The DNA-binding domain of vitamin D receptors (VDR) like nuclear receptor family is composed of two C4-type zinc fingers
The DNA-binding domain of vitamin D receptors (VDR) like nuclear receptor family is composed of two C4-type zinc fingers. Each zinc finger contains a group of four Cys residues which co-ordinates a single zinc atom. This domain interacts with specific DNA site upstream of the target gene and modulates the rate of transcriptional initiation. This family includes three types of nuclear receptors: vitamin D receptors (VDR), constitutive androstane receptor (CAR) and pregnane X receptor (PXR). VDR regulates calcium metabolism, cellular proliferation and differentiation. PXR and CAR function as sensors of toxic byproducts of cell metabolism and of exogenous chemicals, to facilitate their elimination. The DNA binding activity is regulated by their corresponding ligands. VDR is activated by Vitamin D; CAR and PXR respond to a diverse array of chemically distinct ligands, including many endogenous compounds and clinical drugs. Like other nuclear receptors, xenobiotic receptors have a central well conserved DNA binding domain (DBD), a variable N-terminal domain, a flexible hinge and a C-terminal ligand binding domain (LBD).