Evolution of pharmacologic specificity in the pregnane X receptor

In contrast to other nuclear hormone receptors, PXRs show significant differences in ligand specificity across species. By pharmacophore analysis, certain PXRs share similar features such as human, mouse, and rat PXRs, suggesting overlap of function and perhaps common evolutionary forces. The Western clawed frog PXR, like that described for African clawed frog PXRs, has diverged considerably in ligand selectivity from fish, bird, and mammalian PXRs.