Coronavirus nucleocapsid proteins assemble constitutively in high molecular oligomers

Cong, Yingying; Kriegenburg, Franziska; de Haan, Cornelis A. M.; Reggiori, Fulvio

Previous studies have shown that the N2b/ CTD domain is required for the dimerization of N proteins of different CoVs 12, 23, 24, 27, 28 . Our consistent finding that the N protein forms oligomers suggested that there might be several domains involved in the self-interaction. We thus generated three 6xHis-tagged truncations, i.e. N1 (which contains the NTD), N2a and N2b-N3 (which contains the CTD), which collectively cover the full length of the N protein (Fig. 1a) . These constructs were expressed in E. coli and the resulting bacterial extracts were incubated with either immobilized GST or GST-N protein. Interestingly, all three analyzed N protein truncations specifically bound GST-N protein but not GST alone (Fig. 3 , top panel), further revealing that in addition to the reported N2b/CTD region, the N protein possesses binding domains for the self-interaction in the N1 and N2a parts as well.