Assembly of the reovirus outer capsid requires mu 1/sigma 3 interactions which are prevented by misfolded sigma 3 protein in temperature-sensitive mutant tsG453.
A temperature-sensitive reovirus mutant, tsG453, whose defect was mapped to major outer capsid protein sigma 3, makes core particles but fails to assemble the outer capsid around the core at non-permissive temperature. Previous studies that made use of electron cryo-microscopy and image reconstructions showed that mu 1, the other major outer capsid protein, but not sigma 3, interact extensively with the core capsid. Although wild-type sigma 3 and mu 1 interact with each other, immunocoprecipitation studies showed that mutant sigma 3 protein was incapable of interacting with mu 1 at the non-permissive temperature. In addition, restrictively-grown mutant sigma 3 protein could not be precipitated by some sigma 3-specific monoclonal antibodies. These observations suggest that in a wild-type infection, specific sigma 3 and mu 1 interactions result in changes in mu 1 conformation which are required to allow mu 1/sigma 3 complexes to condense onto the core capsid shell during outer capsid assembly, and that sigma 3 in non-permissive tsG453 infections is misfolded such that it cannot interact with mu 1.
Shing
M
M
Department of Medical Microbiology and Infectious Diseases, University of Manitoba, Winnipeg, Canada.
Coombs
K M
KM
D002213:Capsid / Q000096:biosynthesis / Q000378:metabolism*; D036022:Capsid Proteins; D005814:Genes, Viral; D009154:Mutation; D011487:Protein Conformation; D017510:Protein Folding; D016601:RNA-Binding Proteins; D012087:Reoviridae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D013696:Temperature; D014764:Viral Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D019065:Virus Assembly / Q000235:genetics*
D036022:Capsid Proteins; D016601:RNA-Binding Proteins; D014764:Viral Proteins; C055356:mu1 protein, Reovirus; C053179:sigma protein 3, Reovirus