Repurposing of antiparasitic drugs against the NS2B-NS3 protease of the Zika virus

To date, no approved drugs are available to treat the Zika virus (ZIKV) infection. Therefore, it is necessary to urgently identify potential drugs against the ZIKV infection. Here, the repurposing of 30 antiparasitic drugs against the NS2B-NS3 protease of the ZIKV has been carried out by using combined docking and molecular dynamics- (MD) simulations. Based on the docking results, 5 drugs, such as Amodiaquine, Primaquine, Paromomycin, Dichlorophene, and Ivermectin were screened for further analysis by MD simulations and free energy calculations. Among these drugs, Amodiaquine and Dichlorophen are found to produce the most stable complexes and possess relative binding free energies of about -44.3 ± 3.7 kcal/mol and -41.1 ± 5.3 kcal/mol respectively. Therefore, they would act as potent small-molecule inhibitors of the ZIKV protease.However, evaluations of biological and safety activities of these drugs against the ZIKV protease are required before their clinical use.Communicated by Ramaswamy H. Sarma.

Peptide inhibitors derived from the nsp7 and nsp8 cofactors of nsp12 targeting different substrate binding sites of nsp12 of the SARS-CoV-2

SARS-COV-2 is responsible for the COVID-19 pandemic, which has infected more than 767 million people worldwide including about 7 million deaths till 5 June 2023. Despite the emergency use of certain vaccines, deaths due to COVID-19 have not yet stopped completed. Therefore, it is imperative to design and develop drugs that can be used to treat patients suffering from COVID-19. Here, two peptide inhibitors derived from nsp7 and nsp8 cofactors of nsp12 have been shown to block different substrate binding sites of nsp12 that are mainly responsible for the replication of the viral genome of SARS-CoV-2. By using the docking, molecular dynamics (MD), and MM/GBSA techniques, it is shown that these inhibitors can bind to multiple binding sites of nsp12, such as the interface of nsp7 and nsp12, interface of nsp8 and nsp12, RNA primer entry site, and nucleoside triphosphate (NTP) entry site. The relative binding free energies of the most stable protein-peptide complexes are found to lie between ∼-34.20 ± 10.07 to -59.54 ± 9.96 kcal/mol. Hence, it is likely that these inhibitors may bind to different sites of nsp12 to block the access of its cofactors and the viral genome, thereby affecting the replication. It is thus proposed that these peptide inhibitors may be further developed as potential drug candidates to suppress the viral loads in COVID-19 patients.Communicated by Ramaswamy H. Sarma.

Computational analysis of protein-ligand interaction by targeting a cell cycle restrainer

BACKGROUND AND OBJECTIVE

The cyclin-dependent kinases 4/6 (CDK4/6) are among the most crucial controllers of the cell cycle, and their abnormal activity may induce uncontrolled cell multiplication, leading to cancers. The FDA currently approved three CDK4/6 inhibitors, however, they are associated with a variety of side effects. Thus it is required to design/develop novel potent and safe CDK4/6 inhibitors.

METHODS

In the present work, we furnished an integrated in-silico approach followed by steered molecular dynamics (SMD) simulations to identify molecules that can be developed into novel CDK4/6 inhibitors.

RESULTS

Out of thirty-two 3-methyleneisoindolin-1-one molecules we selected top three M18, M24, and M32 molecules as potential drug candidates based on their respective interaction energies. According to the robust 250 ns MD simulations and thermodynamic free energy, M24 was the best molecule in comparison to palbociclib. In SMD, M24 required ∼205.587 kJ/mol/nm external pulling force, while palbociclib needed ∼160.97 kJ/mol/nm to dissociate from the binding pocket of the CDK4.

CONCLUSIONS

The high pulling force required for M24 dissociation from the binding site denotes stronger binding with CDK4. Therefore, M24 offers the possibility of a critical starting structure in developing effective CDK4 inhibitors.

