Expression, purification and sublocalization of SARS-CoV nucleocapsid protein in insect cells

The causative agent of severe acute respiratory syndrome (SARS) is a previously unidentified coronavirus, SARS-CoV. The nucleocapsid (N) protein of SARS-CoV is a major viral protein recognized by acute and early convalescent sera from SARS patients. To facilitate the studies on the function and structure of the N protein, this report describe the expression and purification of recombinant SARS-CoV N protein using the baculovirus expression system. Recombinant hexa-histidine-tagged N protein with a molecular mass of 47 kD was produced in insect cells. Recombinant N protein was purified to near homogeneity by Ni2+-NTA affinity chromatography. In addition, we examined the subcellular localization of the N protein by confocal microscopy in Trichoplusia ni BT1 Tn 5B1-4 cells infected with recombinant baculovirus. The N protein was found localized in the cytoplasm as well as in the nucleolus. The purified recombinant N protein can be used in further functional study of SARS-CoV.