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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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One of the six helical strands of gp18 that form the T4 tail sheath in the extended (green) and contracted (brown) states. The hexagonally shaped baseplate, tail tube and collar of the extended tail are also shown (blue). The extended sheath makes about one turn around the tail tube, whereas the contracted sheath makes about two turns, thus causing the tail tube and head to rotate while entering the periplasmic space of the E. coli host. (Adapted from Kostyuchenko et al., 2005 ▶.)
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fig10: One of the six helical strands of gp18 that form the T4 tail sheath in the extended (green) and contracted (brown) states. The hexagonally shaped baseplate, tail tube and collar of the extended tail are also shown (blue). The extended sheath makes about one turn around the tail tube, whereas the contracted sheath makes about two turns, thus causing the tail tube and head to rotate while entering the periplasmic space of the E. coli host. (Adapted from Kostyuchenko et al., 2005 ▶.)

Mentions: Although the structure of the sheath protein, gp18, is still unknown, it was possible to determine the shape of the protein and to observe that this protein can be segmented into three domains whose relative positions change when the sheath contracts. The gp18 protein subunits form a six-start right-handed helix around the tail tube generated by 23 hexameric rings. In the extended tail, these rings are rotated by 17.2° relative to each neighboring ring, forming a sheath around the tail tube that is 925 Å in length and has a 240 Å diameter. However, the contracted sheath is only 420 Å in length, but is 330 Å in diameter, with a rotation of 32.9° between successive rings. Thus, each of the six helices that form the sheath makes a 378.4° rotation around the tube when extended or a 782° rotation when contracted (Fig. 10 ▶). That means while the baseplate is firmly attached to the E. coli surface, the tail tube, terminating with the gp5 β-helical ‘pin’, rotates 345.4° (roughly one revolution) like a drill while being pushed through the baseplate across the E. coli periplasmic space by almost 505 Å. This process also causes the three lysozyme subunits to be pushed onto the peptidoglycan cell wall for digestion.


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)

One of the six helical strands of gp18 that form the T4 tail sheath in the extended (green) and contracted (brown) states. The hexagonally shaped baseplate, tail tube and collar of the extended tail are also shown (blue). The extended sheath makes about one turn around the tail tube, whereas the contracted sheath makes about two turns, thus causing the tail tube and head to rotate while entering the periplasmic space of the E. coli host. (Adapted from Kostyuchenko et al., 2005 ▶.)
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig10: One of the six helical strands of gp18 that form the T4 tail sheath in the extended (green) and contracted (brown) states. The hexagonally shaped baseplate, tail tube and collar of the extended tail are also shown (blue). The extended sheath makes about one turn around the tail tube, whereas the contracted sheath makes about two turns, thus causing the tail tube and head to rotate while entering the periplasmic space of the E. coli host. (Adapted from Kostyuchenko et al., 2005 ▶.)
Mentions: Although the structure of the sheath protein, gp18, is still unknown, it was possible to determine the shape of the protein and to observe that this protein can be segmented into three domains whose relative positions change when the sheath contracts. The gp18 protein subunits form a six-start right-handed helix around the tail tube generated by 23 hexameric rings. In the extended tail, these rings are rotated by 17.2° relative to each neighboring ring, forming a sheath around the tail tube that is 925 Å in length and has a 240 Å diameter. However, the contracted sheath is only 420 Å in length, but is 330 Å in diameter, with a rotation of 32.9° between successive rings. Thus, each of the six helices that form the sheath makes a 378.4° rotation around the tube when extended or a 782° rotation when contracted (Fig. 10 ▶). That means while the baseplate is firmly attached to the E. coli surface, the tail tube, terminating with the gp5 β-helical ‘pin’, rotates 345.4° (roughly one revolution) like a drill while being pushed through the baseplate across the E. coli periplasmic space by almost 505 Å. This process also causes the three lysozyme subunits to be pushed onto the peptidoglycan cell wall for digestion.

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