FIG 4.

Inhibition of CroP activity by aprotinin. (A) Aprotinin inhibits cleavage of the FRET substrate by purified CroP. FRET assays were performed with 10 nM CroP in PBS (black) or in the presence of EDTA (2.5 mM, green), PMSF (2.5 mM, purple), leupeptin (10 μM, blue), pepstatin A (10 μM, red), or aprotinin (10 μM, orange). RFU, relative fluorescence units. The data shown are representative of three independent experiments performed in triplicate. (B) Inhibition of purified CroP by aprotinin is dose dependent. FRET assays were performed with 10 nM CroP in the presence of increasing concentrations of aprotinin, as indicated. The percentage of CroP activity is relative to the uninhibited reaction. The results are expressed as means ± the SEM of triplicate samples and are representative of three independent experiments. Statistical significance was assessed by one-way analysis of variance, followed by Dunnett's post hoc test (***, P < 0.001).