scholarly journals Continuous B- to A- Transition in Protein-DNA Binding - How Well Is It Described by Current AMBER Force Fields?

2022 ◽  
Author(s):  
Petr Jurecka ◽  
Marie Zgarbova ◽  
Filip Cerny ◽  
Jan Salomon
Keyword(s):  
Force Fields ◽  
Md Simulations ◽  
Binding Motif ◽  
Dna Complexes ◽  
Continuous Transition ◽  
Correct Sequence ◽  
Protein Dna Interactions ◽  
Intermediate States ◽  
Amber Force Fields ◽  
Dna Complex

When DNA interacts with a protein, its structure often undergoes significant conformational adaptation. Perhaps the most common is the transition from canonical B-DNA towards the A-DNA form, which is not a two-state, but rather a continuous transition. The A- and B- forms differ mainly in sugar pucker P (north/south) and glycosidic torsion χ (high-anti/anti). The combination of A-like P and B-like χ (and vice versa) represents the nature of the intermediate states lying between the pure A- and B- forms. In this work, we study how the A/B equilibrium and in particular the A/B intermediate states, which are known to be over-represented at protein-DNA interfaces, are modeled by current AMBER force fields. Eight protein-DNA complexes and their naked (unbound) DNAs were simulated with OL15 and bsc1 force fields as well as an experimental combination OL15χOL3. We found that while the geometries of the A-like intermediate states in the molecular dynamics (MD) simulations agree well with the native X-ray geometries found in the protein-DNA complexes, their populations (stabilities) are significantly underestimated. Different force fields predict different propensities for A-like states growing in the order OL15 < bsc1 < OL15χOL3, but the overall populations of the A-like form are too low in all of them. Interestingly, the force fields seem to predict the correct sequence-dependent A-form propensity, as they predict larger populations of the A-like form in naked (unbound) DNA in those steps that acquire A-like conformations in protein-DNA complexes. The instability of A-like geometries in current force fields may significantly alter the geometry of the simulated protein-DNA complex, destabilize the binding motif, and reduce the binding energy, suggesting that refinement is needed to improve description of protein-DNA interactions in AMBER force fields.

scholarly journals Z-DNA as a Touchstone for Additive Empirical Force Fields and a Refinement of the Alpha/Gamma DNA torsions for AMBER

2021 ◽  
Author(s):  
Marie Zgarbova ◽  
Jiri Sponer ◽  
Petr Jurecka
Keyword(s):  
Force Fields ◽  
Difficult Case ◽  
Additive Effects ◽  
Correct Description ◽  
Dna Complexes ◽  
Dna Motifs ◽  
Z Dna ◽  
Living Organisms ◽  
The Stability ◽  
Amber Force Fields

Although current AMBER force fields are relatively accurate for canonical B-DNA, many non-canonical structures are still described incorrectly. As non-canonical motifs are attracting increasing attention due to the role they play in living organisms, further improvement is desirable. Here, we have chosen Z-DNA molecule, can be considered a touchstone of the universality of empirical force fields, since the non-canonical α and γ backbone conformations native to Z-DNA are also found in protein-DNA complexes, i-motif DNA and other non-canonical DNAs. We show that spurious α/γ conformations occurring in simulations with current AMBER force fields, OL15 and bsc1, are largely due to inaccurate α/γ parameterization. Moreover, stabilization of native Z-DNA substates involving γ = trans conformations appears to be in conflict with the correct description of the canonical B-DNA structure. Because the balance of the native and spurious conformations is influenced by non-additive effects, this is a difficult case for an additive dihedral energy scheme such as AMBER. We propose new α/γ parameters, denoted OL21, and show that they improve the stability of native α/γ Z-DNA substates while keeping the canonical DNA description virtually unchanged, and thus represent a reasonable compromise within the additive force field framework. Although further extensive testing is needed, the new modification appears to be a promising step towards a more reliable description of non-canonical DNA motifs and provides the best performance for Z-DNA molecules among current AMBER force fields.

