Open Access

F. Cantini, L. Banci, Nadide Altincekic, Jasleen Kaur Bains, Karthikeyan Dhamotharan, Christin Fuks, Boris Fürtig, S. L. Gande, Bruno Hargittay, Martin Hengesbach, Marie Hutchison, Sophie M. Korn, Nina Kubatova, Felicitas Kutz, Verena Linhard, Frank Löhr, Nathalie Meiser, Dennis Joshua Pyper, Nusrat Qureshi, Christian Richter, Krishna Saxena, Andreas Schlundt, Harald Schwalbe, Sridhar Sreeramulu, Jan-Niklas Tants, Anna Wacker, Julia E. Weigand, Jens Wöhnert, A. C. Tsika, N. K. Fourkiotis, G. A. Spyroulias

• The SARS-CoV-2 genome encodes for approximately 30 proteins. Within the international project COVID19-NMR, we distribute the spectroscopic analysis of the viral proteins and RNA. Here, we report NMR chemical shift assignments for the protein Nsp3b, a domain of Nsp3. The 217-kDa large Nsp3 protein contains multiple structurally independent, yet functionally related domains including the viral papain-like protease and Nsp3b, a macrodomain (MD). In general, the MDs of SARS-CoV and MERS-CoV were suggested to play a key role in viral replication by modulating the immune response of the host. The MDs are structurally conserved. They most likely remove ADP-ribose, a common posttranslational modification, from protein side chains. This de-ADP ribosylating function has potentially evolved to protect the virus from the anti-viral ADP-ribosylation catalyzed by poly-ADP-ribose polymerases (PARPs), which in turn are triggered by pathogen-associated sensing of the host immune system. This renders the SARS-CoV-2 Nsp3b a highly relevant drug target in the viral replication process. We here report the near-complete NMR backbone resonance assignment (1H, 13C, 15N) of the putative Nsp3b MD in its apo form and in complex with ADP-ribose. Furthermore, we derive the secondary structure of Nsp3b in solution. In addition, 15N-relaxation data suggest an ordered, rigid core of the MD structure. These data will provide a basis for NMR investigations targeted at obtaining small-molecule inhibitors interfering with the catalytic activity of Nsp3b.