The aim of this work is to investigate the binding affinity between the prokaryotic proteins-AHU-IHF proteins (AHU (AHU2, TR3, and AHU6) and IHF (IHF-WT and IHF-βE44A))-and DNAs (DNA, H'-DNA, and H'44A-DNA) by using the steered molecular dynamics (SMD) simulation and the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) method. The gained results show that although the fluctuation of the pulling force yielded the change of the pulling work, the higher pulling work of the AHU/DNA complexes in comparison to those of the IHF/DNA complexes is not only dependent on the pulling force but also controlled by the change of the trajectory in SMD simulation process. In this study, the pulling work profile not only described the pulling pathway of the complexes but also reflected the hindered process of DNAs when AHU-IHF proteins come out from the binding pocket of DNAs. Additionally, the binding free energy (estimated by the MM-PBSA method) is more confident in giving a true effect to the experimental results in comparison to the pulling force and the pulling work values. These results have also shown a fact that the AHU/DNA complexes were more stable than the IHF/DNA complexes.
Keywords: AHU proteins (AHU2, TR3, and AHU6); AHU-IHF proteins, DNAs (DNA, H′-DNA, and H′44A-DNA); AHU/DNA complexes; IHF proteins (IHF-WT and IHF-βE44A); IHF/DNA complexes; MM-PBSA method; SMD.