5β-Cholestan-3α,7α,12α-triol and 7α-hydroxy-4-cholesten-3-one directly bind mouse PXR as determined by fluorescence polarization assay. A fluorescein-tagged SRC1 peptide (ILRKLLQE) was incubated with bacterially expressed, purified GST-mPXR (black bars) or GST (white bars) in the presence of vehicle (DMSO), PCN (10 μM), or bile acid intermediates at 10 μM. Ligand-induced recruitment of the fluorescein-tagged SRC1 peptide was monitored by an increase in millipolarization fluorescence units (mP). Data shown represent the mean ± SEM of six samples.