Modular organization of SARS coronavirus nucleocapsid protein

Chang, Chung-ke; Sue, Shih-Che; Yu, Tsan-hung; Hsieh, Chiu-Min; Tsai, Cheng-Kun; Chiang, Yen-Chieh; Lee, Shin-jye; Hsiao, Hsin-hao; Wu, Wen-Jin; Chang, Wei-Lun; Lin, Chun-Hung; Huang, Tai-huang

The SARS-CoV nucleocapsid (N) protein is a major antigen in severe acute respiratory syndrome. It binds to the viral RNA genome and forms the ribonucleoprotein core. The SARS-CoV N protein has also been suggested to be involved in other important functions in the viral life cycle. Here we show that the N protein consists of two non-interacting structural domains, the N-terminal RNA-binding domain (RBD) (residues 45–181) and the C-terminal dimerization domain (residues 248–365) (DD), surrounded by flexible linkers. The C-terminal domain exists exclusively as a dimer in solution. The flexible linkers are intrinsically disordered and represent potential interaction sites with other protein and protein-RNA partners. Bioinformatics reveal that other coronavirus N proteins could share the same modular organization. This study provides information on the domain structure partition of SARS-CoV N protein and insights into the differing roles of structured and disordered regions in coronavirus nucleocapsid proteins.