Fig. 4.
Inhibitory activity of the IMPI mutants. (A) Relative fractional activity as Vi/V0 of 50 nM aureolysin after incubation with IMPI mutants, relative to the wild type at molar ratios 1:1, 1:5, 1:10, 1:50 and 1:100 with FRET-4 (at 20 μM) as the substrate. Experiments were performed at least in triplicate, and error bars show standard deviations. (B) Tabular representation of the relative aureolysin activity data (in %) shown in (A). Average half-maximal inhibitory concentrations (IC50) were determined using a four-parameter sigmoidal fit in GRAPHPAD (see Suppl. Fig. 2), and the inhibitor constant Ki was estimated usinf the equation Ki = IC50/([S]/KM + 1) [93].