8T1X

T4 highly immunogenic outer capsid protein C-terminal domain bound to the vertex-proximal gp23* capsomer of the isometric head in two preferred orientations

Summary for 8T1X

• Entry DOI: 10.2210/pdb8t1x/pdb
• EMDB information: 8661
• Descriptor: Highly immunogenic outer capsid protein, Mature major capsid protein gp23* (2 entities in total)
• Functional Keywords: bacteriophage, capsid, t4 head, hoc, highly immunogenic outer capsid protein, virus decoration protein, immunoglobulin-like domains, antigen display, vaccine, viral protein
• Biological source: Escherichia phage T4; More
• Total number of polymer chains: 8
• Total formula weight: 373206.27

Authors

Fokine, A.,Rao, V.B. (deposition date: 2023-06-04, release date: 2023-07-19, Last modification date: 2024-06-19)

Primary citation

Fokine, A.,Islam, M.Z.,Fang, Q.,Chen, Z.,Sun, L.,Rao, V.B.
Structure and Function of Hoc-A Novel Environment Sensing Device Encoded by T4 and Other Bacteriophages.
Viruses, 15:-, 2023

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-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.

PubMed: 37515203
DOI: 10.3390/v15071517

Experimental method

ELECTRON MICROSCOPY (3.3 Å)