Abstract: Objective To explore the conditions of the expression and purification of nucleocapsid proteins of human coronaviruses SARS-CoV, HCoV-229E, HCoV-OC43, HCoV-NL63 and HCoV-HKU1, animal coronaviruses bovine coronavirus, murine hepatitis virus, feline infectious peritonitis virus, and infectious bronchitis virus. Methods The pET-30a-based recombinant plasmids containing full length nucleocapsid(N) protein of coronaviruses were transformed into E.coil BL21(DE3) competent cells and were induced to express N proteins by IPTG. The expression products were purified by ion exchange chromatography and Ni 2+ affinity chromatography, and were verified by SDS-PAGE and Western blot. Results Nine coronavirus nucleocapsid proteins with correct Mr were solubly expressed and highly purified with purity >90%. Conclusion Successfully expressed nine recombinant nucleocapsid proteins with high purity in E. Coli，which provides materials to study the function of these coronavirus N proteins.

Key words: SARS-CoV, Nucleocapsid protein, Purification