The androgen receptor belongs to the superfamily of nuclear receptors, which are ligand-dependent transcription factors. In the absence of the androgen, the receptor is localized to the cytoplasm where it is associated with heat shock proteins. Upon ligand binding, the receptor translocates into the nucleus and interacts with specific DNA sequences, called androgen response elements. The DNA-bound receptor interacts with the transcription initiation complex to regulate transcription.
The structural organization of the androgen receptor is very similar to the other members of the steroid receptor family, with an N-terminal transcriptional regulatory domain, a centrally positioned C2C2 zinc finger DNA binding domain, and a C-terminal ligand binding domain. The N-terminal domain contains a polymorphic polyglutamine tract encoded by a trinucleotide (CAG) repeat; the polyglutamine tract normally consists of 9–36 glutamines. Pathological expansion of the androgen receptor polyglutamine tract to 40–62 glutamines causes spinal and bulbar muscular atrophy, a slowly progressive, X-linked motor neuron disease.