Estrogen receptor from human breast cancer and from normal human uterus: isolation and characterization of similar binding complexes.

Estrogen receptor from human breast cancer tissue and from normal human uterus was isolated and characterized by a combination of physical separation methods including ammonium sulfate precipitation, gel permeation chromatography, isoelectric focusing and gel electrophoresis. After incubation with 3H-estradiol-17 beta (3HE2) followed by gel permeation chromatography, specific estrogen-binding activity was found to be present in a 160,000-dalton molecular weight component which had a pI of 7.1-7.3. On polyacrylamide gel electrophoresis this estrogen-binding protein migrated as a single band which could however be dissociated into two subunits with molecular weights of +/- 60,000 and +/- 75,000 daltons. 3HE2 binding was to the 75,000-dalton component.