Omptin procoagulant activity is mediated through direct TFPI inactivation. (A) Plasmin does not contribute to TFPI inactivation. Clotting times (measured as in Figure 1B) were obtained for mixtures of TFPI and various bacterial strains (108 cfu/mL) incubated in normal plasma (■) as well as in plasminogen-deficient plasma (□). TFPI activities were determined by reference to a standard curve of clot times versus TFPI concentration. (B-D) Omptin activity toward extrinsic clotting factors. Omptin-positive (■, E coli MC4100, S Typhimurium ΔgalETK, and Y pestis KIM5) and omptin-negative (□, E coli ΔompT, S Typhimurium ΔgalETK ΔpgtE, and Y pestis Δpla) bacterial strains were tested in clotting factor assays to measure changes in the specific coagulant activity of (B) prothrombin, (C) FV, (D) FVII, or (E) FX. Data are mean plus SEM (n = 3).
