Binds estrogens with an affinity similar to that of ER-alpha, and activates expression of reporter genes containing estrogen response elements (ERE) in an estrogen-dependent manner. Binds DNA as a homodimer. Can form a heterodimer with ER-alpha (By similarity). Composed of three domains: a modulating N-terminal domain, a DNA-binding domain and a C-terminal ligand-binding domain. Belongs to the nuclear hormone receptor family. NR3 subfamily.