Concentration and preservation of nuclear androgen receptor by lyophilisation

Nuclei from rat ventral prostate were disrupted by sonication and treated with micrococcal nuclease to precipitate nuclear proteins including the androgen receptor. The precipitate was dissolved in 0.6--1.2 M ammonium bicarbonate buffer, pH 7.6, with no loss of receptor when compared to the conventional Tes buffer, pH 7.0 containing 0.6--1.2 M NaCl. Lyophilisation of the solubilised protein did not produce any qualitative or quantitative differences in the recovery of receptor relative to a non-lyophilised control preparation, both of which were analysed for binding properties by Sephadex G-25/G-100 dual-column chromatography. Over longer periods of storage at -80 degrees C, the rate of inactivation of receptor was found to be 6% per week. The stability of the lyophilised receptor was improved by the inclusion of MgCl2 and SH-reducing agents in the ammonium bicarbonate buffer. Recovery improved also with increasing ionic strength of the buffer used to dissolve the lyophilised receptor.