Functions of NSPs encoded by ORF1a and 1b of SARS-CoV-2

NSP proteinsPossible biological functionsReferences
Nsp1Inhibit translation of host proteins through r-mRNA binding[58]
Nsp2Disruption of host cell environment by binding with prohibitin-1 and 2[68]
Nsp3 (a PLpro), largest nsp with 1,299 aa)Viral polyprotein processing[68]
Nsp4Viral replication and formation of transcription complexes[68]
Nsp5Viral polyprotein processing[68]
Nsp6 (a 3C-like protease)Viral replication and formation of transcription complexes, biogenesis of replication organelle[6, 7, 9]
Nsp7Accessory factors of RdRP, stabilization of the replication/transcription complex, SARS-CoV nsp7 enhances RNA binding by nsp8[68]
Nsp8Accessory factors of RdRP, stabilization of the replication/transcription complex[68]
Complex formed between Nsp7+8 nsp(7+8)It is a unique multimeric RNA polymerase capable of both de novo initiation and primer extension activity, and is an accessory factor for RdRP[68]
Nsp9RNA-binding protein[68, 10, 11]
Nsp10Cofactor of nsp14 and nsp16, Nsp14−Nsp10 complex enhances translation inhibition, which is executed by NSP14 consequently abolishing the IFN-I-dependent induction of ISGs[68, 12]
Nsp11 (smallest nsp with 13 aa)Intrinsically disordered protein with unknown function[69, 12, 13]
Nsp12It is an RdRP in addition to being a nucleotidyl-transferase[6, 7, 13]
Nsp13It is a helicase with a possible function in nucleic acid metabolism including DNA replication, recombination, transcription, repair, ribosome biogenesis, RNA processing, translation, and decay[68, 13]
Nsp14It is a proofreading 3’–5’ exoribonuclease and a guanosine-N7 methyltransferase (N7-MTase) for the RNA cap formation, effects of viral infection on the host cell transcriptome, Nsp14−Nsp10 complex enhances translation inhibition, which is executed by NSP14 consequently abolishing the IFN-I-dependent induction of ISGs[68, 12, 13]
Nsp15 and 16Nsp15 is a uridine-specific endoribonuclease and IFN antagonist, whereas the Nsp16 is ribose 2′-O-methyltransferase for gRNA cap formation[68, 12, 13]

aa: amino acids; RdRP: RNA-dependent RNA polymerase; ISGs: IFN stimulated genes; gRNA: genomic RNA; mRNA: messenger RNA; r-mRNA: ribosomal-mRNA