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J Biol Chem. 2015 Apr 17;290(16):10038-44. doi: 10.1074/jbc.M114.614222. Epub 2015 Feb 19.

Conformational changes leading to T7 DNA delivery upon interaction with the bacterial receptor.

Author information

1
From the Structure of Macromolecules Department, Centro Nacional de Biotecnología (CSIC), Darwin 3, Cantoblanco, 28049 Madrid and.
2
From the Structure of Macromolecules Department, Centro Nacional de Biotecnología (CSIC), Darwin 3, Cantoblanco, 28049 Madrid and acuervo@cnb.csic.es.
3
From the Structure of Macromolecules Department, Centro Nacional de Biotecnología (CSIC), Darwin 3, Cantoblanco, 28049 Madrid and Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA Nanociencia), Cantoblanco, 28049 Madrid, Spain jlcarras@cnb.csic.es.

Abstract

The majority of bacteriophages protect their genetic material by packaging the nucleic acid in concentric layers to an almost crystalline concentration inside protein shells (capsid). This highly condensed genome also has to be efficiently injected into the host bacterium in a process named ejection. Most phages use a specialized complex (often a tail) to deliver the genome without disrupting cell integrity. Bacteriophage T7 belongs to the Podoviridae family and has a short, non-contractile tail formed by a tubular structure surrounded by fibers. Here we characterize the kinetics and structure of bacteriophage T7 DNA delivery process. We show that T7 recognizes lipopolysaccharides (LPS) from Escherichia coli rough strains through the fibers. Rough LPS acts as the main phage receptor and drives DNA ejection in vitro. The structural characterization of the phage tail after ejection using cryo-electron microscopy (cryo-EM) and single particle reconstruction methods revealed the major conformational changes needed for DNA delivery at low resolution. Interaction with the receptor causes fiber tilting and opening of the internal tail channel by untwisting the nozzle domain, allowing release of DNA and probably of the internal head proteins.

KEYWORDS:

Bacteriophage; DNA Viruses; Electron Microscopy (EM); Protein Complex; Virus Entry; Virus Structure

PMID:
25697363
PMCID:
PMC4400320
DOI:
10.1074/jbc.M114.614222
[Indexed for MEDLINE]
Free PMC Article

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