Ecotin, a microbial inhibitor of serine proteases, blocks multiple complement dependent and independent microbicidal activities of human serum
Fig 5
E. coli ecotin inhibits FD-driven C3bBb-formation and C3bBb-mediated C3b-production.
Approximately 45% of C3 was cleaved when no inhibitor was present (positive control) (A). When no FB and FD were present, no C3-cleavage occurred (negative control) (B). In (C) the sample contained 10 μM E. coli ecotin, while in (D) 100 μM FUT. As the AP-type C3bBb C3-convertase has a short half-life, no C3-clevage occurs after 10 minutes (E), hence, we compared the amounts of C3b generated in 10 minutes after adding FD (F). At 10 μM, E. coli ecotin decreased the production of C3b by 20% (C, F), while at 100 μM, FUT, the small-molecule general complement-inhibitor, decreased C3b-production by 80% (D, F).