Physicochemical characterization of a new glucocorticoid receptor.
A new glucocorticoid-binding protein (Peak C) eluted with 0.14 M NaCl on DEAE-cellulose chromatography was identified previously in the rats subjected to stress or treated with glucocorticoid (100 micrograms/100 g body wt.), while the 'classic' glucocorticoid receptor (Peak B) eluted with 0.07 M NaCl was found predominantly in untreated rats. The new glucocorticoid-binding protein, Peak C, was characterized by Scatchard analysis and competition with other steroids as a glucocorticoid receptor. The saturation curve of Peak C for dexamethasone was sigmoidal, whereas that of Peak B was hyperbolic. The Hill coefficient was 1.0 for Peak B and 3.1 for Peak C. These results show that Peak C has multiple binding sites. Peak C bound specifically to only natural or synthetic glucocorticoids, whereas Peak B bound not only to glucocorticoids but also to progesterone and aldosterone. Peak C was far more labile than Peak B, its binding activity decreasing 80% when it was incubated for 30 min at 25 degrees C. The molecular sizes of these two peaks (B and C) were similar, being about 90 000-100 000 as determined by Sepharose 6B column chromatography at high ionic strength (0.34 M KCl). The hormone-receptor complex of Peak C bound to rat liver chromatin specifically, but did not bind to calf thymus DNA. The complex of Peak B bound to not only the chromatin but also calf thymus DNA. Peak B reacted well with antiserum to the 'classic' glucocorticoid receptor, but Peak C did not react with this antiserum. These results indicate that Peak C is a different glucocorticoid receptor protein from Peak B, or classic glucocorticoid receptor, and plays physiologically important roles as a glucocorticoid receptor mediating the action of the hormone at a high level.
D000818:Animals; D001667:Binding, Competitive; D002467:Cell Nucleus / Q000378:metabolism; D002482:Cellulose / Q000031:analogs & derivatives; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002843:Chromatin / Q000378:metabolism; D002848:Chromatography, DEAE-Cellulose; D003345:Corticosterone / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000031:analogs & derivatives; D003907:Dexamethasone / Q000378:metabolism; D005938:Glucocorticoids / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D008970:Molecular Weight; D051381:Rats; D011919:Rats, Inbred Strains; D011965:Receptors, Glucocorticoid / Q000378:metabolism*
D002843:Chromatin; C033190:DNA-cellulose; D005938:Glucocorticoids; D011965:Receptors, Glucocorticoid; D003907:Dexamethasone; D002482:Cellulose; D004247:DNA; D003345:Corticosterone