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Transient Oligomerization of the SARS-CoV N Protein – Implication for Virus Ribonucleoprotein Packaging

2013; Public Library of Science; Volume: 8; Issue: 5 Linguagem: Inglês

10.1371/journal.pone.0065045

1932-6203

Chung‐ke Chang, Chia-Min Michael Chen, Ming-hui Chiang, Yen-lan Hsu, Tai-huang Huang,

RNA and protein synthesis mechanisms

The nucleocapsid (N) phosphoprotein of the severe acute respiratory syndrome coronavirus (SARS-CoV) packages the viral genome into a helical ribonucleocapsid and plays a fundamental role during viral self-assembly. The N protein consists of two structural domains interspersed between intrinsically disordered regions and dimerizes through the C-terminal structural domain (CTD). A key activity of the protein is the ability to oligomerize during capsid formation by utilizing the dimer as a building block, but the structural and mechanistic bases of this activity are not well understood. By disulfide trapping technique we measured the amount of transient oligomers of N protein mutants with strategically located cysteine residues and showed that CTD acts as a primary transient oligomerization domain in solution. The data is consistent with the helical oligomer packing model of N protein observed in crystal. A systematic study of the oligomerization behavior revealed that altering the intermolecular electrostatic repulsion through changes in solution salt concentration or phosphorylation-mimicking mutations affects oligomerization propensity. We propose a biophysical mechanism where electrostatic repulsion acts as a switch to regulate N protein oligomerization.