APC cofactor activities of FV variants as elucidated by FVIIIa degradation.

Increasing amounts of FV (final concentration, 0.1-0.9 nM) were mixed with APC (final concentration, 2.0 nM) and protein S (final concentration, 2.5 nM). Preformed tenase complexes containing phospholipid-bound FIXa and FVIIIa were added, and the FVIIIa degradation was followed. (closed circle) WT FV; (closed triangle) FV 306G; (open triangle) FV 306T; (open diamond) FV 306Q; (open square) FV 506Q; (closed square) FV506Q/679Q.