title: Enthalpic factors override the polyelectrolyte effect in the binding of EGR1 transcription factor to DNA.
abstract: Protein-DNA interactions are highly dependent upon salt such that the binding affinity precipitously decreases with increasing salt concentration in a phenomenon termed as the polyelectrolyte effect. In this study, we provide evidence that the binding of early growth response (EGR) 1 transcription factor to DNA displays virtually zero dependence on ionic strength under physiological salt concentrations and that such feat is accomplished via favorable enthalpic contributions. Importantly, we unearth the molecular origin of such favorable enthalpy and attribute it to the ability of H382 residue to stabilize the EGR1-DNA interaction via both intermolecular hydrogen bonding and van der Waals contacts against the backdrop of salt. Consistent with this notion, the substitution of H382 residue with other amino acids faithfully restores salt-dependent binding of EGR1 to DNA in a canonical fashion. Remarkably, H382 is highly conserved across other members of the EGR family, implying that changes in bulk salt concentration are unlikely to play a significant role in modulating protein-DNA interactions central to this family of transcription factors. Taken together, our study reports the first example of a eukaryotic protein-DNA interaction capable of overriding the polyelectrolyte effect.
authors.affiliation: Department of Biochemistry and 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: Caleb B
authors.initials: CB
authors.lastname: McDonald
authors.forename: Amjad
authors.initials: A
authors.lastname: Farooq
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D004247:DNA / Q000737:chemistry*; D004268:DNA-Binding Proteins / Q000737:chemistry*; D051766:Early Growth Response Protein 1 / Q000737:chemistry* / Q000378:metabolism; D006860:Hydrogen Bonding; D011485:Protein Binding; D011487:Protein Conformation; D012492:Salts / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D012492:Salts; D004247:DNA
keywords: Protein-DNA thermodynamics; hydrogen bonding; polyelectrolyte effect; salt tolerance; van der Waals contacts