The SARS-CoV-2 conserved macrodomain is a mono-ADP-ribosylhydrolase.

SARS-CoV-2 has recently emerged into the human population and has led to a worldwide pandemic of COVID-19 that has caused greater than 900 thousand 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 adducts from proteins in a dynamic post-translational process increasingly recognized as an important factor that regulates viral infection. The macrodomain 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. These results are an important first step for the design and testing of potential therapies targeting this unique protein domain.