The SARS-CoV-2 conserved macrodomain is a highly efficient ADP-ribosylhydrolase enzyme.bioRxiv. 2020 May 12B
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other SARS-like-CoVs encode 3 tandem macrodomains within non-structural protein 3 (nsp3). The first of these macrodomains, termed Mac1, is conserved throughout CoVs, binds to mono- and poly-ADP-ribose, and hydrolyzes mono-ADP-ribose (MAR) from target proteins. Mac1 is essential for pathogenesis in multiple animal models of CoV infection, implicating this domain as a prominent virulence factor and potential therapeutic target. Mac1 likely counters host-mediated antiviral ADP-ribosylation, a posttranslational modification that is part of the host response to viral infections. Here we report the crystal structure of SARS-CoV-2 Mac1 in complex with ADP-ribose refined at 2.2 Å resolution. SARS-CoV-2, SARS-CoV and MERS-CoV Mac1 exhibit similar structural folds and ADP-ribose binding modes as shown by structural comparison. All three CoV Mac1 proteins bound to ADP-ribose with low μM affinities. They also demonstrated highly efficient de-MARylating activity, which was greater than that of the human Mdo2 macrodomain. We conclude that the SARS-CoV-2 and other CoV Mac1 proteins are highly efficient ADP-ribosylhydrolases with strikingly similar activity, indicating that compounds targeting CoV Mac1 proteins may have broad antiviral activity against CoVs.
SARS-CoV-2 has recently emerged into the human population and has led to a worldwide pandemic of COVID-19 that has caused nearly 300K deaths worldwide. With, no currently approved treatments, novel therapeutic strategies are desperately needed. All coronaviruses encode for a highly conserved macrodomain (Mac1) that binds to and removes ADP-ribose, a post-translation modification, from proteins. This protein domain is essential for CoV pathogenesis and may be a novel therapeutic target. Thus, understanding its biochemistry and enzyme activity are critical first steps for these efforts. Here we report the crystal structure of SARS-CoV-2 Mac1 in complex with ADP-ribose, and describe its ADP-ribose binding and hydrolysis activities in direct comparison to SARS-CoV and MERS-CoV Mac1 proteins, and a human macrodomain. These results are an important first step for the design and testing of potential therapies targeting this unique protein domain.