Effects of Sodium Molybdate on the Androgen Receptor from the R3327 Prostatic Tumor*

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Abstract
The effects of sodium molybdate on several physicochemical properties of the androgen receptor from the Dunning R3327 prostatic tumor were studied. Molybdate stabilized the steroid-binding activity of the receptor. Maximum binding activity was found with concentrations of 10 mM molybdate or greater. Density gradient and gel filtration analyses of the receptor revealed an 8.5-9.0S, 68 .ANG. form (MW .apprx. 265,000-275,000) in either the presence or absence of molybdate (20 mM) when determined under low ionic conditions. Under high ionic conditions (400 mM KCl), the receptor was maintained in a similar form (8.5-9.0S; 72-73 .ANG.; MW .apprx. 275,000-295,000) in the presence of molybdate; however, it disaggregated to a smaller 4.4S, 61 .ANG. form MW .apprx. 120,000) in the absence of molybdate. Affinity labeling of the receptor with 17.beta.-[(bromoacetyl)oxy]-[1,2,4,5,6,7,16,17-3H8]5.alpha.-androstan-3-one showed a MW of 118,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. Molybdate inhibited the salt-induced transformation of the receptor of a DNA-binding state, but did not inhibit the DNA binding of the receptor transformed previously in the absence of molybdate. Sodium molybdate may stabilize the steroid-binding activity of the androgen receptor in an aggregated nontransformed state.