Structures and dynamics of peptide and peptidomimetic inhibitors bound to the NS2B-NS3 protease of the ZIKA virus

Infections caused by the Zika virus (ZIKV) have detrimental effects on human health, in particular on infants. As no potent drug or vaccine is available to date to contain this viral disease, it is necessary to design inhibitors that can target the NS2B-NS3 protease of the ZIKV, which is mainly responsible for the proliferation of the virus inside the host cells . Here, molecular dynamics (MD) simulation and molecular mechanics energies combined with the generalized Born and surface area continuum solvation model (MM/GBSA) are used to understand the binding modes and stabilities of R, KR, KKR, WKR, WKKR, YKKR, and FKKR peptide inhibitors bound to the NS3-NS2B protease. The results are compared with the corresponding results obtained for covalent (compound 1) and non-covalent (compound 4*) peptidomimetic inhibitors . It is revealed that peptide inhibitors can bind strongly with the ZIKV protease with the ΔG_bind ranging from -12 kcal/mol to -73 kcal/mol. Among these peptides, YKKR is found to make the most stable complex with the protease and fully occupy the electrostatically active substrate binding site. Hence, it would inhibit the protease activities of ZIKV strongly. The residue-wise decomposition of ΔG_bind indicates that Asp75, Asp129, Tyr130, Ser135, Gly151, Asn152, Glys153, and Tyr161 of NS3 and Ser81, Asp83, and Phe84 of NS2B play a prominent role in the inhibitor binding. Therefore, any future design of inhibitors should be aimed to target these residues.

Room-Temperature Plasticity of a Nanosized GaN Crystal

GaN wurtzite crystal is commonly regarded as eminently brittle. However, our research demonstrates that nanodeconfined GaN compressed along the M direction begins to exhibit room-temperature plasticity, yielding a dislocation-free structure despite the occurrence of considerable, irreversible deformation. Our interest in M-oriented, strained GaN nanoobjects was sparked by the results of first-principles bandgap calculations, whereas subsequent nanomechanical tests and ultrahigh-voltage (1250 kV) transmission electron microscopy observations confirmed the authenticity of the phenomenon. Moreover, identical experiments along the C direction produced only a quasi-brittle response. Precisely how this happens is demonstrated by molecular dynamics simulations of the deformation of the C- and M-oriented GaN frustum, which mirror our nanopillar crystals.

Structural based study to identify new potential inhibitors for dual specificity tyrosine-phosphorylation- regulated kinase

Background and Objectives The Dual-specificity tyrosine-phosphorylation regulated kinase-1A (DYRK1A) a serine/threonine kinase that has freshly gained recognition as an essential drug target due to the discovery of its involvement in pathological diseases. The development of new potent inhibitors of DYRK1A would contribute to clarify the molecular mechanisms of associated diseases. It would administer a new lead compound for molecular-targeted protein, which was the primary focus of our study. Methods The library of in-house synthesized pyrrolone-fused benzosuberene (PBS) compounds was docked with DYRK1A receptor. Further, molecular mechanics-Poisson Boltzmann surface area (MM-PBSA) estimations were conducted to confirm our docking outcomes and compared the stability of chosen complexes with the 2C3 (standard molecule) complex. Results This study reports Ligand15, Ligand14, and Ligand11 as potent inhibitors which showed higher ligand efficiency, binding affinity, lipophilic ligand efficiency, and favorable torsion values as compared to 2C3. Conclusion The stated methodologies revealed a unique mechanism of active site binding. The binding interactions within the active site showed that the chosen molecules had notable interactions than the standard molecule, which led to the generation of potential compounds to inhibit DYRK1A.

Mechanistic insights into the Orai channel by molecular dynamics simulations

Highly Ca²⁺ selective channels trigger a large variety of cellular signaling processes in both excitable and non-excitable cells. Among these channels, the Orai channel is unique in its activation mechanism and its structure. It mediates Ca²⁺ influx into the cytosol with an extremely small unitary conductance over longer time-scales, ranging from minutes up to several hours. Its activation is regulated by the Ca²⁺ content of the endoplasmic reticulum (ER). Depletion of luminal [Ca²⁺]_ER is sensed by the STIM1 single transmembrane protein that directly binds and gates the Orai1 channel. Orai mediated Ca²⁺ influx increases cytosolic Ca²⁺ from 100 nM up to low micromolar range close to the pore and thereby forms Ca²⁺ microdomains. Hence, these features of the Orai channel can trigger long-term signaling processes without affecting the overall Ca²⁺ content of a single living cell. Here we focus on the architecture and dynamic conformational changes within the Orai channel. This review summarizes current achievements of molecular dynamics simulations in combination with live cell recordings to address gating and permeation of the Orai channel with molecular precision.