Simple model of estrogen (E) and tamoxifen (T) binding to the ligand binding domain of the estrogen receptor (ER)

Basic model in which ligand (estrogen or tamoxifen) displaces heat shock protein (HSP), resulting in binding of ligand-receptor complex to estrogen receptor element (ERE) of gene promoter region. ER binding directly to the ERE is one mechanism, but ER can also instead tether DNA binding transcription factors for modulate genes without a classical ERE.