Nuclear hormone receptor. Binds estrogens with an affinity similar to that of ESR1/ER-alpha, and activates expression of reporter genes containing estrogen response elements (ERE) in an estrogen- dependent manner (PubMed:20074560). {ECO:0000269|PubMed:20074560, ECO:0000269|PubMed:29261182, ECO:0000269|PubMed:30113650, ECO:0000269|PubMed:9325313}. [Isoform 2]: Lacks ligand binding ability and has no or only very low ERE binding activity resulting in the loss of ligand-dependent transactivation ability. . This is the function of ENSG00000140009 (ESR2, estrogen receptor 2).