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Bacteriophage phi29 scaffolding protein gp7 before and after prohead assembly
Marc C Morais1, Shuji Kanamaru, Mohammed O Badasso
1Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, Indiana 47907-2054, USA.
Nature Structural Biology
|June 5, 2003
Summary
The bacteriophage phi29 scaffolding protein (gp7) forms arrow-shaped dimers and binds DNA. This DNA binding may regulate the transition from prohead to mature virus and scaffold release.
Area of Science:
- Structural biology
- Virology
- Molecular biology
Background:
- The bacteriophage phi29 scaffolding protein, gp7, is essential for viral assembly.
- Understanding the structure and function of gp7 is crucial for deciphering viral morphogenesis.
Purpose of the Study:
- To determine the three-dimensional structures of gp7 before and after prohead assembly.
- To investigate the DNA-binding capabilities of gp7 and its potential role in viral assembly.
Main Methods:
- X-ray crystallography was used to determine the high-resolution structures of gp7.
- Native gel electrophoresis was employed to confirm DNA binding.
- Cryo-electron microscopy (cryo-EM) was utilized to analyze gp7 arrangement within the capsid.
Main Results:
- The structures of gp7 before and after prohead assembly were determined at 2.2 and 2.8 Å resolution, respectively.
- gp7 exists as arrow-shaped dimers, featuring a four-helix bundle and a coiled coil.
- gp7 demonstrated DNA-binding activity, similar to the yeast transcription factor GCN4.
- Cryo-EM revealed gp7 arranged in concentric shells within the capsid, potentially interacting with hexamers.
Conclusions:
- gp7's structure suggests a DNA-binding function, confirmed experimentally.
- DNA binding by gp7 may be involved in the structural transition during viral maturation and scaffold release.
- gp7's arrangement within the capsid indicates a regulatory role in prohead formation through interactions with hexamers.