Figure 5

APC Inactivation of FVa in the Presence of a Saturating Concentration of FXa. Empirical: FVa (20 nM, Panels A-D) or FVa_i⁵⁰⁶ (20 nM, Panel E and F) was pre-incubated with active site blocked FXa* (30 nM) at 37°C. The reaction was then initiated with 2.0 nM APC. The inactivation of FVa was monitored by densitometry for the following fragments: FVa^HC (Panel A), FVa^1-506 (B), FVa^307-679/709 (C) and FVa^307-506 (D) and the inactivation of FVa_i⁵⁰⁶ was monitored by following FVa^1-506 (E) and FVa^307-506 (F). All data points with FVa are presented as averages ± S.D. of 4–6 experiments and data points with FVa_i⁵⁰⁶ are presented as averages ± S.D. of 2 experiments. Mathematical: Simulated time courses in which the model description does not allow APC proteolysis of the FXaFVa_i⁵⁰⁶ complex (dotted line) or allows the cleavage by APC at Arg³⁰⁶ in the FXaFVa_i⁵⁰⁶ complex with rate constants of 2.5 x 10⁶ M^-1 s^-1 (dashed line), 5.0 x 10⁶ M^-1 s^-1 (solid line), or 9.1 x 10⁶ M^-1 s^-1 (dash with dotted line).