Fig. 1

The genome and virion structure of coronaviruses (CoVs). a The genome structure of SARS-CoV, MERS-CoV, and SARS-CoV-2 [12,13,14]. The 5′-terminus of the CoV genome contains two overlapping open reading frames (ORFs): ORF 1a and ORF 1b, spanning two-thirds of the genome length. ORF 1a and ORF 1ab can be translated into two polyproteins (pp), pp1a and pp1ab, which are further cleaved into 16 non-structural proteins (Nsps). The 3′-terminus of the CoV genome encodes four major structural proteins in the order of spike (S), envelope (E), membrane (M), and nucleocapsid (N) proteins. Genus-specific accessory proteins are also encoded at the 3′-terminus of the CoV genome. b The virion structure of SARS-CoV-2 [16]. The spike (S), envelope (E), membrane (M) proteins form the envelope of the CoV, and the nucleocapsid (N) proteins form the capsid to pack the genomic RNA. The spike protein binds to angiotensin converting enzyme 2 (ACE2) on the cell membrane, which allows the virus to enter the cell. (Created with BioRender.com.)