Pregnane X Receptor is a ligand-activated transcription factor critical in protecting tissues from xenobiotics and endobiotics. PXR is shown to interact with GRIP- 1 and PGC-1α on DR-4 and XREM-CYP3A4 promoters. Experiments with full-length PXR have been limited by the inability to produce it. This study reports production of full-length PXR from Spodoptera frugiperda and use in peptide phage display experiments. PXR LBD was also mapped using peptide phage display. Sequencing results demonstrate a conserved motif consistent with class II nuclear receptor boxes but adding an additional residue, a polar residue in the -3 position. There is a novel intermolecular β-sheet mediating homodimerization in all PXR LBD structures. Mammalian two-hybrid studies demonstrated that a mutant of PXR that disrupts the homodimerization interface and eliminates basal transcriptional activity is unable to recruit SRC-1. Thermal denaturation studies of other PXR LBD mutants that affect basal transcriptional activity show changes in overall protein stability.