APC cleavage of Arg306. Recombinant FV variants (0.8 nM) were activated with thrombin as described in Figure 3. APC and 10:20:70 PS/PE/PC phospholipids (final concentration, 25 μM) were then added with or without protein S. (A) In the absence of protein S. Final APC concentration was 1.3 nM. FVa-Arg506Gln/Arg679Gln, □; FVa-Ile359Thr/Arg506Gln/Arg679Gln, ▴; controls without APC, FVa-Arg506Gln/Arg679Gln, ○; FVa-Ile359Thr/Arg506Gln/Arg679Gln, . (B) APC degradation in the presence of protein S (final concentration, 100 nM). Final concentration of APC was 0.05 nM. FVa-Arg506Gln/Arg679Gln, □; FVa-Ile359Thr/Arg506Gln/Arg679Gln, ▴.