T4 highly immunogenic outer capsid protein C-terminal domain bound to a vertex-proximal gp23* capsomer of the prolate capsid in two preferred orientations.
Components
Highly immunogenic outer capsid protein
Mature major capsid protein
Keywords
VIRAL PROTEIN / bacteriophage / capsid / T4 head / Hoc / highly immunogenic outer capsid protein / virus decoration protein / immunoglobulin-like domains / antigen display / vaccine
National Institutes of Health/National Institute Of Allergy and Infectious Diseases (NIH/NIAID)
United States
Citation
Journal: Viruses / Year: 2023 Title: Structure and Function of Hoc-A Novel Environment Sensing Device Encoded by T4 and Other Bacteriophages. Authors: Andrei Fokine / Mohammad Zahidul Islam / Qianglin Fang / Zhenguo Chen / Lei Sun / Venigalla B Rao / Abstract: Bacteriophage T4 is decorated with 155 180 Å-long fibers of the highly antigenic outer capsid protein (Hoc). In this study, we describe a near-atomic structural model of Hoc by combining cryo- ...Bacteriophage T4 is decorated with 155 180 Å-long fibers of the highly antigenic outer capsid protein (Hoc). In this study, we describe a near-atomic structural model of Hoc by combining cryo-electron microscopy and AlphaFold structure predictions. It consists of a conserved C-terminal capsid-binding domain attached to a string of three variable immunoglobulin (Ig)-like domains, an architecture well-preserved in hundreds of Hoc molecules found in phage genomes. Each T4-Hoc fiber attaches randomly to the center of gp23* hexameric capsomers in one of the six possible orientations, though at the vertex-proximal hexamers that deviate from 6-fold symmetry, Hoc binds in two preferred orientations related by 180° rotation. Remarkably, each Hoc fiber binds to all six subunits of the capsomer, though the interactions are greatest with three of the subunits, resulting in the off-centered attachment of the C-domain. Biochemical analyses suggest that the acidic Hoc fiber (pI, ~4-5) allows for the clustering of virions in acidic pH and dispersion in neutral/alkaline pH. Hoc appears to have evolved as a sensing device that allows the phage to navigate its movements through reversible clustering-dispersion transitions so that it reaches its destination, the host bacterium, and persists in various ecological niches such as the human/mammalian gut.
#221 - May 2018 Human Papillomavirus and Vaccines similarity (1)
#200 - Aug 2016 Quasisymmetry in Icosahedral Viruses similarity (1)
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Assembly
Deposited unit
X: Highly immunogenic outer capsid protein Y: Highly immunogenic outer capsid protein A: Mature major capsid protein B: Mature major capsid protein C: Mature major capsid protein D: Mature major capsid protein E: Mature major capsid protein F: Mature major capsid protein
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