ESTROGEN AFFINITY CROSS-LINKING TO TYROSINASE-LIKE IMMUNOREACTIVE PROTEINS OF RAT UTERINE NUCLEAR EXTRACTS

We have previously described tyrosinase-like proteins of rat uterine n uclear extracts with type II estrogen binding characteristics. In this paper we have been able to affinity label these polypeptides with rad io-iodinated estradiol. The major label at similar to 33-38 kDa comigr ates with a similar to 36 kDa tyrosinase immunoreactive band assessed by autoradiograms and Western blots following electrophoresis. A minor label was also detected at similar to 45 kDa. The label is attenuated by excess quercetin hence these proteins are believed to represent pu tative type II estrogen binding sites that bind this bioflavonoid. The se estrogen binding proteins are distinct from the estrogen receptor a s judged by immunoblotting. The affinity crosslinking will be a useful approach in the purification of tyrosinase like proteins.