title: Stabilization and characterization of the dexamethasone-binding proteins in rat liver cytosol.
abstract: Conditions were worked out for maximal stabilization of dexamethasone binding activity of rat liver cytosol in the absence of the protective steroid ligand. Important stabilization factors are ionic strength, thiol-protecting agents, glycerol and pH. Maximal stability of the cytosol is observed in a buffer consisting of 20 mM Tris-HCl, pH 7.5, 50 mM KCl, 25 mM beta-mercaptoethanol and 20% glycerol. Chromatography of cytosol on DEAE-cellulose revealed the existence of three dexamethasone receptors, binder DE-1, present in the flow-through fraction and binders DE-2 and DE-3, eluting from the column with salt concentrations of 100 and 190 mM, respectively. Binders DE-2 and DE-3 are not adsorbed on phosphocellulose at pH 7.5, whereas binder DE-1 is. All three receptors are retained to varying degrees on DNA-cellulose columns: binder DE-1 is eluted with salt concentrations of 270 mM, whereas binders DE-2 and DE-3 are eluted between 180 and 200 mM NaCl. The dexamethasone receptors also bind natural glucocorticoids, but to varying degrees, the highest binding being observed to binder DE-2. The receptors obtained after chromatography on DEAE-cellulose, but not on phosphocellulose, cannot be to an appreciable extent charged with dexamethasone.
mesh_terms: D000818:Animals; D002846:Chromatography, Affinity; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D003907:Dexamethasone / Q000378:metabolism*; D006207:Half-Life; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D009994:Osmolar Concentration; D011506:Proteins / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D011956:Receptors, Cell Surface / Q000187:drug effects; D013438:Sulfhydryl Compounds / Q000494:pharmacology
chemical_list: D011506:Proteins; D011956:Receptors, Cell Surface; D013438:Sulfhydryl Compounds; D003907:Dexamethasone