Equilibrium hormone binding to human estrogen receptors in highly diluted cell extracts is non-cooperative and has a Kd of approximately 10 pM.
It is generally accepted that the Kd for hormone binding to estrogen receptors in extracts ranges between 0.1-1 nM and that binding displays positive cooperativity due to formation of homodimers. After carefully optimizing assay procedures, to diminish ligand depletion phenomena and to fully control recoveries, we find a single class of non-interacting high affinity hormone binding sites with a Kd of approx. 10 pM. Ligand depletion was avoided by decreasing receptor concentrations to 5-8 pM. We were therefore obliged to employ radioiodinated estradiol as a probe as the specific radioactivity of tritiated estradiol was too low to maintain the accuracy of the binding assay. Human estrogen receptor extracted from the MCF7 cell line and recombinantly produced (in yeast) wild-type human receptor have identical equilibrium hormone binding characteristics.
Salomonsson
M
M
KaroBio AB, Huddinge, Sweden.
Carlsson
B
B
Häggblad
J
J
D002474:Cell-Free System; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D011960:Receptors, Estrogen / Q000378:metabolism*; D011994:Recombinant Proteins; D014407:Tumor Cells, Cultured
D011960:Receptors, Estrogen; D011994:Recombinant Proteins; D004958:Estradiol