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From structure of the complex to understanding of the biology.

Rossmann MG, Arisaka F, Battisti AJ, Bowman VD, Chipman PR, Fokine A, Hafenstein S, Kanamaru S, Kostyuchenko VA, Mesyanzhinov VV, Shneider MM, Morais MC, Leiman PG, Palermo LM, Parrish CR, Xiao C - Acta Crystallogr. D Biol. Crystallogr. (2006)

Bottom Line: Both techniques lean heavily on imposing icosahedral symmetry, thereby obscuring any deviation from the assumed symmetry.However, tailed bacteriophages have icosahedral or prolate icosahedral heads that have one obvious unique vertex where the genome can enter for DNA packaging and exit when infecting a host cell.Comparisons are made between rhinoviruses that bind receptor molecules uniformly to all 60 equivalent binding sites, canine parvovirus, which appears to have a preferred receptor-binding site, and bacteriophage T4, which gains major biological advantages on account of its unique vertex and tail organelle.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, IN 47907-2054, USA. mr@purdue.edu

ABSTRACT
The most extensive structural information on viruses relates to apparently icosahedral virions and is based on X-ray crystallography and on cryo-electron microscopy (cryo-EM) single-particle reconstructions. Both techniques lean heavily on imposing icosahedral symmetry, thereby obscuring any deviation from the assumed symmetry. However, tailed bacteriophages have icosahedral or prolate icosahedral heads that have one obvious unique vertex where the genome can enter for DNA packaging and exit when infecting a host cell. The presence of the tail allows cryo-EM reconstructions in which the special vertex is used to orient the head in a unique manner. Some very large dsDNA icosahedral viruses also develop special vertices thought to be required for infecting host cells. Similarly, preliminary cryo-EM data for the small ssDNA canine parvovirus complexed with receptor suggests that these viruses, previously considered to be accurately icosahedral, might have some asymmetric properties that generate one preferred receptor-binding site on the viral surface. Comparisons are made between rhinoviruses that bind receptor molecules uniformly to all 60 equivalent binding sites, canine parvovirus, which appears to have a preferred receptor-binding site, and bacteriophage T4, which gains major biological advantages on account of its unique vertex and tail organelle.

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Related in: MedlinePlus

Cryo-EM reconstruction of the head capsid of bacteriophage T4, based on fivefold symmetry averaging. The major capsid protein (gp23, in blue) forms hexamers. The small outer capsid protein (soc, in white) binds between gp23 hexamers. The highly antigenic outer capsid protein (hoc, in yellow) binds at the center of gp23 hexamers. Pentamers of the special vertex protein gp24 (purple) are at the icosahedral vertices. The tail (green) is smeared as it has sixfold symmetry, not the fivefold symmetry used for averaging.
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fig5: Cryo-EM reconstruction of the head capsid of bacteriophage T4, based on fivefold symmetry averaging. The major capsid protein (gp23, in blue) forms hexamers. The small outer capsid protein (soc, in white) binds between gp23 hexamers. The highly antigenic outer capsid protein (hoc, in yellow) binds at the center of gp23 hexamers. Pentamers of the special vertex protein gp24 (purple) are at the icosahedral vertices. The tail (green) is smeared as it has sixfold symmetry, not the fivefold symmetry used for averaging.

Mentions: The icosahedral ends of bacteriophage T4 heads have T = 13 quasi-symmetry and the cylindrical mid-section has Q = 20 quasi-symmetry (Fokine et al., 2004 ▶). The protein shell of the mature T4 capsid is formed by the major capsid protein gp23, the special vertex protein gp24, the highly antigenic outer capsid protein (hoc), the small outer capsid protein (soc) and the head–tail connector gp20. Cryo-EM reconstructions have identified the location of these proteins in the head (Fig. 5 ▶) (Fokine et al., 2004 ▶). The major capsid protein forms a hexagonal array of hexamers. The soc proteins bind to the interface between gp23 hexamers.


