The N protein of PEDV
The N protein of PEDV, consisting of 441 amino acids, is the only phosphorylated nucleocapsid protein among the known structural proteins of coronaviruses. Previous investigation on the cellular distribution of the N protein indicated that it is mainly located in the cytoplasm, with some N proteins in the nucleus of PEDV infected Vero cells (Shi D et al., 2014). The multifunctional property of the N protein manifests in several aspects: 1) it is bound by viral RNA to provide a structural basis for the helix nucleocapsid, while the resultant product is recognized by M protein through the interaction between the N protein and C-terminal domain of the M protein (aa237-252), and then packaged into virus particles to form the core of coronavirus (Shi D et al., 2017); 2) as an alkaline phosphoprotein, the N protein is also associated with virus replication and transcription (YW, S, H, J, & DX, 2006); 3) its participation in the biological processes related to PEDV survival has been affirmed (Shi D et al., 2017; K. N et al., 2019); 4) its localization in the nucleus may be associated with the regulation of host cell cycle and the promotion of PEDV replication process (X et al., 2013). For instance, the interaction of it with Nucleophosmin 1 (NPM1) protects NPM1 from proteolysis, thereby improving cell survival rate and affecting the replication process of PEDV (Shi D et al., 2017).