Interaction of the M(r) = 90,000 heat shock protein with the steroid-binding domain of the glucocorticoid receptor

We have investigated the physicochemical characteristics of trypsin-treated, molybdate-stabilized glucocorticoid-receptor complexes from rat liver in the presence of 10 mM sodium molybdate by high performance ion-exchange chromatography, high performance size-exclusion chromatography, and sedimentation analysis. Trypsin treatment was performed under conditions previously reported to degrade the monomeric M(r) ~ 94,000 steroid-binding protein to an M(r) ~ 27,000 ligand-binding entity (Wrange, O., and Gustafsson, J.-A. (1978) J. Biol. Chem. 253, 856-865). Also in the presence of molybdate, an M(r) ~ 27,000 steroid-binding fragment was obtained by limited trypsinization. However, no major differences in the tested physicochemical parameters were seen when trypsin-treated glucocorticoid-receptor complexes were compared with crude cytosolic complexes. Furthermore, the M(r) ~ 27,000 steroid-binding fragment generated in the presence of molybdate could be immunoprecipitated by antibodies specific for the glucocorticoid receptor-associated M(r) ~ 90,000 heat shock protein. These results provide direct evidence for an interaction of the M(r) ~ 90,000 heat shock protein with the steroid-binding domain of the glucocorticoid receptor, known to correspond to the C-terminal third of the receptor protein.