title: Icosahedral bacteriophage ΦX174 forms a tail for DNA transport during infection.
abstract: Prokaryotic viruses have evolved various mechanisms to transport their genomes across bacterial cell walls. Many bacteriophages use a tail to perform this function, whereas tail-less phages rely on host organelles. However, the tail-less, icosahedral, single-stranded DNA ΦX174-like coliphages do not fall into these well-defined infection processes. For these phages, DNA delivery requires a DNA pilot protein. Here we show that the ΦX174 pilot protein H oligomerizes to form a tube whose function is most probably to deliver the DNA genome across the host's periplasmic space to the cytoplasm. The 2.4 Å resolution crystal structure of the in vitro assembled H protein's central domain consists of a 170 Å-long α-helical barrel. The tube is constructed of ten α-helices with their amino termini arrayed in a right-handed super-helical coiled-coil and their carboxy termini arrayed in a left-handed super-helical coiled-coil. Genetic and biochemical studies demonstrate that the tube is essential for infectivity but does not affect in vivo virus assembly. Cryo-electron tomograms show that tubes span the periplasmic space and are present while the genome is being delivered into the host cell's cytoplasm. Both ends of the H protein contain transmembrane domains, which anchor the assembled tubes into the inner and outer cell membranes. The central channel of the H-protein tube is lined with amide and guanidinium side chains. This may be a general property of viral DNA conduits and is likely to be critical for efficient genome translocation into the host.
authors: 1] Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA [2].
authors: Lei
authors: L
authors: Sun
authors: 1] School of Plant Sciences and the BIO5 Institute, University of Arizona, Tucson, Arizona 85721, USA [2].
authors: Lindsey N
authors: LN
authors: Young
authors: 1] Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA [2].
authors: Xinzheng
authors: X
authors: Zhang
authors: 1] Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA [2] The Research Department, Shriner's Hospital for Children, Portland, Oregon 97239, USA.
authors: Sergei P
authors: SP
authors: Boudko
authors: Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
authors: Andrei
authors: A
authors: Fokine
authors: Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
authors: Erica
authors: E
authors: Zbornik
authors: School of Plant Sciences and the BIO5 Institute, University of Arizona, Tucson, Arizona 85721, USA.
authors: Aaron P
authors: AP
authors: Roznowski
authors: Molecular Genetics and Microbiology, Institute for Cell and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA.
authors: Ian J
authors: IJ
authors: Molineux
authors: Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
authors: Michael G
authors: MG
authors: Rossmann
authors: School of Plant Sciences and the BIO5 Institute, University of Arizona, Tucson, Arizona 85721, USA.
authors: Bentley A
authors: BA
authors: Fane
mesh_terms: D010584:Bacteriophage phi X 174 / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D001692:Biological Transport; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D003593:Cytoplasm / Q000378:metabolism / Q000648:ultrastructure / Q000821:virology; D004279:DNA, Viral / Q000378:metabolism* / Q000648:ultrastructure; D004926:Escherichia coli / Q000166:cytology / Q000648:ultrastructure / Q000821:virology*; D016679:Genome, Viral; D008958:Models, Molecular; D019897:Periplasm / Q000378:metabolism / Q000648:ultrastructure; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D014764:Viral Proteins / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D019065:Virus Assembly
chemical_list: D004279:DNA, Viral; D014764:Viral Proteins