GST (pcDNA3.1-FLAG-GST) or GST-PXR LBD [pcDNA3.1-FLAG-GST-PXR LBD (WT, W299A, and W299D)] were expressed using the TNT Quick Coupled Transcription/Translation System (Promega); 1 μg of plasmid DNA was used for each 50 μL reaction, and the reactions were incubated at 30°C for 90 min. The TR-FRET binding assay has been described previously [30 (link)], and the protocol was modified for the in vitro protein expression method. Reactions (20 μL) contained 50 mM Tris (pH 7.5), 50 mM NaCl, 0.1 mg/mL bovine serum albumin, 5 nM LanthaScreen Tb-anti-GST Antibody (Thermo Fisher Scientific), 2 μL of protein expression reaction product, 1% DMSO, and the indicated concentrations of BODIPY FL vindoline. Reactions were incubated at RT in black 384-well low-volume assay plates for 30 min, and a PHERAstar FS plate reader (BMG Labtech) was used to detect the TR-FRET signals with the following instrumentation settings: a 340 nm excitation filter, a 100 μs delay time, and a 200 μs integration time. The TR-FRET ratio was expressed as 10,000 × 520 nm/490 nm, and values were normalized by subtracting the GST control signal at each point from the corresponding GST-PXR LBD signals.