Figure 4.

Inhibition of myosin-enhanced prothrombin activation by myosin HC peptides and their binding of factor Xa. Varying concentrations of peptides HC795–818 and HC816–837 were incubated with factor Va (5 nm final) and factor Xa (0.2 nm final) in TBSA plus 5 mm CaCl₂ at room temperature in the presence of skeletal muscle myosin (2 nm final) (A) or phospholipid vesicles (PC/PS, 80%/20%, w/w) (4 μm final) (B). Thrombin generation was then initiated by the addition of prothrombin (0.75 μm) in TBSA containing 5 mm Ca²⁺. The reaction was quenched by adding EDTA (10 mm final), and thrombin generation was determined as described under “Experimental procedures.” 100% was the value for controls in the absence of added peptides. C, peptides HC796–835, HC795–818, and HC816–837 were immobilized in microtiter plate wells, and the binding of factor Xa to HC796–835, HC795–818, and HC816–837 was determined as described under “Experimental procedures.” Each value represents the mean ± S.E. (error bars) of triplicate determinations.