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MolDock: a new technique for high-accuracy molecular docking.

In this article we introduce a molecular docking algorithm called MolDock. MolDock is based on a new heuristic search algorithm that combines differential evolution with a cavity prediction algorithm. The docking scoring function of MolDock is an extension of the piecewise linear potential (PLP) including new hydrogen bonding and electrostatic terms. To further improve docking accuracy, a re-ranking scoring function is introduced, which identifies the most promising docking solution from the solutions obtained by the docking algorithm. The docking accuracy of MolDock has been evaluated by docking flexible ligands to 77 protein targets. MolDock was able to identify the correct binding mode of 87% of the complexes. In comparison, the accuracy of Glide and Surflex is 82% and 75%, respectively. FlexX obtained 58% and GOLD 78% on subsets containing 76 and 55 cases, respectively.

Algorithms↗

MCDOCK: a Monte Carlo simulation approach to the molecular docking problem.

Prediction of the binding mode of a ligand (a drug molecule) to its macromolecular receptor, or molecular docking, is an important problem in rational drug design. We have developed a new docking method in which a non-conventional Monte Carlo (MC) simulation technique is employed. A computer program, MCDOCK, was developed to carry out the molecular docking operation automatically. The current version of the MCDOCK program (version 1.0) allows for the full flexibility of ligands in the docking calculations. The scoring function used in MCDOCK is the sum of the interaction energy between the ligand and its receptor, and the conformational energy of the ligand. To validate the MCDOCK method, 19 small ligands, the binding modes of which had been determined experimentally using X-ray diffraction, were docked into their receptor binding sites. To produce statistically significant results, 20 MCDOCK runs were performed for each protein-ligand complex. It was found that a significant percentage of these MCDOCK runs converge to the experimentally observed binding mode. The root-mean-square (rms) of all non-hydrogen atoms of the ligand between the predicted and experimental binding modes ranges from 0.25 to 1.84 A for these 19 cases. The computational time for each run on an SGI Indigo2/R10000 varies from less than 1 min to 15 min, depending upon the size and the flexibility of the ligands. Thus MCDOCK may be used to predict the precise binding mode of ligands in lead optimization and to discover novel lead compounds through structure-based database searching.

Binding Sites↗

Q-fit: a probabilistic method for docking molecular fragments by sampling low energy conformational space.

A new method is presented that docks molecular fragments to a rigid protein receptor. It uses a probabilistic procedure based on statistical thermodynamic principles to place ligand atom triplets at the lowest energy sites. The probabilistic method ranks receptor binding modes so that the lowest energy ones are sampled first. This allows constraints to be introduced to limit the depth of the search leading to a computationally efficient method of sampling low energy conformational space. This is combined with energy minimization of the initial fragment placement to arrive at a low energy conformation for the molecular fragment. Two different search methods are tested involving (i) geometric hashing and (ii) pose clustering methods. Ten molecular fragments were docked that have commonly been used to test docking methods. The success rate was 8/10 and 10/10 for generating a close solution ranked first using the two different sampling procedures. In general, all five of the top ranked solutions reproduce the observed binding mode, which increases confidence in the predictions. A set of ten molecular fragments that have previously been identified as problematic were docked. Success was achieved in 3/10 and 4/10 using the two different methods. Again there is a high level of agreement between the two methods and again in the successful cases the top ranked solutions are correct whilst in the case of the failures none are. The geometric hashing and pose clustering methods are fast averaging approximately 13 and approximately 11 s per placement respectively using conservative parameters. The results are very encouraging and will facilitate the process of finding novel small molecule lead compounds by virtual screening of chemical databases.

Algorithms↗

Based on network pharmacology, molecular docking, and validation experiments to investigate the active components and mechanisms of action of Tibetan Medog County Citrus medica L.: In antioxidant activity.

