Beneath its envelope membrane, the new coronavirus SARS-CoV-2 consists of a icosaedric nucleocapsid that contains its genectic information in form of positive sensed single-stranded RNA. The RNA is contained in a nucleoprotein complex, consisting of the SARS-CoV-2 (COVID-19) Nucleocapsid protein. This phosphoprotein is necessary to keep the capsid in its helical symmetry and aids with packaging into the viral capsid by acting as a molecular RNA chaperone. Together with the matrix (M) protein, the N-protein is one of the most abundant proteins in the viral particle, it is important for viral replication and is also known for modulating cellular signalling. It is highly immunogenic and its sequence is very conserved, mainly in the N-termnal domain. Therefore, the N-terminal truncated variant is often preferred for diagnostic purposes to minimize false positive results.
