Structure and function of the dioxin receptor: A DNA-binding protein similar to steroid hormone receptors

In analogy to steroid hormone receptors, the rat hepatic dioxin receptor binds to bulk DNA and heparin in vitro. The affinity of the dioxin receptor for both DNA and heparin is dependent on the binding of ligand and is negatively affected by the presence of sodium molybdate in the homogenization buffer. Limited proteolysis of the dioxin receptor with trypsin which is known to eliminate the DNA-binding property of the glucocorticoid receptor also resulted in a loss of DNA-binding activity and a decreased strength in the interaction with heparin of the in vitro liganded dioxin receptor. However, limited proteolysis with trypsin did not result in any change in gross structural properties of the dioxin receptor. These data suggest that the DNA-binding activity of the dioxin receptor resides within a discrete and relatively small functional domain of the protein.