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Cryo-EM structure of the bacteriophage T4 portal protein assembly at near-atomic resolution.

Sun L, Zhang X, Gao S, Rao PA, Padilla-Sanchez V, Chen Z, Sun S, Xiang Y, Subramaniam S, Rao VB, Rossmann MG - Nat Commun (2015)

Bottom Line: However, the detailed structure of the portal protein remained unknown.The gp20 structure also verifies that the portal assembly is required for initiating head assembly, for attachment of the packaging motor, and for participation in DNA packaging.Comparison of the Myoviridae T4 portal structure with the known portal structures of φ29, SPP1 and P22, representing Podo- and Siphoviridae, shows that the portal structure probably dates back to a time when self-replicating microorganisms were being established on Earth.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Purdue University, 240S. Martin Jischke Drive, West Lafayette, Indiana 47907-2032, USA.

ABSTRACT
The structure and assembly of bacteriophage T4 has been extensively studied. However, the detailed structure of the portal protein remained unknown. Here we report the structure of the bacteriophage T4 portal assembly, gene product 20 (gp20), determined by cryo-electron microscopy (cryo-EM) to 3.6 Å resolution. In addition, analysis of a 10 Å resolution cryo-EM map of an empty prolate T4 head shows how the dodecameric portal assembly interacts with the capsid protein gp23 at the special pentameric vertex. The gp20 structure also verifies that the portal assembly is required for initiating head assembly, for attachment of the packaging motor, and for participation in DNA packaging. Comparison of the Myoviridae T4 portal structure with the known portal structures of φ29, SPP1 and P22, representing Podo- and Siphoviridae, shows that the portal structure probably dates back to a time when self-replicating microorganisms were being established on Earth.

No MeSH data available.


Related in: MedlinePlus

Comparison of the four known portal proteins.The upper row (a–d) shows the different portal protein subunits with their wing, stem, clip and crown domains coloured green, blue, purple and orange, respectively (PDB IDs of portals: φ29: 1FOU, SPP1: 2JES, P22: 3LJ4). The lower row (e–h) shows the portal assemblies docked into their respective phage capsids (cyan). The T4 portal structure was fitted into the 10 Å resolution EM map of the prolate head. Similarly the other portal structures were docked into their capsid structures (PDB IDs: φ29: 1YXN, P22: 2XYZ, SPP1: 4AN5).
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f4: Comparison of the four known portal proteins.The upper row (a–d) shows the different portal protein subunits with their wing, stem, clip and crown domains coloured green, blue, purple and orange, respectively (PDB IDs of portals: φ29: 1FOU, SPP1: 2JES, P22: 3LJ4). The lower row (e–h) shows the portal assemblies docked into their respective phage capsids (cyan). The T4 portal structure was fitted into the 10 Å resolution EM map of the prolate head. Similarly the other portal structures were docked into their capsid structures (PDB IDs: φ29: 1YXN, P22: 2XYZ, SPP1: 4AN5).

Mentions: The T4 portal model is missing the first 73 residues. However, there is no extra density in the 10 Å resolution prolate prohead cryo-EM reconstruction that might account for these missing residues, suggesting that these residues are disordered. The only available space for these residues appears to be the ‘empty' region between the external surface of the portal and the internal surface of the tube or the hole formed by the capsid, created by the absence of the gp24 vertex protein (Fig. 3c,d). Therefore, it is perhaps reasonable to place these residues snuggly around the outer surface of the portal, as a part of the wing domain, similar to the other portal structures (Fig. 3e and Fig. 4). In addition, this would leave the wing domains accessible to bind gp23 hexamers, initiating further hexamer binding until the complete head has been formed (Fig. 3e), consistent with the expectation that the portal is required to initiate head assembly3. Indeed, mutational analysis shows that deletion of the N-terminal region inhibits the head assembly (Supplementary Table 1).


Cryo-EM structure of the bacteriophage T4 portal protein assembly at near-atomic resolution.

Sun L, Zhang X, Gao S, Rao PA, Padilla-Sanchez V, Chen Z, Sun S, Xiang Y, Subramaniam S, Rao VB, Rossmann MG - Nat Commun (2015)

Comparison of the four known portal proteins.The upper row (a–d) shows the different portal protein subunits with their wing, stem, clip and crown domains coloured green, blue, purple and orange, respectively (PDB IDs of portals: φ29: 1FOU, SPP1: 2JES, P22: 3LJ4). The lower row (e–h) shows the portal assemblies docked into their respective phage capsids (cyan). The T4 portal structure was fitted into the 10 Å resolution EM map of the prolate head. Similarly the other portal structures were docked into their capsid structures (PDB IDs: φ29: 1YXN, P22: 2XYZ, SPP1: 4AN5).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493910&req=5

f4: Comparison of the four known portal proteins.The upper row (a–d) shows the different portal protein subunits with their wing, stem, clip and crown domains coloured green, blue, purple and orange, respectively (PDB IDs of portals: φ29: 1FOU, SPP1: 2JES, P22: 3LJ4). The lower row (e–h) shows the portal assemblies docked into their respective phage capsids (cyan). The T4 portal structure was fitted into the 10 Å resolution EM map of the prolate head. Similarly the other portal structures were docked into their capsid structures (PDB IDs: φ29: 1YXN, P22: 2XYZ, SPP1: 4AN5).
Mentions: The T4 portal model is missing the first 73 residues. However, there is no extra density in the 10 Å resolution prolate prohead cryo-EM reconstruction that might account for these missing residues, suggesting that these residues are disordered. The only available space for these residues appears to be the ‘empty' region between the external surface of the portal and the internal surface of the tube or the hole formed by the capsid, created by the absence of the gp24 vertex protein (Fig. 3c,d). Therefore, it is perhaps reasonable to place these residues snuggly around the outer surface of the portal, as a part of the wing domain, similar to the other portal structures (Fig. 3e and Fig. 4). In addition, this would leave the wing domains accessible to bind gp23 hexamers, initiating further hexamer binding until the complete head has been formed (Fig. 3e), consistent with the expectation that the portal is required to initiate head assembly3. Indeed, mutational analysis shows that deletion of the N-terminal region inhibits the head assembly (Supplementary Table 1).

Bottom Line: However, the detailed structure of the portal protein remained unknown.The gp20 structure also verifies that the portal assembly is required for initiating head assembly, for attachment of the packaging motor, and for participation in DNA packaging.Comparison of the Myoviridae T4 portal structure with the known portal structures of φ29, SPP1 and P22, representing Podo- and Siphoviridae, shows that the portal structure probably dates back to a time when self-replicating microorganisms were being established on Earth.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Purdue University, 240S. Martin Jischke Drive, West Lafayette, Indiana 47907-2032, USA.

ABSTRACT
The structure and assembly of bacteriophage T4 has been extensively studied. However, the detailed structure of the portal protein remained unknown. Here we report the structure of the bacteriophage T4 portal assembly, gene product 20 (gp20), determined by cryo-electron microscopy (cryo-EM) to 3.6 Å resolution. In addition, analysis of a 10 Å resolution cryo-EM map of an empty prolate T4 head shows how the dodecameric portal assembly interacts with the capsid protein gp23 at the special pentameric vertex. The gp20 structure also verifies that the portal assembly is required for initiating head assembly, for attachment of the packaging motor, and for participation in DNA packaging. Comparison of the Myoviridae T4 portal structure with the known portal structures of φ29, SPP1 and P22, representing Podo- and Siphoviridae, shows that the portal structure probably dates back to a time when self-replicating microorganisms were being established on Earth.

No MeSH data available.


Related in: MedlinePlus