CONFORMATIONAL DYNAMICS OF HIV-1 PROTEASE: A COMPARATIVE MOLECULAR DYNAMICS SIMULATION STUDY WITH MULTIPLE AMBER FORCE FIELDS

2012 ◽  
Vol 10 (06) ◽  
pp. 1250018 ◽  
Author(s):  
BISWA RANJAN MEHER ◽  
MATTAPARTHI VENKATA SATISH KUMAR ◽  
SMRITI SHARMA ◽  
PRADIPTA BANDYOPADHYAY
Keyword(s):  
Force Field ◽  
Active Site ◽  
Force Fields ◽  
Conformational Dynamics ◽  
Md Simulations ◽  
Order Parameters ◽  
Dynamics Simulation ◽  
Active Site Cavity ◽  
Amber Force Fields ◽  
Hiv 1

Flap dynamics of HIV-1 protease (HIV-pr) controls the entry of inhibitors and substrates to the active site. Dynamical models from previous simulations are not all consistent with each other and not all are supported by the NMR results. In the present work, the effect of force field on the dynamics of HIV-pr is investigated by MD simulations using three AMBER force fields ff99, ff99SB, and ff03. The generalized order parameters for amide backbone are calculated from the three force fields and compared with the NMR S2 values. We found that the ff99SB and ff03 force field calculated order parameters agree reasonably well with the NMR S2 values, whereas ff99 calculated values deviate most from the NMR order parameters. Stereochemical geometry of protein models from each force field also agrees well with the remarks from NMR S2 values. However, between ff99SB and ff03, there are several differences, most notably in the loop regions. It is found that these loops are, in general, more flexible in the ff03 force field. This results in a larger active site cavity in the simulation with the ff03 force field. The effect of this difference in computer-aided drug design against flexible receptors is discussed.

scholarly journals Predicting transcription factor specificity with all-atom models

2008 ◽  
Vol 36 (19) ◽  
pp. 6209-6217 ◽  
Author(s):  
Sahand J. Rahi ◽  
Peter Virnau ◽  
Leonid A. Mirny ◽  
Mehran Kardar
Keyword(s):  
Transcription Factor ◽  
Computational Prediction ◽  
Systematic Evaluation ◽  
Dna Complexes ◽  
Atomistic Models ◽  
Protein Dna Interactions ◽  
Factor Specificity ◽  
Ab Initio Approach ◽  
Dna Complex ◽  
Operator Site

Abstract The binding of a transcription factor (TF) to a DNA operator site can initiate or repress the expression of a gene. Computational prediction of sites recognized by a TF has traditionally relied upon knowledge of several cognate sites, rather than an ab initio approach. Here, we examine the possibility of using structure-based energy calculations that require no knowledge of bound sites but rather start with the structure of a protein–DNA complex. We study the PurR Escherichia coli TF, and explore to which extent atomistic models of protein–DNA complexes can be used to distinguish between cognate and noncognate DNA sites. Particular emphasis is placed on systematic evaluation of this approach by comparing its performance with bioinformatic methods, by testing it against random decoys and sites of homologous TFs. We also examine a set of experimental mutations in both DNA and the protein. Using our explicit estimates of energy, we show that the specificity for PurR is dominated by direct protein–DNA interactions, and weakly influenced by bending of DNA.

Assessing AMBER force fields for protein folding in an implicit solvent

2018 ◽  
Vol 20 (10) ◽  
pp. 7206-7216 ◽  
Author(s):  
Qiang Shao ◽  
Weiliang Zhu
Keyword(s):  
Protein Folding ◽  
Force Fields ◽  
Md Simulations ◽  
Implicit Solvent ◽  
Amber Force Fields ◽  
Folding Thermodynamics

MD simulations quantitatively assess the availability and limitation of six recently developed AMBER force fields in reproducing protein native structures and measuring folding thermodynamics under implicit solvent conditions.

