Elsevier

Antiviral Research

Volume 103, March 2014, Pages 39-50
Antiviral Research

Review
The SARS coronavirus nucleocapsid protein – Forms and functions

https://doi.org/10.1016/j.antiviral.2013.12.009 Get rights and content

Highlights

  • Coronavirus N proteins share the same modular organization.

  • Structures of SARS-CoV N protein provide insight into nucleocapsid formation.

  • N protein binds to nucleic acid at multiple sites in a coupled-allostery manner.

  • A RNP packaging model highlighting the importance of disorder and modularity is proposed.

Abstract

The nucleocapsid phosphoprotein of the severe acute respiratory syndrome coronavirus (SARS-CoV N protein) packages the viral genome into a helical ribonucleocapsid (RNP) and plays a fundamental role during viral self-assembly. It is a protein with multifarious activities. In this article we will review our current understanding of the N protein structure and its interaction with nucleic acid. Highlights of the progresses include uncovering the modular organization, determining the structures of the structural domains, realizing the roles of protein disorder in protein–protein and protein–nucleic acid interactions, and visualizing the ribonucleoprotein (RNP) structure inside the virions. It was also demonstrated that N-protein binds to nucleic acid at multiple sites with a coupled-allostery manner. We propose a SARS-CoV RNP model that conforms to existing data and bears resemblance to the existing RNP structures of RNA viruses. The model highlights the critical role of modular organization and intrinsic disorder of the N protein in the formation and functions of the dynamic RNP capsid in RNA viruses. This paper forms part of a symposium in Antiviral Research on “From SARS to MERS: 10 years of research on highly pathogenic human coronaviruses.”

Abbreviations

CTD
the C-terminal domain of N protein (a.a. 248–365)
DD
the di-domain comprising NTD, LKR and CTD (a.a. 45–365)
HCoV
human coronavirus
IDP
intrinsically disordered protein
IDR
intrinsically disordered region
LKR
the linker region of SARS-CoV N protein (a.a. 182–247)
N
nucleocapsid protein
NTD
the N-terminal domain of N protein (a.a. 45–181)
MHV
mouse hepatitis virus
RMSD
root mean square deviation
RNP
ribonucleoprotein
SARS-CoV
severe acute respiratory syndrome coronavirus

Keywords

SARS
Coronavirus
Nucleocapsid protein
Capsid packaging
Intrinsic disorder
RNP

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