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Analysis of Group IV Viral SSHHPS Using In Vitro and In Silico Methods
Published on: December 21, 2019
Characterization and function of putative substrate specificity domain in microvirus external scaffolding proteins
Asako Uchiyama1, Min Chen, Bentley A Fane
1Department of Veterinary Sciences and Microbiology, University of Arizona, Tucson, AZ 85721-0090, USA.
Journal of Virology
|June 8, 2007
Summary
The external scaffolding protein D in microviruses is crucial for icosahedral shell formation. Alpha-helix 1 likely initiates the assembly process, with mutations improving efficiency by altering kinetics.
Area of Science:
- Virology
- Structural Biology
- Molecular Biology
Background:
- Microviruses, such as bacteriophage phiX174, are T=1 icosahedral viruses.
- Viral assembly relies on scaffolding proteins, with external scaffolding protein D being key for morphogenesis.
- Previous studies suggested alpha-helix 1 of protein D mediates initial interactions, but used non-physiological expression systems.
Purpose of the Study:
- To investigate the role of alpha-helix 1 in microvirus assembly under physiological conditions.
- To elucidate the mechanistic details of the initial scaffolding protein-coat protein interaction.
- To understand how mutations affect the kinetics of virion production.
Main Methods:
- A chimeric external scaffolding gene was integrated into the phiX174 genome under native control.
- Characterization of the resulting chimeric virus, which showed non-viability in plaque formation.
- Genetic and biochemical analyses of the chimeric virus and isolated mutants.
Main Results:
- Alpha-helix 1 of the external scaffolding protein D is implicated in nucleating the formation of the first assembly intermediate.
- The chimeric virus, despite non-viability, provided insights into early assembly steps.
- Second-site mutations were identified that enhance the utilization of the chimeric protein.
Conclusions:
- Alpha-helix 1 plays a critical role in the nucleation phase of microvirus assembly.
- Mutations affecting assembly kinetics can shorten the lag phase and potentially lower the required concentration of scaffolding protein.
- This study provides a more detailed mechanistic model for microvirus morphogenesis under physiological conditions.
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