Journal: Proc Natl Acad Sci U S A / Year: 2015 Title: Structural remodeling of bacteriophage T4 and host membranes during infection initiation. Authors: Bo Hu / William Margolin / Ian J Molineux / Jun Liu / Abstract: The first stages of productive bacteriophage infections of bacterial host cells require efficient adsorption to the cell surface followed by ejection of phage DNA into the host cytoplasm. To achieve ...The first stages of productive bacteriophage infections of bacterial host cells require efficient adsorption to the cell surface followed by ejection of phage DNA into the host cytoplasm. To achieve this goal, a phage virion must undergo significant structural remodeling. For phage T4, the most obvious change is the contraction of its tail. Here, we use skinny E. coli minicells as a host, along with cryo-electron tomography and mutant phage virions, to visualize key structural intermediates during initiation of T4 infection. We show for the first time that most long tail fibers are folded back against the tail sheath until irreversible adsorption, a feature compatible with the virion randomly walking across the cell surface to find an optimal site for infection. Our data confirm that tail contraction is triggered by structural changes in the baseplate, as intermediates were found with remodeled baseplates and extended tails. After contraction, the tail tube penetrates the host cell periplasm, pausing while it degrades the peptidoglycan layer. Penetration into the host cytoplasm is accompanied by a dramatic local outward curvature of the cytoplasmic membrane as it fuses with the phage tail tip. The baseplate hub protein gp27 and/or the ejected tape measure protein gp29 likely form the transmembrane channel for viral DNA passage into the cell cytoplasm. Building on the wealth of prior biochemical and structural information, this work provides new molecular insights into the mechanistic pathway of T4 phage infection.
History
Deposition
Sep 1, 2014
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Header (metadata) release
Oct 8, 2014
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Map release
Aug 26, 2015
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Update
Sep 9, 2015
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Current status
Sep 9, 2015
Processing site: PDBe / Status: Released
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Structure visualization
Movie
Surface view with section colored by density value
Specimen holder: Nitrogen cooled / Specimen holder model: GATAN LIQUID NITROGEN / Tilt series - Axis1 - Min angle: -64 ° / Tilt series - Axis1 - Max angle: 64 °
Experimental equipment
Model: Tecnai Polara / Image courtesy: FEI Company
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Image processing
Details
The particles were manually selected from cryo-tomograms.
Final reconstruction
Applied symmetry - Point group: C1 (asymmetric) / Algorithm: OTHER / Resolution.type: BY AUTHOR / Resolution: 36.0 Å / Resolution method: OTHER / Software - Name: IMOD, Protomo, i3, EMAN / Number subtomograms used: 1958
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