Fig. 2. MtrR binding to the steroids Progesterone, β-Estradiol, Testosterone, and Ethinyl Estrogen.

A Representative Isothermal titration calorimetry thermograms and binding isotherms of each natural steroid and ethinyl estradiol. At least three experimental measurements, technical and some biological replicates, were averaged for each reported binding constant. B Fluorescence polarization-based DNA-binding isotherms reveal significant decreases in the binding affinity of MtrR for the rpoH and mtrCDE operators in the presence of each gonadal steroid. Data are represented by the mean values (point) +/- SEM (error bar) of at least three independent experimental measurements and were averaged for each reported binding constant.