Table 2.

Accessory proteins of SARS CoV-2 and their function.

Accessory proteins	Amino acid (aa)	Functiona	Reference
ORF3a	275 aa	Involved in formation of ion channels, virulence, infectivity and virus release	[52,20]
ORF3b	22 aa	Strong INF-1 antagonist.	[53]
ORF6	61 aa	Interacts with viral NSP8 (enhancing RNA polymerase activity) and involved in viral pathogenesis	[20]
ORF7a	121 aa	Inhibits activity of bone marrow stromal antigen 2 (BST-2) by blocking its glycosylation.	[54]
ORF7b	43 aa	Both accessory protein and structural component of the SARS virion.	[55]
ORF8	121 aa	Important for adaptation in human host following interspecies transmission and virus replicative efficiency.	[[56], [57], [58]]
ORF9b	97 aa	Interacts with a mitochondrial import receptor, Tom70, which acts as an essential adaptor linking MAVS to TBK1/IRF3; resulting in the activation of IRF-3	[59,60]
ORF9c	XX aa	Interacts with multiple proteins that modify IkB kinase and NF-kB signalling pathway, including NLRX1, F2RL1 and NDFIP2.	[60]
ORF10	38 aa	Function is undefined	[20]

^aNote: The functions of accessory proteins are reported for SARS-CoV and are considered to be similar in SARS-CoV-2.