BACKGROUND: The antioxidant potential of citrus plants is closely related to their geographical origin, making it crucial to evaluate the natural antioxidant properties of Citrus medica L. (C. medica) from Medog County, Tibet. METHODS: This study systematically investigates the antioxidant mechanisms of C. medica using network pharmacology, molecular docking, and experimental assays. RESULTS: The antioxidant activity experiments showed that C. medica exhibits good bioactivity, and the fruit has better antioxidant activity than the leaves. Network pharmacology revealed 11 active components of C. medica with 1547 antioxidant-related targets. Key targets include TP53, IL6, AKT1, STAT3, and TNF. Gene ontology (GO) analysis identified 1419 biological process entries, 147 cellular component entries, and 306 molecular function entries. Kyoto Encyclopedia of Genes and Genomes analysis identified 212 antioxidant-related signaling pathways. The GO and Kyoto Encyclopedia of Genes and Genomes enrichment analyses showed that the targets are involved in cancer pathways, protein binding, enzyme binding, lipid metabolism, and atherosclerosis. Molecular docking demonstrated that the 11 active components of Medog C. medica exhibit binding energies with core targets TP53, IL6, AKT1, STAT3, and TNF generally less than -5 kcal·mol-1, indicating good affinity. CONCLUSION: This study identifies the excellent antioxidant activity of C. medica from multiple aspects and elucidates its potential antioxidant mechanisms, providing a theoretical basis for the development and application of C. medica as an antioxidant functional additive.

Molecular Docking Simulation↗

Integrated network pharmacology, molecular docking, and experimental validation to reveal the potential mechanism of Ginsenoside Rg1 on chronic obstructive pulmonary disease.

Ginsenoside Rg1 (GS Rg1), a natural flavonoid exhibiting anti-inflammatory and antioxidant properties, holds significant potential for treatment chronic obstructive pulmonary disease (COPD). Nevertheless, the precise mechanisms underlying its therapeutic effects remain to be fully elucidated. This study aimed to explore the role and potential mechanism of GS Rg1 in the treatment of COPD using network pharmacology, molecular docking, and experimental validation.Targets related to GS Rg1 and COPD were screened from public databases, and the potential common targets were then imported into the STRING database to construct a protein-protein interaction (PPI) network. Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis were performed to identify key signaling pathways. Molecular docking was employed to predict the binding interactions between GS Rg1 and core targets. A BEAS-2B cell model induced by lipopolysaccharide(LPS) and cigarette smoke extract(CSE) was used to explore the protective mechanisms of GS Rg1. Western blot analysis was conducted to validate the critical targets and pathways involved in the anti-COPD effects of GS Rg1. Network pharmacology analysis revealed 105 common targets between GS Rg1 and COPD. The EGFR/PI3K/AKT and EGFR/STAT3 signaling pathways were selected for further validation. GS Rg1 was demonstrated to effectively inhibit inflammation and mucus hypersecretion in vitro models of COPD. Western blot results showed that GS Rg1 treatment significantly downregulated the expression of proteins involved in the EGFR/PI3K/AKT and EGFR/STAT3 signaling pathway, consistent with the network pharmacology findings. CSE/LPS exposure induces inflammation and oxidative stress in COPD by disrupting the EGFR/PI3K/AKT and EGFR/STAT3 signaling pathways, and GS Rg1 significantly alleviates these effects, which may be partially through regulating the EGFR/PI3K/AKT and EGFR/STAT3 signaling pathway.

Ginsenosides↗

Prediction of HIV-1 integrase/viral DNA interactions in the catalytic domain by fast molecular docking.

