Structural changes of bacteriophage phi29 upon DNA packaging and release.

Area of Science:

• Structural biology
• Virology
• Molecular biology

Background:

• Bacteriophage phi29 is a model system for studying viral assembly and infection.
• Understanding the structure of phi29 is crucial for deciphering its biological functions.

Purpose of the Study:

• To determine the high-resolution three-dimensional structure of mature and emptied bacteriophage phi29 particles.
• To elucidate the conformational changes involved in phi29 assembly and infection.
• To investigate the structure and orientation of phi29 appendages and their role in infection.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was used to generate 3D reconstructions of bacteriophage phi29 particles.
• No symmetry assumptions were made during the reconstruction process.
• Structural comparisons were made between mature, emptied, and prohead phi29 particles.

Main Results:

• High-resolution 3D structures of mature and emptied phi29 particles were obtained without symmetry constraints.
• The 12 appendages of phi29 were found to be homologous to bacteriophage P22 tailspikes.
• Appendage orientation and head fiber arrangement suggest a mechanism for host cell wall digestion during infection.
• The head-tail connector expands in the mature virus, with gene product 3 potentially facilitating DNA release and tail attachment.

Conclusions:

• Conformational changes in phi29 are key to its assembly and infection processes.
• The structure of phi29 appendages and their arrangement provide insights into the initial stages of infection.
• The expanded head-tail connector and gene product 3 play critical roles in DNA packaging and viral attachment.