Domain structure of nuclear receptors. The nuclear receptor superfamily proteins have several functional domains; the activation function 1 (AF1) domain at the N terminus, the DNA-binding domain (DBD), a hinge region, a ligand-binding domain (LBD) and another activation function 2 (AF2) domain at the C terminus. The small heterodimer protein (SHP) that has a major role in the regulation of genes involved in bile acid synthesis and transport, lacks the AF1 and DBD domains. Derived in part, with permission, from Science Slides (scienceslides.com).