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Association of reovirus outer capsid proteins sigma 3 and mu 1 causes a conformational change that renders sigma 3
D A Shepard1, J G Ehnstrom, L A Schiff
1Department of Microbiology, University of Minnesota, Minneapolis 55455, USA.
Abstract:
Association of the reovirus proteins sigma 3 and mu 1 influences viral entry, initiation of outer capsid assembly, and modulation of the effect of sigma 3 on cellular translation. In this study, we have addressed whether structural changes occur in sigma 3 as a result of its interaction with mu 1. Using differences in protease sensitivity to detect conformationally distinct forms of sigma 3, we showed that association of sigma 3 with mu 1 caused a conformational change in sigma 3 that converted it from a protease-resistant to a protease-sensitive structure and occurred posttranslationally. The effect of mu 1 on the structure of sigma 3 was stoichiometric. Our results are consistent with a model in which sigma 3's association with mu 1 shifts its function from translational control to assembly of an outer capsid in which sigma 3 is folded into the protease-sensitive conformation that is required for its cleavage during the next round of infection.
Insights
Reovirus proteins sigma 3 and mu 1 interact, causing a structural change in sigma 3. This conformational shift is crucial for viral assembly and function during infection.
Area of Science:
- Virology
- Molecular Biology
- Structural Biology
Background:
- Reovirus protein interactions are key to viral replication.
- Sigma 3 protein regulates cellular translation and outer capsid assembly.
- Mu 1 protein's role in sigma 3's function is not fully understood.
Purpose of the Study:
- To investigate structural changes in reovirus sigma 3 protein upon association with mu 1.
- To determine if mu 1 binding induces conformational alterations in sigma 3.
Main Methods:
- Utilized protease sensitivity assays to differentiate conformational states of sigma 3.
- Analyzed the stoichiometric relationship between mu 1 and sigma 3 association.
Main Results:
- Association of sigma 3 with mu 1 induced a post-translational conformational change.
- Sigma 3 transitioned from a protease-resistant to a protease-sensitive state upon binding mu 1.
- The effect of mu 1 on sigma 3 structure was stoichiometric.
Conclusions:
- Mu 1 binding induces a conformational change in sigma 3, shifting its function.
- This conformational shift facilitates outer capsid assembly.
- The protease-sensitive conformation of sigma 3 is necessary for its cleavage in subsequent infection rounds.