FIG 7.

Aprotinin inhibits the activity of CroP present at the OM. (A) Production of CroP by C. rodentium wild type was quantified by densitometry analysis of Western blots by comparing to a standard curve of purified CroP. Western blots were performed in triplicate with the anti-CroP antibody. In the resulting standard curve of purified CroP (solid circles and line of best fit), data are expressed as means ± the SEM. The concentration of CroP in C. rodentium wild-type was interpolated from the standard curve (open circle and vertical line). AU, arbitrary units. (B) FRET assays were performed with wild-type C. rodentium cells in the presence of increasing concentrations of aprotinin, as indicated. The percentage of CroP activity is expressed 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 < 0.01; ***, P < 0.001).