Effect of protein S and protein S-C4BP on APC-mediated inactivation of factor Va and factor VaLeiden in a reconstituted model system. (A) Inactivation of factor VaLeiden by APC (△), APC and 200 nM protein S (○), and APC and 200 nM protein S-C4BP (●). Loss of factor Va activity (stability) in the absence of APC (▲). (B) Inactivation of factor Va with APC (△), with APC and 200 nM protein S (○) and with APC and 200 nM protein S-C4BP (●). Loss of factor Va Leiden activity (stability) in the absence of APC (▲). (C) Superose-6 size-exclusion chromatography of incubation mixtures from B: factor Va, APC, and 200 nM protein S: protein S was measured by ELISA (▲); factor Va, APC, and 200 nM protein S-C4BP: protein S-C4BP (●) and protein S (△) were measured by ELISA.
