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. Copyright © 2014 John Wiley & Sons, Ltd.
Binding of early growth response (EGR) 1 transcription factor to DNA displays virtually zero dependence on physiological concentrations of salt. Such feat is accomplished via favorable enthalpic contributions solely because of H382. Importantly, H382 engages in key intermolecular hydrogen bonding and van der Waals contacts with DNA. Consistent with this notion, replacement of H382 with other amino acids abolishes salt‐dependent binding of EGR1 to DNA. Of particular note is the observation that the H382 is predominantly conserved in other members of the EGR family.
