Further characterization of the estrogen binding macromolecule in human pancreas

The estrogen binding protein in human pancreas has been purified from pancreatic cytosol by chromatography on Concanavalin-A-Sepharose and hydroxyl-apatite followed by ion-exchange chromatography carried out using a fast-protein liquid chromatography apparatus (FPLC). The purified protein, still able to bind labelled [3H]estradiol, appeared as one single band corresponding to 31 K in SDS-gel electrophoresis. Total amino acid analysis revealed high levels of histidine, glutamic acid and leucine. The capacity of the purified protein to bind estrogens could be increased more than 4-fold by addition of a cytosolic factor, probably being a small peptide, that is present in crude cytosol, but lost during the purification procedure. The iodinated protein does not bind to DNA-cellulose or phosphocellulose, and shows no similarities to estrogen receptor proteins.