This domain family is found in eukaryotes, and is approximately 110 amino acids in length. The family is found in association with pfam00104, pfam00105. There is a conserved IPS sequence motif. There are two completely conserved residues (Y and W) that may be functionally important. ERbeta binds estrogens with an affinity similar to that of ERalpha, and activates expression of reporter genes containing estrogen response elements in an estrogen-dependent manner. ERbeta acts as a transcription factor once bound to its ligand and it can dimerize with ERalpha.