This study details the separate analyses of binding specificity of HIV-1 integrase (IN) and viral B-DNA forms through ligand-receptor docking studies by means of a fast molecular docking method. The application of solvated electrostatics with the University of Houston Brownian Dynamics Program (UHBD) and configurational sampling by the Daughter of Turnip (DOT) docking program resulted in the computation of energies of more than 113 billion configurations for each ligand-receptor docking study, a procedure considered computationally intractable a few years ago. A specific binding pattern of viral DNA to the IN catalytic domain region has been predicted as a result of these calculations. In a representative docked configuration, we observe the 3'-hydroxyl of the conserved deoxyadenosine to be close to one of the two divalent metal ions that are necessary for catalysis. A superimposition of our energy-minimized docked complex on representative structures from a molecular dynamics (MD) simulation of a crystallographically resolved IN/inhibitor complex revealed an overlap of viral DNA with the inhibitor, indicating that the bound inhibitor might operate by blocking substrate binding. The DOT docking calculation also identified a second, adjacent DNA-binding site, which we believe is the nonspecific host DNA binding site. The binding pattern predicted by DOT complements previous electrostatics, MD simulation, photo-cross-linking, and mutagenesis studies and also provides a further refinement of the IN/viral DNA binding interaction as a basis for new structure-based design efforts.

Catalytic Domain↗

FlexE: efficient molecular docking considering protein structure variations.

Side-chain or even backbone adjustments upon docking of different ligands to the same protein structure, a phenomenon known as induced fit, are frequently observed. Sometimes point mutations within the active site influence the ligand binding of proteins. Furthermore, for homology derived protein structures there are often ambiguities in side-chain placement and uncertainties in loop modeling which may be critical for docking applications. Nevertheless, only very few molecular docking approaches have taken into account such variations in protein structures. We present the new software tool FlexE which addresses the problem of protein structure variations during docking calculations. FlexE can dock flexible ligands into an ensemble of protein structures which represents the flexibility, point mutations, or alternative models of a protein. The FlexE approach is based on a united protein description generated from the superimposed structures of the ensemble. For varying parts of the protein, discrete alternative conformations are explicitly taken into account, which can be combinatorially joined to create new valid protein structures.FlexE was evaluated using ten protein structure ensembles containing 105 crystal structures from the PDB and one modeled structure with 60 ligands in total. For 50 ligands (83 %) FlexE finds a placement with an RMSD to the crystal structure below 2.0 A. In all cases our results are of similar quality to the best solution obtained by sequentially docking the ligands into all protein structures (cross docking). In most cases the computing time is significantly lower than the accumulated run times for the single structures. FlexE takes about five and a half minutes on average for placing one ligand into the united protein description on a common workstation. The example of the aldose reductase demonstrates the necessity of considering protein structure variations for docking calculations. We docked three potent inhibitors into four protein structures with substantial conformational changes within the active site. Using only one rigid protein structure for screening would have missed potential inhibitors whereas all inhibitors can be docked taking all protein structures into account.

Aldehyde Reductase↗

DOCK 4.0: search strategies for automated molecular docking of flexible molecule databases.

In this paper we describe the search strategies developed for docking flexible molecules to macomolecular sites that are incorporated into the widely distributed DOCK software, version 4.0. The search strategies include incremental construction and random conformation search and utilize the existing Coulombic and Lennard-Jones grid-based scoring function. The incremental construction strategy is tested with a panel of 15 crystallographic testcases, created from 12 unique complexes whose ligands vary in size and flexibility. For all testcases, at least one docked position is generated within 2 A of the crystallographic position. For 7 of 15 testcases, the top scoring position is also within 2 A of the crystallographic position. The algorithm is fast enough to successfully dock a few testcases within seconds and most within 100 s. The incremental construction and the random search strategy are evaluated as database docking techniques with a database of 51 molecules docked to two of the crystallographic testcases. Incremental construction outperforms random search and is fast enough to reliably rank the database of compounds within 15 s per molecule on an SGI R10000 cpu.

Algorithms↗

Modelling the structure of latexin-carboxypeptidase A complex based on chemical cross-linking and molecular docking.

