Table 2.

Comparison of protein composition, functional receptor and infected mammalian cells of SARS-CoV, MERS-CoV and SARS-CoV-2 [1,[15], [16], [17], [18], [19], [20], [21], [22]].

	Protein content	Functional receptor	Infected mammalian cells
SARS-CoV	Replicase polyproteins: pp1a, pp1ab Structural proteins: spike (S) glycoprotein, membrane (M), envelope (E), nucleocapsid (N) 8 putative proteins	ACE2	airway epithelium, type I and type II pneumocytes, alveolar macrophages
MERS-CoV	Structural proteins: spike (S) glycoprotein, membrane (M), envelope (E), nucleocapsid (N)	hDPP4	airway epithelium, type I and type II pneumocytes
SARS-CoV-2	Non-structural proteins forming replicase-transcriptase complex: Nsp1-Nsp16 Structural proteins: spike (S) glycoprotein, membrane (M), envelope (E), nucleocapsid (N) 9 accessory factors	ACE2	types I and II pneumocytes, alveolar macrophages

SARS-CoV, Severe Acute Respiratory Syndrome Coronavirus; MERS-CoV, Middle East Respiratory Syndrome Coronavirus; SARS-CoV-2, Severe Acute Respiratory Syndrome Coronavirus 2; ACE2, Angiotensin-Converting Enzyme 2; hDPP4, human dipeptidyl peptidase 4.