Fig. 1.

A Schematic structure of coronaviruses [127]. B Schematic representation of the genome organization and functional domains of S protein for SARS-CoV, MERS-CoV and SARS-CoV-2. Reproduced with permission from [127, 128]. The genomes of CoVs consist of 2 partially overlapping replicase open reading frames (OFR1a and 1b) and several downstream ORFs that encode viral functional structural proteins and other proteins with unknown function. 50-UTR and 30-UTR, untranslated regions at the N and C-terminal regions, respectively. Kb, kilobase; pair SP, signal peptide; NTD, the N-terminal domain; RBD, receptor-binding domain; RBM, receptor-binding motif; FP, fusion peptide; HR1 and HR2, heptad repeat 1 and 2; TM, transmembrane domain; CP, cytoplasmic domain