Fig. 2.

The mechanism of replication of newly emerged SARS-CoV-2. The spike protein (S) of COVID-19 binds to the ACE-2 membrane receptor, which is facilitated by the protease, named TMPRSS2, and enters the cell. After the entry of viral RNA into the cell, the translocation of open reading frame-1a and 2b (ORF-1a and ORF-2b) produced two major types of polyproteins, namely pp1a and pp1ab (yellow box) to yield 16 different types of nonstructural proteins (nsps) and help in proteolysis (skybox) and form the replicating-transcriptional complex (RTC; red), which yield in a negative-sense RNAs (-RNA) (blue line). These newly formed (−) RNAs act as template strands for the formation of positive-sense RNA of the viral genome (green lines). The transcription in (−) RNAs further leads to the synthesis of accessory and structural proteins (green lines). Finally, the genomic RNA and structural proteins are assembled into a viral nucleocapsid by ER (blue) and move to Golgi intermediate compartment (brown) for envelope formation and released outside the cell by exocytosis [41,112,113]. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)