Fig. 3.
Cantharidin-dose responses. Reactions containing recombinant phosphatase in the presence of the indicated concentrations of cantharidin were conducted as described in “Materials and Methods” section. Fluorescence intensity (485-nm excitation/525-nm emission) was measured every 30 s over 5 min with an M5 plate reader. Initial rates were determined from linear regression analyses of the raw fluorescence data with SoftMax Pro and the mean change in fluorescence over time (milli-RFU/min)±SD of six replicates was normalized to uninhibited controls and plotted as % inhibition versus cantharidin concentration. Inhibition curves were fit to a 4-parameter sigmoidal function with Prism® to estimate IC50s. (A) Inhibition curve of PP5C in the presence of cantharidin (IC50=328 nM; 95% CI: 271–396 nM). (B) Inhibition curve of PP1α in the presence of cantharidin (IC50=139 nM; 95% CI: 114–170 nM).