Fig. 1.

A, comparison of the structures of human PXR.1 and PXR.2. PXR.2 lacks 111 nucleotides, resulting in a deletion of 37 amino acids from the LBD as shown in the gray-shaded region. Three active site residues that line the ligand-binding pocket of PXR.1 and that form contacts with SR12813 are missing from PXR.2. B, amino acid sequence alignment of the LBDs of human PXR.1 and PXR.2. Structural elements (α helical regions and β strands) and several amino acids important for homodimerization (arrows) are indicated.