We have determined the three-dimensional structure of the protein complex between latexin and carboxypeptidase A using a combination of chemical cross-linking, mass spectrometry and molecular docking. The locations of three intermolecular cross-links were identified using mass spectrometry and these constraints were used in combination with a speed-optimised docking algorithm allowing us to evaluate more than 3 x 10(11) possible conformations. While cross-links represent only limited structural constraints, the combination of only three experimental cross-links with very basic molecular docking was sufficient to determine the complex structure. The crystal structure of the complex between latexin and carboxypeptidase A4 determined recently allowed us to assess the success of this structure determination approach. Our structure was shown to be within 4 A r.m.s. deviation of Calpha atoms of the crystal structure. The study demonstrates that cross-linking in combination with mass spectrometry can lead to efficient and accurate structural modelling of protein complexes.

Algorithms↗

Towards discovering dual functional inhibitors against both wild type and K103N mutant HIV-1 reverse transcriptases: molecular docking and QSAR studies on 4,1-benzoxazepinone analogues.

To find useful information for discovering dual functional inhibitors against both wild type (WT) and K103N mutant reverse transcriptases (RTs) of HIV-1, molecular docking and 3D-QSAR approaches were applied to a set of twenty-five 4,1-benzoxazepinone analogues of efavirenz (SUSTIVA), some of them are active against the two RTs. 3D-QSAR models were constructed, based on their binding conformations determined by molecular docking, with r(2)(cv) values ranging from 0.656 to 0.834 for CoMFA and CoMSIA, respectively. The models were then validated to be highly predictive and extrapolative by inhibitors in two test sets with different molecular skeletons. Furthermore, CoMFA models were found to be well matched with the binding sites of both WT and K103N RTs. Finally, a reasonable pharmacophore model of 4,1-benzoxazepinones were established. The application of the model not only successfully differentiated the experimentally determined inhibitors from non-inhibitors, but also discovered two potent inhibitors from the compound database SPECS. On the basis of both the 3D-QSAR and pharmacophore models, new clues for discovering and designing potent dual functional drug leads against HIV-1 were proposed: (i) adopting positively charged aliphatic group at the cis-substituent of C3; (ii) reducing the electronic density at the position of O4; (iii) positioning a small branched aliphatic group at position of C5; (iv) using the negatively charged bulky substituents at position of C7.

Drug Design↗

Accurate prediction of the relative potencies of members of a series of kinase inhibitors using molecular docking and MM-GBSA scoring.

The ability of molecular docking, using the program Glide and an MM-GBSA postdocking scoring protocol, to correctly rank a number of congeneric kinase inhibitors was assessed. The approach was successful for the cases considered and suggests that this may be useful for the design of inhibitors in the lead optimization phase of drug discovery.

Aniline Compounds↗

Prediction of binding for a kind of non-peptic HCV NS3 serine protease inhibitors from plants by molecular docking and MM-PBSA method.

In the study, molecular dynamics simulations combined with MM-PBSA (Molecular Mechanics and Poisson-Boltzmann Surface Area) technique were applied to predict the binding mode of the polyphenol inhibitor in the binding pocket of the HCV NS3 serine protease for which the ligand-protein crystal structure is not available. The most favorable geometry of three candidates from molecular docking had a binding free energy about 3 and 6kcal/mol more favorable than the other two candidates, respectively, and was identified as the correct binding mode. In the mode, the correlation of the calculated and experimental binding affinities of all five polyphenol compounds is satisfactory indicated by r(2)=0.92. The most favorable binding mode suggests that two galloyl residues at 3 and 4 positions of the glucopyranose ring of the inhibitors interact with SER139, GLY137, ALA157, and ASP81 by hydrogen bond interaction and with ALA156 and HIE57 by hydrophobic interaction and are essential for the activities of the studied inhibitors.

Binding Sites↗

Molecular docking and 3D-QSAR studies on gag peptide analogue inhibitors interacting with human cyclophilin A.

