Purification of chick oviduct progesterone receptor apoprotein

The 8S progesterone receptor from chick oviduct has been partially purified (500-fold) as the apoprotein lacking hormone. The procedure employs polyethylene glycol precipitation, phosphocellulose, DNA cellulose, DEAE cellulose, hydroxylapatite and ethyl agarose column chromatography. As shown for the native cytosolic receptor, the purified apoprotein can be dissociated into A and B subunits. Qualitative and quantitative analysis of subunit structure shows no difference between purified and cytosolic native progesterone receptor. The A subunit dissociated from the purified receptor maintains its DNA binding activity as shown by the “Western” protein blotting technique and sedimentation velocity analysis. Moreover, purified progesterone receptor has steroid binding specificity very close to the native material. The purified progesterone receptor is free of DNase and RNase contaminating activities and represents a useful tool for in vitro studies of hormone action.