Table 1.

Summary of SARS-CoV-2 and the two FCoV serotypes. The spike glycoprotein of coronaviruses, mediated by proteolytic cleavage, is the main driver of cellular receptor binding and membrane fusion. The taxonomic classification, host receptor, and S1/S2 and S2′ proteolytic cleavage site amino acid sequences are summarized below.

Virus	Group	Receptor	Consensus S1/S2 Sequence in Circulating Viruses	Consensus S2′ Sequence in Circulating Viruses
SARS-CoV-2	Betacoronavirus	ACE2	SPRRAR|S (*SHRRAR|S and SRRRAR|S)	SKPSKR|S
FCoV-1	Alphacoronavirus (“clade A”)	unknown	SRRSRR|S (in FECV; mutated in FIPV)	KR|S
FCoV-2	Alphacoronavirus (“clade B”)	APN	not present	YRKR|S

*, Replaced in Common Variants.