Fig. 2.

Schematic of the gene organization on the FCoV genome. A cap structure at the 5′ end and the 3′ end poly-adenylated tail are typical structures on an RNA used as message for generating protein within a cell. The entire genome is approximately 29,000 nucleotide bases in length. The overlapping ORFs 1a and 1b encode proteins involved in RNA synthesis required for generating mRNA, the genome, and their negative sense templates. The spike refers to the gene encoding the highly glycosylated spike protein (S), Mem refers to the gene encoding the membrane protein (M), env refers to the gene encoding the envelope protein (E), and nucleocapsid refers to the gene encoding the nucleocapsid protein (N).