Effect of protein S and protein S-C4BP on APC-mediated inactivation of recombinant factor Va (R³⁰⁶/R⁶⁷⁹Q and R⁵⁰⁶Q/R⁶⁷⁹Q) in a reconstituted model system. (A) Inactivation of recombinant factor Va (R³⁰⁶Q/R⁶⁷⁹Q) with APC (△), with APC and 200 nM C4BP (▽ dashed line) with APC and 200 nM protein S (○), with APC and 200 nM protein S-C4BP (●), and without APC (▲). (B) Inactivation of recombinant factor Va (R⁵⁰⁶Q/R⁶⁷⁹Q) with APC (△), with APC and 200 nM C4BP (▽ dashed line), with APC and 200 nM protein S (○), with APC and 200 nM protein S-C4BP (●), and without APC (▲).