Coronavirus replication-transcription complex: Vital and selective NMPylation of a conserved site in nsp9 by the NiRAN-RdRp subunit

The Nidovirales is an order that includes Coronaviridae, Arteriviridae and 12 other families, whose RNA-dependent RNA polymerase (RdRp) is linked to an amino-terminal domain called NiRAN. The NiRAN-RdRp has a divalent cation-dependent NMPylation activity that catalyzes the transfer of a single nucleoside monophosphate to nonstructural protein 9 (nsp9) of SARS-CoV-2. Nsp9 is an RNA-binding protein that modulates viral replication, whose function requires the NMPylation in the N-terminus.