1. Direct Evidence Revealing Structural Elements Essential for the High Binding Ability of Bisphenol A to Human Estrogen-Related Receptor-γ.
- Author
-
Okada, Hiroyuki, Tokunaga, Takatoshi, Xiaohui Liu, Takayanagi, Sayaka, Matsushima, Ayami, and Shimohigashi, Yasuyuki
- Subjects
- *
BISPHENOL A , *ENDOCRINE disruptors , *METABOLITES , *ESTROGEN receptors , *PHENOLS in the body , *LIGAND binding (Biochemistry) , *CHEMICAL kinetics , *MOLECULAR structure , *LUCIFERASES , *METHYL groups - Abstract
BACKGROUND: Various 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. OBJECTIVES: In 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. METHODS: We 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 essentials required for the binding of BPA to ERR-γ, we found that only one of the two phenol-hydroxyl groups was essential for the full binding. The maximal activity was attained when one of the methyl groups was removed. All of the potent BPA derivatives retained a high constitutive basal activity of ERR-γ in the luciferase reporter gene assay and exhibited a distinct inhibitory activity against 4-OHT. CONCLUSION: These results indicate that the phenol derivatives are potent candidates for the endocrine disruptor that binds to ERR-γ. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF