Biochemical and immunological evidence that an acidic domain of hsp 90 is involved in the stabilization of untransformed glucocorticoid receptor complexes.

Polyclonal antibodies (AS 232-266) have been raised against the 232-266 amino acid sequence of the mouse hsp 84. This sequence possesses 54% acidic residues. AS 232-266 react with both the denatured and the free native murine hsp 84, but not with the bound hsp 84 present in the untransformed glucocorticoid receptor complexes (GR). Both AS 232-266 and peptide 232-266 were shown to decrease [3H]dexamethasone binding by GR. Moreover synthetic peptide 232-266, when added to 7 nm untransformed GR, convert them into 5 nm hsp 84-free GR. Taken together these data suggest that the acidic 232-266 sequence of hsp 84 is involved in the stabilization of the hsp 84-GR interaction, which is known to result in 7 nm complex formation and in GR ligand binding activity improvement. Both peptide 232-266 and AS 232-266 destabilize this interaction.