Molecular properties of the androgen receptor in rat ventral prostate.

Results from these studies demonstrate that we have purified a protein from rat prostate cytosol that is similar to the beta-protein (complex II) but different from the alpha-protein (complex I) reported by Liao et al. The purified receptor was different from androgen binding protein (ABP) in that ABP has a faster dissociation rate (6 min), a lower pI value (4.6), and requires higher concentrations of ammonium sulfate for precipitation (40-50%) than the prostatic androgen receptor. It is not likely that we have purified a serum sex-steroid binding protein since no such protein is found in rat serum. This report presents a rapid and efficient procedure for the purification of androgen receptor from rat ventral prostate. However, the present procedure only allowed us to obtain a limited quantity of purified receptor from each preparation. It is obvious that we need to scale up the purification of the receptor in order to study in detail its physicochemical properties and to produce monospecific antibodies against the protein. This work is in progress. In addition, we have demonstrated that two affinity labels can be used to bind covalently to the androgen receptor. Most importantly, these compounds can be used to characterize androgen receptors under both nondenaturing and denaturing conditions and represent useful tools for future work with androgen receptor proteins and androphilic proteins in general.