FIG. 1.

Concentration-dependent effect of staphylococcal proteinases on the antibacterial activity of LL-37. LL-37 (3 mg/ml) was mixed with an equal volume of aureolysin (A and B) or the V8 protease (C and D) in 20 mM Tris, pH 7.8, with 1 mM CaCl₂ to yield indicated concentrations of both proteinases. The digested samples were tested for antibacterial action against S. aureus strain Newman (A and C) and E. coli ATCC 33694 (B and D). The diameter of the bacterial growth inhibition zones was measured and converted into units (0.1 mm = 1 U of inhibition growth). Each point in the figure represents a mean ± standard deviation of at least two independent triplicate assays. Insets in panels C and D show representative results of bacterial growth inhibition by LL-37 alone and after preincubation with two different concentrations of the V8 protease.