Effects of mutating the CRAC-like region on the binding of CdtC and CDT holotoxin to cells.

<p>CHO-K1 cells were treated with 200 nM of (A) CdtC^wt, (B) CdtC^Y81P, (C) CdtABC^wt, or (D) CdtABC^Y81P at 4°C for 2 h. The cells were washed and probed with control preimmune serum (gray histograms) or antisera against CdtC (A, B) or CdtB (C, D) (white histograms), followed by staining with Alexa Fluor 488-conjugated anti-mouse IgG. The binding activity was analyzed by flow cytometry. The numbers represent the mean channel fluorescence (MCF). The quantitative data represent the mean and standard deviation values from 3 independent experiments (E, F). The asterisks indicate statistical significance (*<i>P</i><0.05).