Structure and Function Studies of the Nucleocapsid Protein of Mouse Hepatitis Virus
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Coronaviruses, like virtually all single-stranded RNA viruses, contain a nucleocapsid (N) protein in close structural association with their genomes.1 Knowledge of the structure and functions of N proteins would be fundamental to an understanding of the viral life cycle and pathogenesis. We have undertaken a study of the N protein of mouse hepatitis virus (MHV) in an attempt to learn the roles of this protein in viral assembly, transcription and translation. Specifically, we would like to examine: (i) the nature of the interaction between N protein and the genome RNA; (ii) the nature of the interactions between adjacent and more distant pairs of N monomers in the helically symmetric viral nucleocapsid; and (iii) the location and purpose of the phosphoserine residue(s) known to occur in the N molecule.2,3 To date, we have pursued three approaches to these questions: (i) a comparison of the sequences of the N proteins of different, independently isolated strains of MHV; (ii) the examination of an N protein mutant of MHV-A59, Albany-4; and (iii) the in vitro expression and functional assay of N protein and of engineered mutants of N protein. Our results suggest that the MHV N protein has three structural domains, at least two of which may be functionally distinct.
KeywordsInfectious Bronchitis Virus Nucleocapsid Protein Viral Life Cycle Nonpermissive Temperature Bromphenol Blue