title: The T7 ejection nanomachine components gp15-gp16 form a spiral ring complex that binds DNA and a lipid membrane.
abstract: Bacteriophage T7 initiates infection by ejecting several internal capsid proteins into the host cell; these proteins then assemble into a nanomachine that translocates the viral genome from the phage head into the cytoplasm. The ejected proteins are thought to partially unfold as they pass through the lumen of the portal and the short stubby T7 tail during their entry into the cell. In vivo, the internal proteins gp15 and gp16 assemble into a tubular structure that spans the periplasm and cytoplasmic membrane. We show here that purified gp15 and gp16 can refold from a partially denatured state in vitro, and that gp15 interacts with gp16 to form a spiral ring structure. Purified gp15 binds to DNA, whereas gp16 binds protein-free liposomes; the gp15-gp16 complex binds both DNA and liposomes. Limited proteolysis of the liposome-bound gp16 reveals that its C-terminal region is protected, suggesting a partial membrane insertion of the protein.
authors.affiliation: Institute of Microbiology and Molecular Biology, University of Hohenheim, 70599 Stuttgart, Germany.
authors.forename: Domenico
authors.initials: D
authors.lastname: Lupo
authors.affiliation: Institute of Microbiology and Molecular Biology, University of Hohenheim, 70599 Stuttgart, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Leptihn
authors.affiliation: Institute of Microbiology and Molecular Biology, University of Hohenheim, 70599 Stuttgart, Germany.
authors.forename: Gisela
authors.initials: G
authors.lastname: Nagler
authors.affiliation: Institute of Microbiology and Molecular Biology, University of Hohenheim, 70599 Stuttgart, Germany.
authors.forename: Maximillian
authors.initials: M
authors.lastname: Haase
authors.affiliation: Center for Infectious Disease, Department of Molecular Biosciences, Institute for Cell and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Ian
authors.initials: I
authors.lastname: J Molineux
authors.affiliation: Institute of Microbiology and Molecular Biology, University of Hohenheim, 70599 Stuttgart, Germany. Electronic address: andikuhn@uni-hohenheim.de.
authors.forename: Andreas
authors.initials: A
authors.lastname: Kuhn
mesh_terms: D017123:Bacteriophage T7 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism / Q000821:virology*; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism / Q000821:virology*; D008563:Membrane Lipids / Q000235:genetics / Q000378:metabolism*; D014758:Viral Core Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D004279:DNA, Viral; D008563:Membrane Lipids; D014758:Viral Core Proteins; C412714:gene16 product, bacteriophage T7
keywords: Bacteriophage T7; DNA ejection; Penetration; gp15–gp16 structure