Moquin, S. | Search bioRxiv

bioRxiv2023

Crystal Structures of Inhibitor-Bound Main Protease from Delta- and Gamma-Coronaviruses

With the spread of SARS-CoV-2 throughout the globe to cause the COVID-19 pandemic, the threat of zoonotic transmissions of coronaviruses (CoV) has become even more evident. As human infections have been caused by alpha- and beta-CoVs, structural characterization and inhibitor design mostly focused on these two genera. However, viruses from the delta and gamma genera also infect mammals and pose potential zoonotic transmission threat. Here, we determined the inhibitor-bound crystal structures of the main protease (Mpro) from the delta-CoV porcine HKU15 and gamma-CoV SW1 from beluga whale. Comparison with the apo structure of SW1 Mpro, which we also present here, enabled identifying structural arrangements upon inhibitor binding at the active site. The binding modes and interactions of two covalent inhibitors, PF-00835231 (lufotrelvir) bound to HKU15 and GC376 bound to SW1 Mpro, reveal features that may be leveraged to target diverse coronaviruses and toward structure-based design of pan-CoV inhibitors.

biochemistry↗

bioRxiv2022

Defining the Substrate Envelope of SARS-CoV-2 Main Protease to Predict and Avoid Drug Resistance

Coronaviruses, as exemplified by SARS-CoV-2, can evolve and spread rapidly to cause severe disease morbidity and mortality. Direct acting antivirals (DAAs) are highly effective in decreasing disease burden especially when they target essential viral enzymes, such as proteases and polymerases, as demonstrated in HIV-1 and HCV and most recently SARS-CoV-2. Optimization of these DAAs through iterative structure-based drug design has been shown to be critical. Particularly, the evolutionarily conserved molecular mechanisms underlying viral replication can be leveraged to develop robust antivirals against rapidly evolving viral targets. The main protease (Mpro) of SARS-CoV-2, which is evolutionarily constrained to recognize and cleave 11 specific sites to promote viral maturation, exemplifies one such target. In this study we define the substrate envelope of Mpro by determining the molecular basis of substrate recognition, through nine high-resolution cocrystal structures of SARS-CoV-2 Mpro with the viral cleavage sites. These structures enable identification of evolutionarily vulnerable sites beyond the substrate envelope that may be susceptible to drug resistance and compromise binding of the newly developed Mpro inhibitors.

biochemistry↗