The interaction of a series gag peptide analogues with human cyclophilin A (hCypA) have been studied employing molecular docking and 3D-QSAR approaches. The Lamarckian Genetic Algorithm (LGA) and divide-and-conquer methods were applied to locate the binding orientations and conformations of the inhibitors interacting with hCypA. Good correlations between the calculated interaction free energies and experimental inhibitory activities suggest that the binding conformations of these inhibitors are reasonable. A novel interaction model was identified for inhibitors 11, 15, and 17 whose N-termini were modified by addition of the deaminovaline (Dav) group and the C-termini of 15 and 17 were modified by addition of a benzyl group. Accordingly, two new binding sites (sites A and D in Figure 1) were revealed, which show a strong correlation with inhibitor potency and thus can be used as a starting point for new inhibitor design. In addition, two predictive 3D-QSAR models were obtained by CoMFA and CoMSIA analyses based on the binding conformations derived from the molecular docking calculations. The reasonable r(cross)(2) (cross-validated) values 0.738 and 0.762 were obtained for CoMFA and CoMSIA models, respectively. The predictive ability of these models was validated by four peptide analogues test set. The CoMFA and CoMSIA field distributions are in general agreement with the structural characteristics of the binding groove of hCypA. This indicates the reasonableness of the binding model of the inhibitors with hCypA. Considering all these results together with the valuable clues of binding from references published recently, reasonable pharmacophore elements have been suggested, demonstrating that the 3D-QSAR models about peptide analogue inhibitors are expected to be further employed in predicting activities of the novel compounds for inhibiting hCypA.

Binding Sites↗

Possible dynamic anchor points in a benzoxazinone derivative-human oxytocin receptor system--a molecular docking and dynamics calculation.

In this study, we performed a molecular docking and dynamics simulation for a benzoxazinone-human oxytocin receptor system to determine the possible hydrophobic and electrostatic interaction points in the dynamic complex. After the homology modeling, the ligand was docked into the putative active using AutoDock 3.05. After the application of energetic and structural filters, the complexes obtained were further refined with a simulated annealing protocol (AMBER8) to remove steric clashes. Three complexes were selected for subjection to the molecular dynamics simulation (5 ns), and the results on the occurrence of average anchor points showed a stable complex between the benzoxazinone derivative and the receptor. The complex could be used as a good starting point for further analysis with site-directed mutagenesis, or further computational research.

Animals↗

Binding investigation of human 5-lipoxygenase with its inhibitors by SPR technology correlating with molecular docking simulation.

The binding features of a series of 5-lipoxygenase (5-LOX) inhibitors (caffeic acid, NDGA, AA-861, CDC, esculetin, gossypol and phenidone) to human 5-LOX have been studied by using surface plasmon resonance biosensor (SPR) technology based Biacore 3000 and molecular docking simulation analyses. The SPR results showed that the equilibrium dissociation constant (KD) values evaluated by Biacore 3000 for the inhibitors showed a good correlation with its reported IC50, suggesting that SPR technology might be applicable as a direct assay method in screening new 5-LOX inhibitors at an early stage. In addition, the 3D structural model of 5-LOX was generated according to the crystal structure of rabbit reticulocyte 15-lipoxygenase, and the molecular docking simulation analyses revealed that the predicted binding free energies for the inhibitors correlated well with the KD values measured by SPR assay, which implies the correctness of the constructed 3D structural model of 5-LOX. This current work has potential for application in structure-based 5-LOX inhibitor discovery.

Amino Acid Sequence↗

Information decay in molecular docking screens against holo, apo, and modeled conformations of enzymes.

