The closed arrow indicates the FXIIa light chain. The image is representative of three separate experiments. B, chromogenic substrate assay for FXIIa activity in expression medium. C, quantification of FXIIa activity in expression medium. Substrate conversion (linear) was monitored in the first 20 min of the assays and fitted to a standard curve of αFXIIa in expression medium. D, chromogenic substrate assay for plasma prekallikrein activator activity in expression medium. E, effects of PPACK, C1-INH, or antibody OT2 on FXIIa activity in expression medium. F, FXIIa–C1-INH complex formation in expression medium. After incubation with C1-INH, a sigmoidal 4PL fit model was used to interpolate concentrations from a standard curve. The figure panels represent means and S.D. of three repeated experiments.