ABSTRACT
In this chapter, the authors review eminent scientists work on in vitro regulation of hormone binding to the receptor by receptor phosphorylation/dephosphorylation. They argue that estradiol receptor is phosphorylated on tyrosine in whole uterus and interacts with high affinity with antiphosphotyrosine antibodies coupled to Sepharose. The work from eminent scientists laboratory shows the presence of a tyrosine kinase which confers hormone binding to the estradiol receptor in mouse and calf uteri. Removal of nuclei and incubation of cytosol with adenosine triphosphate (ATP) completely restores the loss of hormone binding. The phosphatase assayed as hormone-binding inactivating activity has been found in nuclei of mouse uterus and mammary gland. That dephosphorylation by the receptor-phosphatase was responsible for the inactivation of the receptor present in the supernatant was demonstrated by the reactivation of the inactivated receptor by incubation of the anti-P-tyr-Sepharose supernatant with ATP.
