Stabilization of 8S progesterone receptor from human prostate in the presence of molybdate ion.

Abstract

In the presence of 10 mM molybdate ion, we are able to detect the appearance of a [6,7-3H]-17,21-dimethyl-19-nor-4,9-pregnadiene-3,20-dione-([3H]R5020) binding moiety in human prostatic cytosol which sedimented at approximately 8S in a glycerol density gradient. The specifically bound [3H]-R5020 was displaced by progesterone, tiramcinolone acetonide, and R5020 but not by cortisol, dihydrotestosterone, 17 beta-estradiol, or diethylstilbestrol. Specific binding of [3H]R5020 in the presence of molybdate ion was shown to saturate at 7 x 10(-10) M (n = 64 fmol/mg of protein). The optimum concentration of molybdate ion for enhancing specific binding of [3H]-R5020 was determined to be between 7 and 20 mM. Molybdate ion was also effective in stabilizing the 8S R5020-binding moiety in a preincubation for 16 hr at 0 degrees in the absence of added steroid.