3.10. Nucleocapsid protein (N protein)
The N proteins of the SARS-CoV-2 and the BatCoV RatG13 contain 419 amino acids each while that of SARS-CoV contains 422 amino acids (Table.1). N proteins of the SARS-CoV-2 and the SARS-CoV are 90.5% identical and 94.3% similar while those of the SARS-CoV-2 and the BatCoV RaTG13 are 99% identical and similar (Table.2). The N- protein is an RNA binding protein with three domains: N- terminal domain that binds the RNA, C- terminal domain responsible for dimerization, and a disordered central region rich in serine and arginine (SR) [49].
The N protein is essential for the formation of the helical viral RNA, induction of the replication and transcription of the virus, and control of the host cells metabolism so as to ensure the viral replication process and to regulate the host cell apoptosis and cell cycle [49-51]. Moreover, the N protein is very immunogenic and it induces the host immune system to respond against the SARS-CoV [52].