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Three-dimensional structure of physalis mottle virus: implications for the viral assembly
S S Krishna1, C N Hiremath, S K Munshi
1Molecular Biophysics Unit, Indian Institute of Science Bangalore, 560 012, India. mrn@mbu.iisc.ernet.in
Journal of Molecular Biology
|June 17, 1999
Summary
The structure of physalis mottle virus (PhMV), a single-stranded RNA tymovirus, was determined at 3.8 Å resolution. This reveals distinct N-terminal arm conformations in its coat protein, suggesting a mechanism for empty capsid formation.
Area of Science:
- Structural biology
- Virology
- Biochemistry
Background:
- Physalis mottle virus (PhMV) is a T=3 single-stranded RNA tymovirus.
- Understanding viral capsid structure is crucial for virology and drug development.
Purpose of the Study:
- To determine the high-resolution structure of the PhMV capsid.
- To elucidate the structural basis for PhMV assembly and its relationship to other viruses.
Main Methods:
- X-ray crystallography at 3.8 Å resolution.
- Molecular replacement using Turnip yellow mosaic virus (TYMV) coordinates.
- Phase refinement and electron density map analysis.
Main Results:
- The PhMV capsid structure reveals a T=3 icosahedral arrangement.
- Distinct conformations of N-terminal arms in A subunits compared to B and C subunits were observed.
- Analysis of inter-subunit contacts suggests a mechanism for empty capsid formation.
- Comparison with Sesbania mosaic virus shows conserved tertiary folds despite different capsid morphologies.
Conclusions:
- The PhMV structure provides insights into viral capsid assembly and evolution.
- The findings offer a potential mechanism for the formation of empty viral capsids.
- Structural similarities with sobemoviruses highlight conserved features in plant virus coat proteins.