title: Role of bacteriophage T4 baseplate in regulating assembly and infection.
abstract: Bacteriophage T4 consists of a head for protecting its genome and a sheathed tail for inserting its genome into a host. The tail terminates with a multiprotein baseplate that changes its conformation from a "high-energy" dome-shaped to a "low-energy" star-shaped structure during infection. Although these two structures represent different minima in the total energy landscape of the baseplate assembly, as the dome-shaped structure readily changes to the star-shaped structure when the virus infects a host bacterium, the dome-shaped structure must have more energy than the star-shaped structure. Here we describe the electron microscopy structure of a 3.3-MDa in vitro-assembled star-shaped baseplate with a resolution of 3.8 Å. This structure, together with other genetic and structural data, shows why the high-energy baseplate is formed in the presence of the central hub and how the baseplate changes to the low-energy structure, via two steps during infection. Thus, the presence of the central hub is required to initiate the assembly of metastable, high-energy structures. If the high-energy structure is formed and stabilized faster than the low-energy structure, there will be insufficient components to assemble the low-energy structure.
authors.affiliation: Department of Biological Sciences, Purdue University, West Lafayette, IN 47907;
authors.forename: Moh Lan
authors.initials: ML
authors.lastname: Yap
authors.affiliation: Department of Biological Sciences, Purdue University, West Lafayette, IN 47907;
authors.forename: Thomas
authors.initials: T
authors.lastname: Klose
authors.affiliation: College of Bioresource Science, Nihon University, Fujisawa, Kanagawa 252-0880, Japan;
authors.forename: Fumio
authors.initials: F
authors.lastname: Arisaka
authors.affiliation: National Resource for Automated Molecular Microscopy, The Scripps Research Institute, La Jolla, CA 92037;
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Speir
authors.affiliation: National Resource for Automated Molecular Microscopy, The Scripps Research Institute, La Jolla, CA 92037; Department of Biochemistry, University of Washington, Seattle, WA 98195.
authors.forename: David
authors.initials: D
authors.lastname: Veesler
authors.affiliation: Department of Biological Sciences, Purdue University, West Lafayette, IN 47907;
authors.forename: Andrei
authors.initials: A
authors.lastname: Fokine
authors.affiliation: Department of Biological Sciences, Purdue University, West Lafayette, IN 47907; mr@purdue.edu.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Rossmann
mesh_terms: D001419:Bacteria / Q000821:virology; D017122:Bacteriophage T4 / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure*; D020285:Cryoelectron Microscopy / Q000379:methods*; D018360:Crystallography, X-Ray; D007700:Kinetics; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D014743:Videotape Recording; D014764:Viral Proteins / Q000737:chemistry / Q000648:ultrastructure; D014771:Virion / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure*; D019065:Virus Assembly
chemical_list: D014764:Viral Proteins
keywords: bacteriophage T4; baseplate assembly; conformational changes; cryo-EM reconstruction; near-atomic resolution