SARS-CoV-2 non-structural protein 12 Nidovirus RNA-dependent RNA polymerase-associated nucleotidyltransferase domain (nsp12 NiRAN) (nsp12 NiRAN)

The SARS-CoV-2 nsp12 NiRAN domain is a specialized N-terminal region of the non-structural protein 12, which functions as the core RNA-dependent RNA polymerase (RdRp) of the virus (UniProtKB - P0DTD1) [4]. While the RdRp domain is responsible for RNA synthesis, the NiRAN (Nidovirus-specific RdRp-associated nucleotidyltransferase) domain exhibits essential nucleotidyltransferase activity required for viral replication and mRNA capping (Lehmann et al., 2021) [1]. It catalyzes the transfer of a nucleoside monophosphate (NMP) to the N-terminus of the viral protein nsp9, a step that is vital for the assembly of the replication-transcription complex (Yin et al., 2021) [2]. Because this domain is unique to the Nidovirales order and lacks a direct human homolog, it represents a highly specific therapeutic target for antiviral development. Compounds such as suramin and the active metabolite of bemnifosbuvir (AT-527) have been identified as potent inhibitors of the NiRAN domain, effectively blocking the viral life cycle (Good et al., 2021) [3]. Targeting this site offers a strategic advantage in overcoming resistance to traditional RdRp inhibitors like remdesivir.

Other names

NiRAN domainnsp12 N-terminal domainNidovirus-specific RdRp-associated nucleotidyltransferaseSARS-CoV-2 nsp12 NiRAN

Inhibition of the nucleotidyltransferase activity of the NiRAN domain, which prevents the UMPylation/GMPylation of nsp9 and subsequent viral RNA capping and replication initiation (Lehmann et al., 2021; Yin et al., 2021).