From structure of the complex to understanding of the biology.

Rossmann MG, Arisaka F, Battisti AJ, Bowman VD, Chipman PR, Fokine A, Hafenstein S, Kanamaru S, Kostyuchenko VA, Mesyanzhinov VV, Shneider MM, Morais MC, Leiman PG, Palermo LM, Parrish CR, Xiao C - Acta Crystallogr. D Biol. Crystallogr. (2006)

Cryo-EM reconstruction of the head capsid of bacteriophage T4, based on fivefold symmetry averaging. The major capsid protein (gp23, in blue) forms hexamers. The small outer capsid protein (soc, in white) binds between gp23 hexamers. The highly antigenic outer capsid protein (hoc, in yellow) binds at the center of gp23 hexamers. Pentamers of the special vertex protein gp24 (purple) are at the icosahedral vertices. The tail (green) is smeared as it has sixfold symmetry, not the fivefold symmetry used for averaging.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2483488&req=5

fig5: Cryo-EM reconstruction of the head capsid of bacteriophage T4, based on fivefold symmetry averaging. The major capsid protein (gp23, in blue) forms hexamers. The small outer capsid protein (soc, in white) binds between gp23 hexamers. The highly antigenic outer capsid protein (hoc, in yellow) binds at the center of gp23 hexamers. Pentamers of the special vertex protein gp24 (purple) are at the icosahedral vertices. The tail (green) is smeared as it has sixfold symmetry, not the fivefold symmetry used for averaging.
Mentions: The icosahedral ends of bacteriophage T4 heads have T = 13 quasi-symmetry and the cylindrical mid-section has Q = 20 quasi-symmetry (Fokine et al., 2004 ▶). The protein shell of the mature T4 capsid is formed by the major capsid protein gp23, the special vertex protein gp24, the highly antigenic outer capsid protein (hoc), the small outer capsid protein (soc) and the head–tail connector gp20. Cryo-EM reconstructions have identified the location of these proteins in the head (Fig. 5 ▶) (Fokine et al., 2004 ▶). The major capsid protein forms a hexagonal array of hexamers. The soc proteins bind to the interface between gp23 hexamers.

Bottom Line: Both techniques lean heavily on imposing icosahedral symmetry, thereby obscuring any deviation from the assumed symmetry.However, tailed bacteriophages have icosahedral or prolate icosahedral heads that have one obvious unique vertex where the genome can enter for DNA packaging and exit when infecting a host cell.Comparisons are made between rhinoviruses that bind receptor molecules uniformly to all 60 equivalent binding sites, canine parvovirus, which appears to have a preferred receptor-binding site, and bacteriophage T4, which gains major biological advantages on account of its unique vertex and tail organelle.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, IN 47907-2054, USA. mr@purdue.edu

ABSTRACT
The most extensive structural information on viruses relates to apparently icosahedral virions and is based on X-ray crystallography and on cryo-electron microscopy (cryo-EM) single-particle reconstructions. Both techniques lean heavily on imposing icosahedral symmetry, thereby obscuring any deviation from the assumed symmetry. However, tailed bacteriophages have icosahedral or prolate icosahedral heads that have one obvious unique vertex where the genome can enter for DNA packaging and exit when infecting a host cell. The presence of the tail allows cryo-EM reconstructions in which the special vertex is used to orient the head in a unique manner. Some very large dsDNA icosahedral viruses also develop special vertices thought to be required for infecting host cells. Similarly, preliminary cryo-EM data for the small ssDNA canine parvovirus complexed with receptor suggests that these viruses, previously considered to be accurately icosahedral, might have some asymmetric properties that generate one preferred receptor-binding site on the viral surface. Comparisons are made between rhinoviruses that bind receptor molecules uniformly to all 60 equivalent binding sites, canine parvovirus, which appears to have a preferred receptor-binding site, and bacteriophage T4, which gains major biological advantages on account of its unique vertex and tail organelle.

Show MeSH
Related in: MedlinePlus