Structural insights into the substrate-binding site of main protease for the structure-based COVID-19 drug discovery.

An attractive drug target to combat COVID-19 is the main protease (Mpro ) because of its key role in the viral life cycle by processing the polyproteins translated from the viral RNA. Studying the crystal structures of the protease is important to enhance our understanding of its mechanism of action at the atomic-level resolution, and consequently may provide crucial structural insights for structure-based drug discovery. In the current study, we report a comparative structural analysis of the Mpro substrate binding site for both apo and holo forms to identify key interacting residues and conserved water molecules during the ligand-binding process. It is shown that in addition to the catalytic dyad residues (His41 and Cys145), the oxyanion hole residues (Asn142-Ser144) and residues His164-Glu166 form essential parts of the substrate-binding pocket of the protease in the binding process. Furthermore, we address the issue of the substrate-binding pocket flexibility and show that two adjacent loops in the Mpro structures (residues Thr45-Met49 and Arg188-Ala191) with high flexibility can regulate the binding cavity' accessibility for different ligand sizes. Moreover, we discuss in detail the various structural and functional roles of several important conserved and mobile water molecules within and around the binding site in the proper enzymatic function of Mpro . We also present a new docking protocol in the framework of the ensemble docking strategy. The performance of the docking protocol has been evaluated in predicting ligand binding pose and affinity ranking for two popular docking programs; AutoDock4 and AutoDock Vina. Our docking results suggest that the top-ranked poses of the most populated clusters obtained by AutoDock Vina are the most important representative docking runs that show a very good performance in estimating experimental binding poses and affinity ranking.

Binder design for targeting SARS-CoV-2 spike protein: An in silico perspective.

INTRODUCTION: The COVID-19 pandemic is now affecting all people around the world and getting worse. New antiviral medications are desperately needed other than the few approved medications that have shown no promising efficacy so far. METHODS: Here we report three blocking binders for targeting SARS-CoV-2 spike protein to block the interaction between the spike protein on the SARS-CoV-2 and the angiotensin-converting enzyme 2 (ACE2) receptors, responsible for viral homing into the alveolar epithelium type II cells (AECII). RESULTS: The design process is based on the collected natural scaffolds and using Rosetta interface for designing the binders. CONCLUSION: Based on the structural analysis, three binders were selected, and the results showed that they might be promising as new therapeutic targets for blocking COVID-19.