Assessment of AMBER Force Fields for Simulations of ssDNA

2021 ◽  
Vol 17 (2) ◽  
pp. 1208-1217
Author(s):  
Thomas J. Oweida ◽  
Ho Shin Kim ◽  
Johnny M. Donald ◽  
Abhishek Singh ◽  
Yaroslava G. Yingling
Keyword(s):  
Force Fields ◽  
Amber Force Fields

scholarly journals High-resolution mining of the SARS-CoV-2 main protease conformational space: supercomputer-driven unsupervised adaptive sampling

2021 ◽  
Author(s):  
Théo Jaffrelot Inizan ◽  
Frédéric Célerse ◽  
Olivier Adjoua ◽  
Dina El Ahdab ◽  
Luc-Henri Jolly ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
High Resolution ◽  
Adaptive Sampling ◽  
Force Fields ◽  
Sampling Strategy ◽  
Md Simulations ◽  
Conformational Space ◽  
Many Body ◽  
Polarizable Force Fields ◽  
Main Protease

We provide an unsupervised adaptive sampling strategy capable of producing μs-timescale molecular dynamics (MD) simulations of large biosystems using many-body polarizable force fields (PFFs).

Microscopic understanding of the conformational features of a protein–DNA complex

2017 ◽  
Vol 19 (48) ◽  
pp. 32459-32472 ◽  
Author(s):  
Sandip Mondal ◽  
Kaushik Chakraborty ◽  
Sanjoy Bandyopadhyay
Keyword(s):  
Dna Interactions ◽  
P Protein ◽  
Protein Dna Interactions ◽  
Initiation Of Transcription ◽  
Dna Complex

Protein–DNA interactions play crucial roles in different stages of genetic activities, such as replication of genome, initiation of transcription,etc.

Thermodynamics of Helix formation in small peptides of varying lengthin vacuo, implicit solvent and explicit solvent: Comparison between AMBER force fields

2019 ◽  
Vol 18 (03) ◽  
pp. 1950015
Author(s):  
Zhaoxi Sun ◽  
Xiaohui Wang
Keyword(s):  
Amino Acids ◽  
Free Energy ◽  
Hydrogen Bonds ◽  
Force Fields ◽  
Implicit Solvent ◽  
Conformational Ensemble ◽  
Helix Formation ◽  
Solvent Models ◽  
Explicit Solvent ◽  
Amber Force Fields

Helix formation is of great significance in protein folding. The helix-forming tendencies of amino acids are accumulated along the sequence to determine the helix-forming tendency of peptides. Computer simulation can be used to model this process in atomic details and give structural insights. In the current work, we employ equilibrate-state free energy simulation to systematically study the folding/unfolding thermodynamics of a series of mutated peptides. Two AMBER force fields including AMBER99SB and AMBER14SB are compared. The new 14SB force field uses refitted torsion parameters compared with 99SB and they share the same atomic charge scheme. We find that in vacuo the helix formation is mutation dependent, which reflects the different helix propensities of different amino acids. In general, there are helix formers, helix indifferent groups and helix breakers. The helical structure becomes more favored when the length of the sequence becomes longer, which arises from the formation of additional backbone hydrogen bonds in the lengthened sequence. Therefore, the helix indifferent groups and helix breakers will become helix formers in long sequences. Also, protonation-dependent helix formation is observed for ionizable groups. In 14SB, the helical structures are more stable than in 99SB and differences can be observed in their grouping schemes, especially in the helix indifferent group. In solvents, all mutations are helix indifferent due to protein–solvent interactions. The decrease in the number of backbone hydrogen bonds is the same with the increase in the number of protein–water hydrogen bonds. The 14SB in explicit solvent is able to capture the free energy minima in the helical state while 14SB in implicit solvent, 99SB in explicit solvent and 99SB in implicit solvent cannot. The helix propensities calculated under 14SB agree with the corresponding experimental values, while the 99SB results obviously deviate from the references. Hence, implicit solvent models are unable to correctly describe the thermodynamics even for the simple helix formation in isolated peptides. Well-developed force fields and explicit solvents are needed to correctly describe the protein dynamics. Aside from the free energy, differences in conformational ensemble under different force fields in different solvent models are observed. The numbers of hydrogen bonds formed under different force fields agree and they are mostly determined by the solvent model.

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