The incorporation of reovirus cell attachment protein sigma 1 into virions requires the N-terminal hydrophobic tail and the adjacent heptad repeat region.
The N-terminal portion of the reovirus cell attachment protein sigma 1 has recently been shown to possess intrinsic oligomerization and virion-anchoring functions. Sequence analysis of the sigma 1 proteins of the three reovirus serotypes has revealed the presence of distinct structural domains within this region: a terminal hydrophobic tail, a hinge, and an extended coiled-coil. To probe the inter-relationship between the virion-anchoring function and the oligomerization function, we constructed two serotype 3 (T3) sigma 1 deletion mutants in SV40 expression vectors, one lacking the hydrophobic tail and the hinge, and the other lacking an adjacent region which constituted part of the coiled-coil. These mutants were (i) expressed in uninfected COS-1 cells and assayed for their ability to form oligomers, and (ii) expressed in type 1 (T1) reovirus-infected COS-1 cells and assayed for their incorporability into progeny T1 virions. It was found that, whereas both truncated sigma 1 proteins were capable of forming stable oligomers, neither could be incorporated into virions. These observations, coupled with structural characteristics deduced from sequence analysis, are compatible with a model in which the hydrophobic tail is the bona fide sigma 1 anchorage domain and whose precise association with the virion spikes is dictated by an adjacent heptad repeat region linked to the former structure via a flexible hinge region.
Leone
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Department of Microbiology and Infectious Diseases, University of Calgary Health Sciences Centre, Alberta, Canada.
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D000595:Amino Acid Sequence; D000818:Animals; D036022:Capsid Proteins; D002460:Cell Line; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D004252:DNA Mutational Analysis; D008969:Molecular Sequence Data; D009024:Morphogenesis; D011485:Protein Binding; D012087:Reoviridae / Q000648:ultrastructure*; D015183:Restriction Mapping; D012995:Solubility; D013329:Structure-Activity Relationship; D014764:Viral Proteins / Q000737:chemistry / Q000378:metabolism*; D014771:Virion / Q000648:ultrastructure; D014779:Virus Replication
D036022:Capsid Proteins; D014764:Viral Proteins; C031728:sigma 1 protein, reovirus