The ligand binding domain of Farnesoid X receptor:a member of the nuclear receptor superfamily of ligand-activated transcription factors.The ligand binding domain (LBD) of Farnesoid X receptor: Farnesoid X receptor (FXR) is a member of the nuclear receptor superfamily of ligand-activated transcription factors. FXR is highly expressed in the liver, the intestine, the kidney, and the adrenals. FXR plays key roles in the regulation of bile acid, cholesterol, triglyceride, and glucose metabolism. Evidences show that it also regulates liver regeneration. Upon binding of ligands, such as bile acid, an endogenous ligand, FXRs bind to FXR response elements (FXREs) either as a monomer or as a heterodimer with retinoid X receptor (RXR), and regulate the expression of various genes involved in bile acid, lipid, and glucose metabolism. There are two FXR genes (FXRalpha and FXRbeta) in mammals. A single FXRalpha gene encodes four isoforms resulting from differential use of promoters and alternative splicing. FXRbeta is a functional receptor in mice, rats, rabbits and dogs, but is a pseudogene in humans and primates. Like other members of the nuclear receptor (NR) superfamily, farnesoid X receptors have a central well conserved DNA binding domain (DBD), a variable N-terminal domain, a non-conserved hinge and a C-terminal ligand binding domain (LBD).