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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.


The structure of gp20.(a) Charge distribution on the outer surface of dodecameric gp20. Blue and red colours correspond to 10 kT e− positive and negative potential, respectively. (b) Charge distribution on the inner surface of dodecameric gp20. (c) Ribbon drawing of the gp20 monomer structure with each domain colour-coded.
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f2: The structure of gp20.(a) Charge distribution on the outer surface of dodecameric gp20. Blue and red colours correspond to 10 kT e− positive and negative potential, respectively. (b) Charge distribution on the inner surface of dodecameric gp20. (c) Ribbon drawing of the gp20 monomer structure with each domain colour-coded.

Mentions: The T4 portal protein assembly is dodecameric and has a length of ∼120 Å (Fig. 1). The external diameter of the portal complex varies from 90 Å at the ‘upper' end to 170 Å in the middle and to 80 Å at the ‘lower' end close to the outside the capsid. The central channel has a diameter of about 44 Å at the upper end, decreasing to 28 Å at the narrowest point near the middle of the cylinder (Fig. 2b). The crown domain (residues 451–524) consists of three α-helices (α10, α11 and α12) connected by short turns and eight additional disordered C-terminal residues (Fig. 2c). The wing domain (residues 70–254 and 378–450) consists of α-helices α1, α2, α3, α4, α8 and α9 and forms the central part of the portal assembly. A bent helix, α8, is 30-residues long (residues 399–428) and is connected to the stem region (residues 255–278 and 359–377) by the ‘tunnel' loop (residues 374–398). This loop protrudes into the central channel of the portal assembly and has lower density than the rest of the structure, suggesting flexibility. In the portal structures of the SPP1, P22 and φ29 this loop is 14, 10 and 23 amino-acid long, respectively, and is mostly completely disordered. The stem region consists of two helices, α5 and α7, that are oriented at an angle of about 40° with respect to the central 12-fold axis and are connected to each other by the clip domain. The clip domain (residues 279–358) consists of three β-strands and helix α6. This domain is exposed on the outside of the capsid. It is the site of attachment of the packaging ATPase, gp17, during DNA packaging, as well as for attachment of the neck (gp13) and tail in the mature phage.


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)

The structure of gp20.(a) Charge distribution on the outer surface of dodecameric gp20. Blue and red colours correspond to 10 kT e− positive and negative potential, respectively. (b) Charge distribution on the inner surface of dodecameric gp20. (c) Ribbon drawing of the gp20 monomer structure with each domain colour-coded.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: The structure of gp20.(a) Charge distribution on the outer surface of dodecameric gp20. Blue and red colours correspond to 10 kT e− positive and negative potential, respectively. (b) Charge distribution on the inner surface of dodecameric gp20. (c) Ribbon drawing of the gp20 monomer structure with each domain colour-coded.
Mentions: The T4 portal protein assembly is dodecameric and has a length of ∼120 Å (Fig. 1). The external diameter of the portal complex varies from 90 Å at the ‘upper' end to 170 Å in the middle and to 80 Å at the ‘lower' end close to the outside the capsid. The central channel has a diameter of about 44 Å at the upper end, decreasing to 28 Å at the narrowest point near the middle of the cylinder (Fig. 2b). The crown domain (residues 451–524) consists of three α-helices (α10, α11 and α12) connected by short turns and eight additional disordered C-terminal residues (Fig. 2c). The wing domain (residues 70–254 and 378–450) consists of α-helices α1, α2, α3, α4, α8 and α9 and forms the central part of the portal assembly. A bent helix, α8, is 30-residues long (residues 399–428) and is connected to the stem region (residues 255–278 and 359–377) by the ‘tunnel' loop (residues 374–398). This loop protrudes into the central channel of the portal assembly and has lower density than the rest of the structure, suggesting flexibility. In the portal structures of the SPP1, P22 and φ29 this loop is 14, 10 and 23 amino-acid long, respectively, and is mostly completely disordered. The stem region consists of two helices, α5 and α7, that are oriented at an angle of about 40° with respect to the central 12-fold axis and are connected to each other by the clip domain. The clip domain (residues 279–358) consists of three β-strands and helix α6. This domain is exposed on the outside of the capsid. It is the site of attachment of the packaging ATPase, gp17, during DNA packaging, as well as for attachment of the neck (gp13) and tail in the mature phage.

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.