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Published on: October 14, 2011
Determinants of bacteriophage phi29 head morphology
Kyung H Choi1, Marc C Morais, Dwight L Anderson
1Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, Indiana 47907.
Structure (London, England : 1993)
|November 14, 2006
Summary
Bacteriophage phi29 scaffolding protein is essential for forming prolate capsids. Without it, isometric capsids assemble, revealing the protein
Area of Science:
- Structural biology
- Virology
- Biochemistry
Background:
- Bacteriophage phi29 prohead assembly relies on scaffolding protein.
- Proper assembly results in a 450 x 540 Å prolate structure with T=3 symmetry.
- Scaffolding protein's role in capsid symmetry and morphology is not fully understood.
Purpose of the Study:
- To investigate the role of scaffolding protein in bacteriophage phi29 capsid assembly.
- To characterize the structures formed in the absence of functional scaffolding protein.
- To elucidate the mechanism by which scaffolding protein influences capsid symmetry.
Main Methods:
- Cryo-electron microscopy was used to analyze capsid structures.
- Analysis of temperature-sensitive scaffolding protein mutants in bacteriophage phi29 infections.
- Comparative structural analysis of assembled procapsids and mature capsids.
Main Results:
- Absence of functional scaffolding protein leads to predominantly 370 Å isometric T=3 capsids lacking head-tail connectors.
- A subset of larger, 430 Å diameter, T=4 icosahedral particles are also observed.
- Both prolate and isometric capsids utilize similar pentamers and differentially skewed hexamers.
Conclusions:
- Scaffolding protein is crucial for the formation of the T=3 prolate phi29 prohead.
- The absence of scaffolding protein allows for the assembly of T=3 and T=4 isometric capsids.
- Hexamers exhibit differential skewing based on their environment, suggesting a role for scaffolding protein in stabilizing these conformations during assembly.
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