Direct Evidence Revealing Structural Elements Essential for the High Binding Ability of Bisphenol A to Human Estrogen-Related Receptor-γ

BackgroundVarious lines of evidence have shown that bisphenol A [BPA; HO-C6H4-C(CH3)2-C6H4-OH] acts as an endocrine disruptor when present in very low doses. We have recently demonstrated that BPA binds strongly to human estrogen-related receptor-γ (ERR-γ ) in a binding assay using [3H]4-hydroxytamoxifen ([3H]4-OHT). We also demonstrated that BPA inhibits the deactivation activity of 4-OHT.ObjectivesIn the present study, we intended to obtain direct evidence that BPA interacts with ERR-γ as a strong binder, and also to clarify the structural requirements of BPA for its binding to ERR-γ.MethodsWe examined [3H]BPA in the saturation binding assay using the ligand binding domain of ERR-γ and analyzed the result using Scatchard plot analysis. A number of BPA derivatives were tested in the competitive binding assay using [3H]BPA as a tracer and in the luciferase reporter gene assay.Results[3H]BPA showed a KD of 5.50 nM at a Bmax of 14.4 nmol/mg. When we examined BPA derivatives to evaluate the structural essent...