title: Virus DNA translocation: progress towards a first ascent of mount pretty difficult.
abstract: Virion DNA molecules of large dsDNA viruses are highly condensed. To pack the DNA, an ATP hydrolysis-powered motor translocates the DNA into a preformed empty protein shell, the prohead. The icosahedral prohead has a special fivefold vertex, the portal vertex, where the translocation machinery acts. The portal vertex contains the portal protein, a gear-shaped dodecamer of radially disposed subunits with a central channel for DNA entry. The symmetry mismatch between the fivefold symmetry of the shell vertex and the 12-fold symmetry of the portal protein has prompted DNA packaging models in which ATP-driven portal protein rotation drives DNA translocation. In this issue of Molecular Microbiology, Baumann and colleagues test portal rotation models using bacteriophage T4. A fusion between the gp20 portal protein and the HOC external shell decoration protein is used to create a block to portal rotation. Finding that DNA packaging is unimpeded in proheads containing the fusion argues that portal rotation is not crucial to DNA translocation. The paper is a landmark for describing direct testing of the mechanism of DNA translocation.
authors.affiliation: Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: Nasib K
authors.initials: NK
authors.lastname: Maluf
authors.forename: Michael
authors.initials: M
authors.lastname: Feiss
mesh_terms: D017122:Bacteriophage T4 / Q000235:genetics / Q000502:physiology*; D002213:Capsid / Q000378:metabolism; D036022:Capsid Proteins / Q000235:genetics / Q000378:metabolism; D042003:DNA Packaging / Q000235:genetics*; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D019065:Virus Assembly / Q000235:genetics / Q000502:physiology
chemical_list: D036022:Capsid Proteins; D004279:DNA, Viral; D014764:Viral Proteins; C119911:portal protein, Bacteriophage T4