title: Direct evidence revealing structural elements essential for the high binding ability of bisphenol A to human estrogen-related receptor-gamma.
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-gamma (ERR-gamma ) in a binding assay using [3H]4-hydroxytamoxifen ([3H]4-OHT). We also demonstrated that BPA inhibits the deactivation activity of 4-OHT.
  
  
  OBJECTIVE
  In the present study, we intended to obtain direct evidence that BPA interacts with ERR-gamma as a strong binder, and also to clarify the structural requirements of BPA for its binding to ERR-gamma.
  
  
  METHODS
  We examined [3H]BPA in the saturation binding assay using the ligand binding domain of ERR-gamma 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-gamma , 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-gamma in the luciferase reporter gene assay and exhibited a distinct inhibitory activity against 4-OHT.
  
  
  CONCLUSIONS
  These results indicate that the phenol derivatives are potent candidates for the endocrine disruptor that binds to ERR-gamma.
authors.affiliation: Laboratory of Structure-Function Biochemistry, Department of Chemistry, The Research-Education Centre of Risk Science, Faculty and Graduate School of Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Okada
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Tokunaga
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Liu
authors.forename: Sayaka
authors.initials: S
authors.lastname: Takayanagi
authors.forename: Ayami
authors.initials: A
authors.lastname: Matsushima
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Shimohigashi
mesh_terms: D001559:Benzhydryl Compounds; D001667:Binding, Competitive; D052244:Endocrine Disruptors / Q000737:chemistry / Q000378:metabolism*; D004968:Estrogens, Non-Steroidal / Q000737:chemistry / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D010636:Phenols / Q000737:chemistry / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000378:metabolism*; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000378:metabolism; D000098826:Bisphenol A Compounds
chemical_list: D001559:Benzhydryl Compounds; D052244:Endocrine Disruptors; D004968:Estrogens, Non-Steroidal; D010636:Phenols; D018160:Receptors, Cytoplasmic and Nuclear; D011960:Receptors, Estrogen; D013629:Tamoxifen; C490917:ESRRG protein, human; C016601:afimoxifene; C006780:bisphenol A; D000098826:Bisphenol A Compounds