11 beta-chloromethyl-[3H]estradiol-17 beta: a very high affinity, reversible ligand for the estrogen receptor.
It has been suggested that binding of 11 beta-chloromethyl estradiol (11 beta-CME2) to the estrogen receptor is irreversible, since its complex with receptor fails to undergo exchange with estradiol (E2). To investigate this behavior directly, 11 beta-CME2 was prepared in high specific activity, tritium-labeled form: The binding of [3H]11 beta-CME2 to the estrogen receptor from lamb and rat uterus and MCF-7 human breast cancer cells was shown to be fully reversible; the 11 beta-CME2 complex with receptor, as well as that of a structural analog 11 beta-ethyl estradiol, however, do not dissociate or exchange with [3H]E2 over a 22 h period at 25 degrees C. By competitive or direct binding assays, the affinity of 11 beta-CME2 for the estrogen receptor can be estimated to be as much as 10- to 30-fold higher than that of E2. The complexes of estrogen receptor from MCF-7 cells with [3H]11 beta-CME2 and [3H]E2 show identical velocity sedimentation profiles on sucrose gradients, under conditions when the receptor is either a monomer of a dimer. Because of its very high affinity and unusual dissociation kinetics, [3H]11 beta-CME2 should be a very useful ligand for studies of estrogen receptor dynamics and in the assay of estrogen receptor concentrations in tumors and tissues.
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School of Chemical Sciences, University of Illinois, Urbana 61801.
Carlson
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KE
Reiner
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GC
Katzenellenbogen
J A
JA
D000818:Animals; D001388:Aziridines / Q000378:metabolism; D001667:Binding, Competitive; D001943:Breast Neoplasms / Q000378:metabolism; D002460:Cell Line; D002499:Centrifugation, Density Gradient; D055598:Chemical Phenomena; D002621:Chemistry; D004126:Dimethylformamide / Q000494:pharmacology; D004958:Estradiol / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000378:metabolism; D045166:Estradiol Congeners; D005260:Female; D006801:Humans; D007659:Ketones / Q000378:metabolism; D007700:Kinetics; D051381:Rats; D011960:Receptors, Estrogen / Q000378:metabolism*; D012756:Sheep; D014599:Uterus / Q000378:metabolism
D001388:Aziridines; D045166:Estradiol Congeners; D007659:Ketones; D011960:Receptors, Estrogen; C052977:ketononestrol aziridine; D004958:Estradiol; C038957:11-beta-chloromethyl-estradiol; D004126:Dimethylformamide