Structure, interface stability and hot-spots identification for RBD(SARS-CoV-2):hACE2 complex formation

Inhibition of SARS-CoV-2 pathogenesis by potent peptides designed by the mutation of ACE2 binding region

The outbreak of COVID-19 has resulted in millions of deaths. Despite all attempts that have been made to combat the pandemic, the re-emergence of new variants complicated SARS-CoV-2 eradication. The ongoing global spread of COVID-19 demands the incessant development of novel agents in vaccination, diagnosis, and therapeutics. Targeting receptor-binding domain (RBD) of spike protein by which the virus identifies host receptor, angiotensin-converting enzyme (ACE2), is a promising strategy for curbing viral infection. This study aims to discover novel peptide inhibitors against SARS-CoV-2 entry using computational approaches. The RBD binding domain of ACE2 was extracted and docked against the RBD. MMPBSA calculations revealed the binding energies of each residue in the template. The residues with unfavorable binding energies were considered as mutation spots by OSPREY. Binding energies of the residues in RBD-ACE2 interface was determined by molecular docking. Peptide inhibitors were designed by the mutation of RBD residues in the virus-receptors complex which had unfavorable energies. Peptide tendency for RBD binding, safety, and allergenicity were the criteria based on which the final hits were screened among the initial library. Molecular dynamics simulations also provided information on the mechanisms of inhibitory action in peptides. The results were finally validated by molecular docking simulations to make sure the peptides are capable of hindering virus-host interaction. Our results introduce three peptides P7 (RAWTFLDKFNHEAEDLRYQSSLASWN), P13 (RASTFLDKFNHEAEDLRYQSSLASWN), and P19 (RADTFLDKFNHEAEDLRYQSSLASWN) as potential effective inhibitors of SARS-CoV-2 entry which could be considered in drug development for COVID-19 treatment.

Evaluating the conformational space of the active site of D2 dopamine receptor. Scope and limitations of the standard docking methods

We report here for the first time the potential energy surfaces (PES) of phenyletilamine (PEA) and meta-tyramine (m-OH-PEA) at the D₂ dopamine receptor (D2DR) binding site. PESs not only allow us to observe all the critical points of the surface (minimums, maximums, and transition states), but also to note the ease or difficulty that each local minima have for their conformational inter-conversions and therefore know the conformational flexibility that these ligands have in their active sites. Taking advantage of possessing this valuable information, we analyze how accurate a standard docking study is in these cases. Our results indicate that although we have to be careful in how to carry out this type of study and to consider performing some extra-simulations, docking calculations can be satisfactory. In order to analyze in detail the different molecular interactions that are stabilizing the different ligand-receptor (L-R) complexes, we carried out quantum theory of atoms in molecules (QTAIM) computations and NMR shielding calculations. Although some of these techniques are a bit tedious and require more computational time, our results demonstrate the importance of performing computational simulations using different types of combined techniques (docking/MD/hybrid QM-MM/QTAIM and NMR shielding calculations) in order to obtain more accurate results. Our results allow us to understand in details the molecular interactions stabilizing and destabilizing the different L-R complexes reported here. Thus, the different activities observed for dopamine (DA), m-OH-PEA, and PEA can be clearly explained at molecular level.