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

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.