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Following Cell-fate in E. coli After Infection by Phage Lambda
Published on: October 14, 2011
The holin of bacteriophage lambda forms rings with large diameter.
Molecular Microbiology
|September 13, 2008
Summary
Bacteriophage lambda holin (S105) forms large ring structures in vitro, revealing the physical basis of holin oligomerization. These structures mimic the lethal holes holins create to trigger phage lysis and end the infection cycle.
Area of Science:
- Microbiology
- Structural Biology
- Biophysics
Background:
- Holins are essential phage proteins that control lysis by forming pores in the bacterial membrane.
- The physical basis and structure of holin oligomers, crucial for membrane permeabilization, remain largely unknown.
Purpose of the Study:
- To characterize the in vitro structures formed by bacteriophage lambda holin (S105).
- To elucidate the physical basis of holin oligomerization and the structure of the resulting membrane pores.
Main Methods:
- Purification of bacteriophage lambda holin (S105).
- Electron microscopy and single-particle analysis of purified S105 in detergent solutions.
- Proteolysis and cysteine-specific modification assays on S105 structures and membrane vesicles.
Main Results:
- Purified S105 forms ring-like oligomers in vitro, with a common class of ~72 monomers, 8.5 nm inner diameter, 23 nm outer diameter, and 4 nm height.
- These ring structures are consistent with the thickness of the lipid bilayer.
- The large central channel of the S105 rings is consistent with non-specific membrane permeabilization.
- S105 rings and membrane-associated S105 show similar proteolysis and modification sensitivities.
Conclusions:
- The in vitro formed S105 rings represent the structure of the lethal holes responsible for phage lysis.
- This study provides the first structural insights into holin oligomerization and pore formation.
- Understanding holin structure is key to understanding the termination of the phage infection cycle.
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