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Long-Range Modulations of Electric Fields in Proteins
Citation key 178.2018.Biava
Author Biava, H. and Schreiber, T. and Katz, S. and Völler, J-S. and Stolarski, M. and Schulz, C. and Michael, N. and Budisa, N. and Kozuch, J. and Tillmann, U. and Hildebrandt, P.
Pages 8330-8342
Year 2018
DOI 10.1021/acs.jpcb.8b03870
Journal J. Phys. Chem. B
Volume B122 (35)
Abstract Electrostatic interactions are essential for controlling the protein structure and function. Whereas so far experimental and theoretical efforts focused on the effect of local electrostatics, this work aims at elucidating the long-range modulation of electric fields in proteins upon binding to charged surfaces. The study is based on cytochrome c (Cytc) variants carrying nitrile reporters for the vibrational Stark effect that are incorporated into the protein via genetic engineering and chemical modification. The Cytc variants were thoroughly characterized with respect to possible structural perturbations due to labeling. For the proteins in solution, the relative hydrogen bond occupancy and the calculated electric fields, both obtained from molecular dynamics (MD) simulations, and the experimental nitrile stretching frequencies were used to develop a relationship for separating hydrogen-bonding and non-hydrogen-bonding electric field effects. This relationship provides an excellent description for the stable Cytc variants in solution. For the proteins bound to Au electrodes coated with charged self-assembled monolayers (SAMs), the underlying MD simulations can only account for the electric field changes ΔEads due to the formation of the electrostatic SAM–Cytc complexes but not for the additional contribution, ΔEint, representing the consequences of the potential drops over the electrode/SAM/protein interfaces. Both ΔEads and ΔEint, determined at distances between 20 and 30 Å with respect to the SAM surface, are comparable in magnitude to the non-hydrogen-bonding electric field in the unbound protein. This long-range modulation of the internal electric field may be of functional relevance for proteins in complexes with partner proteins (ΔEads) and attached to membranes (ΔEads + ΔEint).
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