title: pH modulates the binding of early growth response protein 1 transcription factor to DNA.
abstract: The transcription factor early growth response protein (EGR)1 orchestrates a plethora of signaling cascades involved in cellular homeostasis, and its downregulation has been implicated in the development of prostate cancer. Herein, using a battery of biophysical tools, we show that the binding of EGR1 to DNA is tightly regulated by solution pH. Importantly, the binding affinity undergoes an enhancement of more than an order of magnitude with an increase in pH from 5 to 8, implying that the deprotonation of an ionizable residue accounts for such behavior. This ionizable residue is identified as His382 by virtue of the fact that its replacement by nonionizable residues abolishes the pH dependence of the binding of EGR1 to DNA. Notably, His382 inserts into the major groove of DNA, and stabilizes the EGR1-DNA interaction via both hydrogen bonding and van der Waals contacts. Remarkably, His382 is mainly conserved across other members of the EGR family, implying that histidine protonation-deprotonation may serve as a molecular switch for modulating the protein-DNA interactions that are central to this family of transcription factors. Collectively, our findings reveal an unexpected but a key step in the molecular recognition of the EGR family of transcription factors, and suggest that they may act as sensors of pH within the intracellular environment.
authors.affiliation: Department of Biochemistry & Molecular Biology, Leonard Miller School of Medicine, University of Miami, Miami, FL 33136, USA.
authors.forename: David C
authors.initials: DC
authors.lastname: Mikles
authors.forename: Vikas
authors.initials: V
authors.lastname: Bhat
authors.forename: Brett J
authors.initials: BJ
authors.lastname: Schuchardt
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Deegan
authors.forename: Kenneth L
authors.initials: KL
authors.lastname: Seldeen
authors.forename: Caleb B
authors.initials: CB
authors.lastname: McDonald
authors.forename: Amjad
authors.initials: A
authors.lastname: Farooq
mesh_terms: D000595:Amino Acid Sequence; D004247:DNA / Q000737:chemistry*; D051766:Early Growth Response Protein 1 / Q000737:chemistry*; D006639:Histidine / Q000737:chemistry; D006801:Humans; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D055550:Protein Stability; D017433:Protein Structure, Secondary; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D006639:Histidine; D004247:DNA
keywords: histidine protonation; intracellular pH; protein dynamics; protein-DNA thermodynamics; zinc fingers