CHARACTERIZATION OF THE MEMBRANOUS ANTIESTROGEN BINDING-PROTEIN .1. PARTIAL-PURIFICATION OF THE PROTEIN IN ITS ACTIVE STATE

We previously demonstrated that, in addition to the estrogen receptor, the Antiestrogen Binding Site (ABS) is also a potent mediator of the antitumorous activity of the clinical drug tamoxifen. Because of reported discrepancies in the binding parameters of I at liver ABS we first attempted to improve binding study conditions. In this way buffer, protein concentration, methodology for bound/free ligand separation and phospholipidic ratio were determined. This work was used to evaluate the Stoke radius (4.4 S) and isoelectric point( pH=6.6) of the protein in its native state. These studies constituted the obligatory transition from rat liver to pure ABS protein.