SARS-CoV-2 Nucleocapsid protein is the main structural protein of SARS-associated coronavirus (CoV) that binds the viral RNA genome. It is a recombinant protein, expressed in E.coli cells. The protein consists of 419 amino acids and an N-terminal His6-tag. The calculated molecular weight range of the His-tagged protein is 46.5 kDa.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an enveloped, positive-strand RNA virus that causes the disease COVID-19 (Coronavirus Disease-2019). The COVID-19 pandemic is a global problem among the world’s population. The diagnosis is difficult due to its unspecific symptoms. In this context, rapid and easy to implement diagnostic tools are urgently needed.
SARS-CoV-2 has four major structural proteins, including nucleocapsid (N), spike (S), membrane (M), and small envelope (E). The N protein is the only one that binds to the RNA genome and is also involved in viral assembly and budding. The SARS-CoV-2 N is a highly immunogenic multi-functional protein that can be divided into five domains: a predicted intrinsically disordered N-terminal domain (NTD), an RNA-binding domain (RBD), a predicted disordered central linker (LINK), a dimerization domain, and a predicted disordered C-terminal domain (CTD).
Detection of viral antigens can be a possible strategy to get an early diagnosis of SARS-CoV-2 infection. The nucleocapsid protein (NP) has been confirmed as the ideal target for the early detection of SARS-CoV infection, which is genetically similar to SARS-CoV-2, so that it could be detected up to 1 day before the appearance of clinical symptoms.