Table 17.1.

Coronavirus nsps That form the Replicase/Transcriptase Complex*

Nonstructural protein	Function
nsp1	Interferon antagonist (not present in all coronaviruses)
nsp2	Not known
nsp3	Papain-like protease domains and several other protein interaction domains. May tether the RNA genome to the replicase/transcriptase complex.
nsp4	Transmembrane scaffold. Involved in membrane remodeling.
nsp5	Main protease (Mpro) (also called 3C-like protease)
nsp6	Transmembrane scaffold. Involved in membrane remodeling.
nsp7	Forms a large complex with nsp8.
nsp8	Forms a large complex with nsp7. The complex may function as a processivity clamp for the RdRp.
nsp9	Single-stranded RNA-binding protein
nsp10	Zinc-binding cofactor for 2′-O-methyltransferase (nsp16)
nsp12	RdRp
nsp13	RNA 5′ triphosphatase (cap synthesis), RNA helicase
nsp14	N7-methyltransferase, Exo N 3′–5′ exonuclease (provides a proofreading function for the coronavirus RdRp)
nsp15	Nendo U endonuclease (cleaves single- and double-stranded RNA downstream of uridylate residues, producing 2–3 cyclic phosphates).
nsp16	2′-O-methyltransferase (cap synthesis)

*Products of polyproteins 1a and 1b.