Differences in the form of the salt-transformed estrogen receptor when bound by estrogen versus antiestrogen.
Our laboratory has previously reported that antiestrogen binding to molybdate-stabilized non-transformed estrogen receptor results in a larger form of the receptor in 0.3 M KCl when compared with estrogen bound receptor. Estradiol promoted the formation of monomers in the presence of 0.3 M KCl whereas antiestrogen appeared to promote dimer formation. We have extended these studies examining the rabbit uterine salt-transformed estrogen receptor partially purified by DEAE-cellulose chromatography. We previously demonstrated that estrogen receptor prepared in this way bound to different sites on partially deproteinized chromatin subfractions or reconstituted chromosomal protein/DNA fractions when the receptor was complexed with estrogen vs antiestrogen. Analysis of these receptor preparations indicated that DEAE-cellulose step-elution resulted in a peak fraction which sedimented as a single 5.9S peak in 5-20% sucrose density gradients containing 0.3 M KCl for receptor bound by the antiestrogens H1285 and trans-hydroxytamoxifen. However, receptor bound by estradiol sedimented as 4.5S. These receptor complexes bound DNA-cellulose indicating that these partially purified receptors were transformed. DEAE rechromatography or agarose gel filtration of the partially purified antiestrogen-receptor complexes resulted in significant dissociation of the larger complex into monomers. Incubations of 5.9S antiestrogen-receptor complexes with antibodies against nontransformed steroid receptor-associated proteins (the 59 and 90 kDa proteins) did not result in the interaction of this larger antiestrogen-receptor complex with these antibodies (obtained from L. E. Faber and D. O. Toft, respectively). Our results support the concept that antiestrogen binding induces a different receptor conformation which could affect monomer-dimer equilibrium, thus rendering the antiestrogen-receptor complex incapable of inducing complete estrogenic responses in target tissues.
Ruh
M F
MF
Department of Physiology, St Louis University School of Medicine, MO 63104.
Turner
J W
JW
Paulson
C M
CM
Ruh
T S
TS
D000818:Animals; D000906:Antibodies / Q000032:analysis; D002499:Centrifugation, Density Gradient; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D004958:Estradiol / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000494:pharmacology*; D005260:Female; D011189:Potassium Chloride / Q000494:pharmacology*; D011487:Protein Conformation; D011817:Rabbits; D011955:Receptors, Drug; D011960:Receptors, Estrogen / Q000737:chemistry / Q000187:drug effects* / Q000276:immunology; D014599:Uterus / Q000737:chemistry
D000906:Antibodies; D004965:Estrogen Antagonists; D011955:Receptors, Drug; D011960:Receptors, Estrogen; D004958:Estradiol; D011189:Potassium Chloride