Binding of Xenoestrogens and Phytoestrogens to Estrogen Receptor beta of Japanese Quail (Coturnix japonica)

摘要

In order to examine the binding affinity of various estrogenic compounds to estrogen receptor beta (ER beta), the cDNA encoding the hinge domain, the ligand-binding domain, and the C-terminal domain of quail ER beta was constructed and transfected into competent Escherichia coli. The binding assay performed using the supernatant of the cell lysates showed that bacterially-expressed ER beta has one single class of binding site for estradiol-17 beta with a dissociation constant of 4.90 + 0.16 X 10~(-9)M. The competition studies indicated that the relative binding affinities for the synthetic estrogens, diethylstilbestrol and ethinyl estradiol, are very high, while those for the xenoestrogens, bisphenol A and nonylphenol, are very low. Coumestrol, known as one of phytoestrogens, can compete with estradiol-17 beta with higher binding affinity for ER beta than ER alpha.