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Structural studies of the giant mimivirus
Chuan Xiao1, Yurii G Kuznetsov, Siyang Sun
1Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America.
Plos Biology
|May 1, 2009
Summary
Mimivirus, the largest known virus, has a unique capsid structure with hexagonal depressions and a starfish-shaped feature that may regulate genome delivery. Its large size and complex structure suggest a hybrid genome.
Area of Science:
- Structural biology
- Virology
- Microbiology
Background:
- Mimivirus is the largest known virus, challenging the definition of viruses versus cells due to its size and genome.
- Previous structural studies were hindered by Mimivirus's size and extensive surface fibers.
Purpose of the Study:
- To elucidate the three-dimensional structure of the Mimivirus capsid.
- To investigate the function of the surface fibers and unique structural features.
Main Methods:
- Enzymatic digestion to remove surface fibers.
- Cryo-electron microscopy (cryoEM) for high-resolution imaging.
- Atomic force microscopy to analyze surface topography.
Main Results:
- Mimivirus capsids exhibit hexagonal arrays of depressions on their 20 icosahedral faces.
- Capsomers are arranged with unique orientations and vacancies, differing from other large viruses.
- A distinct starfish-shaped feature at a pentameric vertex acts as a seal, with an internally oriented nucleocapsid.
Conclusions:
- The unique capsid structure and nucleocapsid organization suggest a role in regulating viral genome delivery.
- Mimivirus's complex structure and fiber components indicate a genome with eukaryotic and prokaryotic origins.
- This study provides a high-resolution 3D reconstruction of an unprecedentedly large viral assembly.
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