Physicochemical properties of type I corticosteroid receptors from rat brain

[3H]Aldosterone binds with high affinity to Type I corticosteroid receptors in cytosols from adrenalectomized rat forebrains. Physicochemical parameters of these receptors were determined in the presence of molybdate, which stabilized receptors and maintained them in a presumably untransformed state. The Stokes' radius of the molybdate-stabilized receptor was 8.1 nm, as determined by gel filtration on Sephacryl S-300. Its sedimentation coefficient was 9.1S in linear sucrose density gradients. The receptor is asymmetric, with an axial ratio of 8-10 and an apparent mol. wt of 303,000 dalton. The [3H]aldosterone-receptor complex is anionic and elutes from DEAE-Trisacryl in a single peak with a maximum at 160 mM KCl. Exposure to heat or salt in the absence of molybdate, conditions which transform other steroid receptors to smaller DNA-binding forms, causes marked instability of the [3H]aldosterone-receptor complex. The [3H]aldosterone-binding protein of rat forebrain, which displays the binding characteristics of a renal Type I (mineralocorticoid) receptor, is similar in size, shape and charge to the molybdate-stabilized oligomeric forms of other steroid hormone receptors.