Resolution of activated and unactivated forms of the glucocorticoid receptor from rat liver

Abstract

Two forms of rat liver glucocorticoid receptor corresponding to the unactivated and activated states of the receptor were separated by rapid ion exchange chromatography on minicolumns of diethylaminoethyl (DEAE)-Sephadex and carboxymethyl (CM)-Sephadex. The more acidic form (D A) required a very high salt concentration to be eluted from DEAE-Sephadex and has not been reported previously. The identity of this form with the unactivated receptor which will not bind to CM-Sephadex (C A) was established. The more basic form (D B = C B), which was eluted at a lower salt concentration (0.18 m) from DEAE-Sephadex, could also bind to CM-Sephadex, indicating the presence of both positively and negatively charged regions on its surface. Since it was more easily eluted from CM-Sephadex than from DEAE-Sephadex, it was probably an acidic protein with a localized basic region. D A was converted to D B by heat and at 0 °C under the conditions associated with the Chromatographie procedure. The conversion was augmented in the presence of Tris buffer at higher pH but inhibited by phosphate buffer at a reduced pH.