Ligand binding domain of the nuclear receptor androgen receptor, ligand activated transcription regulator
The ligand binding domain of the androgen receptor (AR): AR is a member of the nuclear receptor family. It is activated by binding either of the androgenic hormones, testosterone or dihydrotestosterone, which are responsible for male primary sexual characteristics and for secondary male characteristics, respectively. The primary mechanism of action of ARs is by direct regulation of gene transcription. The binding of an androgen results in a conformational change in the androgen receptor which causes its transport from the cytosol into the cell nucleus, and dimerization. The receptor dimer binds to a hormone response element of AR-regulated genes and modulates their expression. Another mode of action is independent of their interactions with DNA. The receptors interact directly with signal transduction proteins in the cytoplasm, causing rapid changes in cell function, such as ion transport. Like other members of the nuclear receptor (NR) superfamily of ligand-activated transcription factors, AR has a central well conserved DNA binding domain (DBD), a variable N-terminal domain, a flexible hinge and a C-terminal ligand binding domain (LBD). The LBD is not only involved in binding to androgen, but also involved in binding of coactivator proteins and dimerization. A ligand dependent nuclear export signal is also present at the ligand binding domain.