The molybdate-stabilized nonactivated glucocorticoid receptor contains a dimer of Mr 90,000 non-hormone-binding protein

A glucocorticoid receptor-associated Mr approximately 90,000 non-hormone-binding protein was purified and characterized. The molybdate-stabilized nonactivated rat liver glucocorticoid-receptor complex (Mr approximately 300,000) was immunoadsorbed on cyanogen bromide-activated Sepharose 4B to which a monoclonal IgG 2a antibody directed against the activated rat glucocorticoid receptor (Mr approximately 94,000) had been coupled. Following removal of molybdate and thermal activation of the receptor immobilized on the immunoaffinity matrix, an Mr approximately 90,000 non-hormone-binding protein was specifically eluted. This protein was further purified to homogeneity using high performance ion exchange chromatography and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, sucrose gradient ultra-centrifugation, and high performance size-exclusion chromatography. Hydrodynamic characterization under nondenaturing conditions revealed that the purified glucocorticoid receptor-associated protein represents a molecular species with a sedimentation coefficient of 6.1 S, a Stokes radius of 6.9 nm, and a calculated Mr approximately 184,000. These results, combined with analysis on denaturing electrophoresis indicate that, under certain conditions, the Mr approximately 94,000 steroid-binding protein is associated with a dimer of Mr approximately 90,000 non-hormone-binding protein.