A comparison of 11 beta-chloromethylestradiol and tamoxifen aziridine as affinity labeling reagents for estrogen receptors.
The tritium-labeled from of 11 beta-chloromethylestradiol was prepared by metal hydride reduction of the 17-keto derivative. Affinity labeling experiments were carried out using [3H] 11 beta-chloromethylestradiol and [3H]tamoxifen aziridine with estrogen receptor from crude, calf uterine cytosol and partially purified (heparin-sepharose chromatography) preparations. Both compounds formed highly stable receptor complexes. Estrogen specific, covalent binding, however, was indicated only for [3H]tamoxifen aziridine. An equilibrium dissociation constant of 2.8 x 10(-10) M was determined for the receptor-[3H] 11 beta-chloromethylestradiol interaction. Measurement of hormone dissociation kinetics at 30 degrees C revealed a slow, single phase dissociation of 11 beta-chloromethylestradiol from the receptor (dissociation rate constant, 1.3 x 10(-3) min-1). This contrasted with the normal biphasic dissociation pattern of estradiol in which the dissociation rate constant for the slower component was 16.7 x 10(-3) min-1. The results indicate that 11 beta-chloromethylestradiol readily converts the estrogen receptor to a high affinity binding form and suggest that the radiolabeled hormone may prove useful for studies of estrogen action.
Ratajczak
T
T
Department of Obstetrics and Gynecology, University of Western Australia, King Edward Memorial Hospital for Women, Subiaco.
Atrache
V
V
Antes
P
P
Comber
M
M
Hähnel
R
R
D000345:Affinity Labels / Q000378:metabolism*; D002021:Buffers; D002499:Centrifugation, Density Gradient; D003600:Cytosol; D004591:Electrophoresis, Polyacrylamide Gel; D004958:Estradiol / Q000031:analogs & derivatives* / Q000378:metabolism; D011960:Receptors, Estrogen / Q000378:metabolism*; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000378:metabolism
D000345:Affinity Labels; D002021:Buffers; D011960:Receptors, Estrogen; D013629:Tamoxifen; D004958:Estradiol; C038957:11-beta-chloromethyl-estradiol; C031859:tamoxifen aziridine