In a system of purified components , binding of a DNA fragment containing a ER6 pregnane X response element from __SP__ __NODE__ gene and a protein protein complex consisting of __SP__ __NODE__ and of __SP__ __NODE__ is greater than binding of a DNA fragment containing a ER6 pregnane X response element from __SP__ __NODE__ gene and a protein protein complex consisting of __SP__ __NODE__ and of __SP__ __NODE__ .