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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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Structure of the pentameric vertex of the T4 gp24 bypass mutant viewed down the fivefold axis of the capsid. The soc molecules are colored grey. The additional soc molecules bound around the gp23* pentamers are marked in red. Reprinted from Fokine et al. (2006 ▶) with permission from Elsevier.
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fig6: Structure of the pentameric vertex of the T4 gp24 bypass mutant viewed down the fivefold axis of the capsid. The soc molecules are colored grey. The additional soc molecules bound around the gp23* pentamers are marked in red. Reprinted from Fokine et al. (2006 ▶) with permission from Elsevier.

Mentions: The T4 phage head consists of hexagonally packed planes of gp23 hexamers. The fivefold icosahedral vertices occur at the intersection of these planes, requiring a special pentagonal vertex protein. Apparently, the primordial phage had only one type of protein, but with gene duplication the specialized protein evolved independently of the major capsid protein gp23. A reversion to the primordial phage is produced by ‘bypass’ mutations in which the absence of the gp24 gene is compensated by mutations in gp23 (Fokine et al., 2006 ▶; Fig. 6 ▶)


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)

Structure of the pentameric vertex of the T4 gp24 bypass mutant viewed down the fivefold axis of the capsid. The soc molecules are colored grey. The additional soc molecules bound around the gp23* pentamers are marked in red. Reprinted from Fokine et al. (2006 ▶) with permission from Elsevier.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig6: Structure of the pentameric vertex of the T4 gp24 bypass mutant viewed down the fivefold axis of the capsid. The soc molecules are colored grey. The additional soc molecules bound around the gp23* pentamers are marked in red. Reprinted from Fokine et al. (2006 ▶) with permission from Elsevier.
Mentions: The T4 phage head consists of hexagonally packed planes of gp23 hexamers. The fivefold icosahedral vertices occur at the intersection of these planes, requiring a special pentagonal vertex protein. Apparently, the primordial phage had only one type of protein, but with gene duplication the specialized protein evolved independently of the major capsid protein gp23. A reversion to the primordial phage is produced by ‘bypass’ mutations in which the absence of the gp24 gene is compensated by mutations in gp23 (Fokine et al., 2006 ▶; Fig. 6 ▶)

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