The Nsp3c protein consists of multiple domains and is likely involved in RNA replication and processing. It is sequential to the macro or “X” domain (Nsp3b), a conserved domain in many virus polypeptides with a three layer α/β/α sandwich fold, which exhibits ADP-ribose binding properties and ADP-r hydrolase activity. Two Nsp3c domains exhibit significant structural similarities and were initially found in SARS-CoV; namely SARS Unique Domains (SUDs). A third domain following the two domains, exhibiting a macro-like fold, is the last part of the Nsp3c fragment. The three domains are referred as SUD N, SUD M for middle domain and SUD C.
1H, 15N HSQC spectra of single SUDs of Nsp3c from SARS-Cov-2 as well as double domain constructs were recorded by the group of Prof. Dr. Georgios A. Spyroulias from the University of Patras, Greece.