Elucidation of the stability and functional regions of the human coronavirus OC43 nucleocapsid protein
Chun‐Yu Huang, Yen‐Lan Hsu, Wan‐Ling Chiang, Ming‐Hon Hou
Human coronavirus OC43 (HCoV‐OC43) is one of the causes of the “common cold” in human during seasons of cold weather. The primary function of the HCoV‐OC43 nucleocapsid protein (N protein) is to recognize viral genomic RNA, which leads to ribonucleocapsid formation. Here, we characterized the stability and identified the functional regions of the recombinant HCoV‐OC43 N protein. Circular dichroism and fluorescence measurements revealed that the HCoV‐OC43 N protein is more highly ordered and stabler than the SARS‐CoV N protein previously studied. Surface plasmon resonance (SPR) experiments showed that the affinity of HCoV‐OC43 N protein for RNA was approximately fivefold higher than that of N protein for DNA. Moreover, we found that the HCoV‐OC43 N protein contains three RNA‐binding regions in its N‐terminal region (residues 1–173) and central‐linker region (residues 174–232 and 233–300). The binding affinities of the truncated N proteins and RNA follow the order: residues 1–173–residues 233–300 > residues 174–232. SPR experiments demonstrated that the C‐terminal region (residues 301–448) of HCoV‐OC43 N protein lacks RNA‐binding activity, while crosslinking and gel filtration analyses revealed that the C‐terminal region is mainly involved in the oligomerization of the HCoV‐OC43 N protein. This study may benefit the understanding of the mechanism of HCoV‐OC43 nucleocapsid formation.
Circular dichroism, Secondary structure, Thermal stability, Biochemistry