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Proc Natl Acad Sci U S A. 2016 Mar 8;113(10):2654-9. doi: 10.1073/pnas.1601654113. Epub 2016 Feb 29.

Role of bacteriophage T4 baseplate in regulating assembly and infection.

Author information

1
Department of Biological Sciences, Purdue University, West Lafayette, IN 47907;
2
College of Bioresource Science, Nihon University, Fujisawa, Kanagawa 252-0880, Japan;
3
National Resource for Automated Molecular Microscopy, The Scripps Research Institute, La Jolla, CA 92037;
4
National Resource for Automated Molecular Microscopy, The Scripps Research Institute, La Jolla, CA 92037; Department of Biochemistry, University of Washington, Seattle, WA 98195.
5
Department of Biological Sciences, Purdue University, West Lafayette, IN 47907; mr@purdue.edu.

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.

KEYWORDS:

bacteriophage T4; baseplate assembly; conformational changes; cryo-EM reconstruction; near-atomic resolution

PMID:
26929357
PMCID:
PMC4791028
DOI:
10.1073/pnas.1601654113
[Indexed for MEDLINE]
Free PMC Article

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