Fig 3. Short-chain polyphosphates accelerate the inhibition of TFPIα by FXIa.

(A) TFPIα (10 nM) was pretreated with FXIa (2 nM) in the absence or presence of 25 μM Zn²⁺, 10 μM platelet-size polyphosphate (SCP), or Zn²⁺ and SCP. After 30 min of incubation with FXIa, aprotinin (50 μM) and polybrene (16 μM) were added to all samples to stop the reaction. FXa generation by the TF-FVIIa complex in the presence of different concentrations of TFPIα was measured. (B) TFPIα (10 nM) was pretreated with different concentrations of FXIa in the presence of 25 μM Zn²⁺ and 10 μM SCP. After 30 min of incubation with FXIa, aprotinin (50 μM) and polybrene (16 μM) were added to all samples to stop the reaction and FXa generation by the TF-FVIIa complex in the presence of different concentrations of TFPIα was measured. (C) TFPIα (10 nM) was pretreated with 4 nM FXIa^ABS in the presence of 25 μM Zn²⁺, 10 μM SCP, or Zn²⁺ and SCP. After 30 min of incubation with FXIa^ABS, aprotinin (50 μM) and polybrene (16 μM) were added to all samples to stop the reaction and FXa generation by the TF-FVIIa complex in the presence of different concentrations of TFPIα was measured. Data are mean ± SE (n = 3).