FIGURE 1.

Human C1-INH-degrading ability of S. pyogenes SpeB. A, supernatants obtained from strain SSI-9 (lane 2) and isogenic mutant of ΔspeB (lane 3) or ΔscpA (lane 4) and recombinant ScpA (lane 5) and SpeB (lane 6) proteins were separately incubated with human serum (without complement inactivation) for 3 h at 37 °C. The C1-INH was detected by Western blotting. M, molecular mass marker. Lane 1, mixture of human serum and PBS as positive control. B, human serum (without complement inactivation) was incubated with SSI-9 (lane 2) or rSpeB (serially diluted 2-fold with PBS) (lanes 3–10) for 1 h at 37 °C. The C1-INH was detected by Western blotting.