Estrogen-binding protein from rat preputial gland: purification and characterization.

Cytosol from the rat preputial gland has been shown to contain a protein which binds both estrone and estradiol. The protein, after a 26-fold purification from the cytosol of female Sprague-Dawley rats, migrated as one band during electrophoresis in sodium dodecyl sulfate on acrylamide gel. The electrophoretic mobility indicated a molecular weight of 15,000. The association constant for estrone as determined by equilibrium dialysis was 1.2 X 10(7) M-1, while that for 17beta-estradiol was 3.3 X 10(6) M-1. Progesterone, cortisol, testosterone, or diethylstilbestrol did not bind to the purified protein, whereas 17alpha-estradiol or estriol bound only slightly. In the presence of retinoic acid, but not retinol, the binding of estrone was reduced. Optimum binding for estrone was at pH 6.5 to 8.5.