Zinc Finger Protein Binding to DNA: An Energy Perspective Using Molecular Dynamics Simulation and Free Energy Calculations on Mutants of both Zinc Finger Domains and their Specific

Abstract

Energy calculations based on MM/GBSA were employed to study various zinc finger protein motifs binding to DNA. Mutants of both the DNA bound to their specific amino acids were studied. Calculated energies gave evidence for a relationship between binding energy and affinity of zinc finger motifs to their sites on DNA. ΔG values were -15.82(12), -3.66(12) and ¬12.14(11.6) Kcal/mol for finger one, finger two and finger three respectively. The mutations in the DNA bases reduced the value of the negative energies of binding (maximum value for ΔΔG = 42Kcal/mol for F1 when GCG mutated to GGG, and ΔΔG = 22 Kcal/mol for F2, the loss in total energy of binding originated in the loss in electrostatic energies upon mutation(r= 0.98). The mutations in key amino acids in the zinc finger motif in positions - 1, 2, 3 and 6 showed reduced binding energies to DNA with correlation coefficients between total free energy and electrostatic was 0.99 and with Van der Waal was 0.93. Results agree with experimentally found selectivity which showed that Arginine in position -1 is specific to G, while Aspartic acid (D) in position 2 plays a complicated role in binding. There is a correlation between the MD calculated free energies of binding and those obtained experimentally for prepared zinc finger motifs bound to triplet bases in other reports (D J Segal, Dreier, Beerli, & Barbas, 1999) , our results may help in the design of zinc finger motifs based on the established recognition codes based on energies and contributing energies to the total energy.