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Title | Structure and Function of Hoc-A Novel Environment Sensing Device Encoded by T4 and Other Bacteriophages. |
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Journal, issue, pages | Viruses, Vol. 15, Issue 7, Year 2023 |
Publish date | Jul 7, 2023 |
Authors | Andrei Fokine / Mohammad Zahidul Islam / Qianglin Fang / Zhenguo Chen / Lei Sun / Venigalla B Rao / |
PubMed 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. |
External links | Viruses / PubMed:37515203 / PubMed Central |
Methods | EM (single particle) |
Resolution | 3.3 - 3.4 Å |
Structure data | PDB-8t1x: PDB-8t9r: |
Source |
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Keywords | VIRAL PROTEIN / bacteriophage / capsid / T4 head / Hoc / highly immunogenic outer capsid protein / virus decoration protein / immunoglobulin-like domains / antigen display / vaccine |