Assay Method Information

Assay Name:  Estrogen Receptor Coactivator Assay
Description:  It is a competition assay, where binding of a test compound to a complex comprised of (i) His6-ERα298-554 protein representing ERα ligand-binding domain, (ii) Tb-labeled His6 antibody, (iii) a fluorescein-labeled PGC1α coactivator peptide (EAEEPSLLKKLLLAPANTQ), and (iv) estradiol, results in a decrease of the TR-FRET signal due to dissociation of the coactivator peptide. His6-ERα298-554 proteins were expressed as WT or D538G or Y537S mutants in E. coli and purified by affinity chromatography. The assay works in a homogeneous mix-and-read format. In a typical experiment, a 4 μL mixture of 0.5 nM His6-ERα298-554, 0.5 nM Tb-labeled His6 antibody, 250 nM PGC1a peptide, and 3 nM estradiol in 100 mM potassium phosphate, pH 7.4, 0.01% Tween-20, 0.02% NaN3, 5 mM DTT, was added to 40 nL test compound in DMSO and incubated overnight at room temperature. The TR-FRET 520:495 nm emission ratio was calculated and used to determine the IC50 value from a dose response curve fit to the 4-parameter logistic equation. The antagonist activity with respect to estrogen receptors in this test is given by the concentration which inhibits 50% of the estrogen receptor activity (or IC50) in nM.
Affinity data for this assay
 

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