Purification and Characterization of a Nonhormone-Binding Component of the Nontransformed Glucocorticoid Receptor from Rat Liver1

The nontransformed glucocorticoid receptor (GR) and an 88-kDa protein in rat liver cytosol were selectively adsorbed on protamine- and arginine-Sepharose. The 88-kDa protein was purified from rat liver cytosol to homogeneity by precipitation with protamine sulfate, followed by DEAE-ion exchange chromatography, gel chromatography, and DEAE ion-exchange high-performance liquid chromatography. The 88-kDa protein appeared to be present as a dimer at both low and high salt concentrations. The physicochemical properties and the amino acid composition of the 88-kDa protein were almost the same as those of heat-shock protein 90 of HeLa cells and yeast. Preincubation of the GR with the polyclonal antibody raised against the 88-kDa protein increased the sedimentation coefficient of the nontransformed GR, but did not change that of the transformed GR. These results indicate that heat-shock protein 90 is associated with rat liver nontransformed GR and is responsible for the interaction of GR with protamine.