Structural and thermodynamic consequences of the replacement of zinc with environmental metals on estrogen receptor α-DNA interactions.
Estrogen receptor α (ERα) acts as a transcription factor by virtue of the ability of its DNA-binding (DB) domain, comprised of a tandem pair of zinc fingers, to recognize the estrogen response element within the promoters of target genes. Herein, using an array of biophysical methods, we probe the structural consequences of the replacement of zinc within the DB domain of ERα with various environmental metals and their effects on the thermodynamics of binding to DNA. Our data reveal that whereas the DB domain reconstituted with divalent ions of zinc, cadmium, mercury, and cobalt binds to DNA with affinities in the nanomolar range, divalent ions of barium, copper, iron, lead, manganese, nickel, and tin are unable to regenerate DB domain with DNA-binding potential, although they can compete with zinc for coordinating the cysteine ligands within the zinc fingers. We also show that the metal-free DB domain is a homodimer in solution and that the binding of various metals only results in subtle secondary and tertiary structural changes, implying that metal coordination may only be essential for binding to DNA. Collectively, our findings provide mechanistic insights into how environmental metals may modulate the physiological function of a key nuclear receptor involved in mediating a plethora of cellular functions central to human health and disease.
Department of Biochemistry and Molecular Biology and USylvester Braman Family Breast Cancer Institute, Leonard Miller School of Medicine, University of Miami, Miami, FL 33136, USA.
Brian J
BJ
Deegan
Anna M
AM
Bona
Vikas
V
Bhat
David C
DC
Mikles
Caleb B
CB
McDonald
Kenneth L
KL
Seldeen
Amjad
A
Farooq
D002151:Calorimetry; D002942:Circular Dichroism; D003545:Cysteine / Q000737:chemistry; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004785:Environmental Pollutants / Q000737:chemistry*; D047628:Estrogen Receptor alpha / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008024:Ligands; D008670:Metals / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D013816:Thermodynamics; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism; D016335:Zinc Fingers
D004785:Environmental Pollutants; D047628:Estrogen Receptor alpha; D008024:Ligands; D008670:Metals; D004247:DNA; D015032:Zinc; D003545:Cysteine