Molecular docking uses the three-dimensional structure of a receptor to screen a small molecule database for potential ligands. The dependence of docking screens on the conformation of the binding site remains an open question. To evaluate the information loss that occurs as the active site conformation becomes less defined, a small molecule database was docked against the holo (ligand bound), apo, and homology modeled structures of 10 different enzyme binding sites. The holo and apo representations were crystallographic structures taken from the Protein Data Bank (PDB), and the homology-modeled structures were taken from the publicly available resource ModBase. The database docked was the MDL Drug Data Report (MDDR), a functionally annotated database of 95000 small molecules that contained at least 35 ligands for each of the 10 systems. In all sites, at least 99% of the molecules in the MDDR were treated as nonbinding decoys. For each system, the holo, apo, and modeled structures were used to screen the MDDR, and the ability of each structure to enrich the known ligands for that system over random selection was evaluated. The best overall enrichment was produced by the holo structure in seven systems, the apo structure in two systems, and the modeled structure in one system. These results suggest that the performance of the docking calculation is affected by the particular representation of the receptor used in the screen, and that the holo structure is the one most likely to yield the best discrimination between known ligands and decoy molecules, but important exceptions to this rule also emerge from this study. Although each of the holo, apo, and modeled conformations led to enrichment of known ligands in all systems, the enrichment did not always rise to a level judged to be sufficient to justify the effort of a docking screen. Using a 20-fold enrichment of known ligands over random selection as a rough guideline for what might be enough to justify a docking screen, the holo conformation of the enzyme met this criterion in eight of 10 sites, whereas the apo conformation met this criterion in only two sites and the modeled conformation in three.

Animals↗

A molecular docking strategy identifies Eosin B as a non-active site inhibitor of protozoal bifunctional thymidylate synthase-dihydrofolate reductase.

Protozoal parasites are unusual in that their thymidylate synthase (TS) and dihydrofolate reductase (DHFR) enzymes exist on a single polypeptide. In an effort to probe the possibility of substrate channeling between the TS and DHFR active sites and to identify inhibitors specific for bifunctional TS-DHFR, we used molecular docking to screen for inhibitors targeting the shallow groove connecting the two active sites. Eosin B is a 100 microm non-active site inhibitor of Leishmania major TS-DHFR identified by molecular docking. Eosin B slows both the TS and DHFR reaction rates. When Arg-283, a key residue to which eosin B is predicted to bind, is mutated to glutamate, however, eosin B only minimally inhibits the TS-DHFR reaction. Additionally, eosin B was found to be a 180 microm inhibitor of Toxoplasma gondii in both biochemical and cell culture assays.

Animals↗

Molecular docking studies of a group of hydroxamate inhibitors with gelatinase-A by molecular dynamics.

We have performed docking and molecular dynamics simulations of hydroxamates complexed with human gelatinase-A (MMP-2) to gain insight into the structural and energetic preferences of these inhibitors. The study was conducted on a selected set of eleven compounds with variation in structure and activity. Molecular dynamics simulations were performed at 300 K for 100 ps with equilibration for 50 ps. The structural analyses of the trajectories indicate that the coordinate bond interactions, the hydrogen bond interactions, the van der Waals interactions as well as the hydrophobic interactions between ligand and receptor are responsible simultaneously for the preference of inhibition and potency. The ligand hydroxamate group is coordinated to the catalytic zinc ion and form stable hydrogen bonds with the carbonyl oxygen of Gly 162. The P1' group makes extensive van der Waals and hydrophobic contacts with the nonpolar side chains of several residues in the S1' subsite, including Leu 197, Val 198, Leu 218 and Tyr 223. Moreover, four to eight hydrogen bonds between hydroxamates and MMP-2 are formed to stabilize the inhibitors in the active site. Compared with the P2' and P3' groups, the P1' groups of inhibitors are oriented regularly, which is produced by the restrain of the S1' subsite. From the relationship between the length of the nonpolar P1' group and the biological activity, we confirm that MMP-2 has a pocket-like S1' subsite, not a channel-like S1' subsite proposed by Kiyama (Kiyama, R. et al., J. Med. Chem. 42 (1999), 1723). The energetic analyses show that the experimental binding free energies can be well correlated with the interactions between the inhibitors and their environments, which could be used as a simple score function to evaluate the binding affinities for other similar hydroxamates. The validity of the force field parameters and the MD simulations can be fully testified by the satisfactory agreements between the experimental structure-activity relationship and the information from the structural and energetic analyses. The information generated from the predicted complexes should be useful for further work in the area of structure-based design of new compounds.

Binding Sites↗