Figure 2.

Anticoagulant co-factor activity of purified human and murine protein S. APTT clotting assays were performed using mouse (A) and human (B) plasma and increasing concentrations of human and murine APC in the absence or presence of recombinant human or murine protein S (48 nM) as indicated. For dose-response studies of protein S, FXa one-stage clotting assays were performed using 4 nM murine APC in mouse plasma (C) and 4 nM human APC in human plasma (D). The presence of human (□) or mouse (▪) protein S is indicated by the symbols in panels C and D. Each experiment was performed in triplicate and mean values with standard deviation are presented. The indicated concentrations of protein S represent the final concentrations in the clotting mixture.