A systematic approach has been taken in the development of photoaffinity labeling agents for the uterine estrogen receptor. Several derivatives of estradiol and the nonsteroidal estrogen, hexestrol, containing photoreactive diazocarbonyl or azide functions have been synthesized. The receptor binding affinities of these compounds and their capacity to photointeract with the estrogen binding site (inactivate) can be assayed indirectly by competition assays, and the compounds that showed both reasonably high binding affinities and inactivation efficiencies have been prepared in high specific activity, tritium-labeled form. Direct binding measurements with these derivatives, in unpurified rat uterine receptor preparations, show that these compounds bind to the receptor, but they also show considerable binding to nonreceptor proteins. Irradiation of these derivatives in rat uterine cytosol preparations results in incorporation of large amounts of radioactivity into protein in a covalent fashion, so that labeling of the estrogen binding site cannot be demonstrated. However, electrophoretic analysis of partially-purified estrogen receptor preparations from lamb uterus indicates that the estrogen receptor is being covalently labeled by one photoreactive derivative, hexestrol azide. The behavior of the labeled species is consistent with that of the estrogen receptor, and the efficiency of labeling corresponds to that expected from prior inactivation studies.
|Original language||English (US)|
|Number of pages||5|
|State||Published - 1978|
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