Rhinovirus icosahedral

Fig. 9.13 An icosahedral host, (a) X-ray crystal struture of the rhino-virus, a spherical virus linked to the common cold, (b) a schematic representation of the rhinovirus displaying triangulation.

Schematic illustration of the icosahedral rhinovirus 14. (a) Shown is the icosahedron comprised of 60 copies each of VP1 (light gray), VP2 (black), and VP3 (gray). The shaded circles around each five-fold axis indicate the canyon positions. Also indicated is the approximate position of the VP1 hydrophobic pocket that lies underneath the surface of the virion, (b) An icosahedral pentamer is expanded with one viral protomer shown as a protein ribbon diagram, (c) This pentamer is seen in a cutaway view. Here VP1 is white, VP2 and VP4 black, and VP3 gray. A capsid-binding compound is depicted as black spheres inside the VP1 ribbon diagram. The cross hatched regions on the (c) schematic (right) indicate areas that disorder when HRV14 crystals are exposed to acid.

Figure 7-15 (A) Schematic diagram of the icosahedral shell of a human rhinovirus showing the arrangement of the three subunits VP1, VP2, and VP3, each present as 60 copies. (B) Stereoscopic view of an image of the virus "decorated" by the binding of two immunoglobulinlike domains of the intercellular adhesion molecule ICAM-1, a natural receptor for the virus.

Related picoma viruses such as human rhinoviruses (Fig. 7-15),69/78/79 foot-and-mouth disease virus, parvovirus,80 and Mengo virus81 have similar architectures. The small (diameter 25 nm) single-stranded DNA bacteriophages such as ( )X174 also have three different coat proteins, one of which forms small hollow spikes at the vertices of the icosahedral shell (Fig. 5-41A).82... 

With respect to immobile chiroids, the appropriate symmetries are given by the familiar finite point groups C, (nonaxial), C (monoaxial), Dn (dihedral), T (tetrahedral), 0 (octahedral), and I (icosahedral). Molecules that belong to the first three groups are commonplace molecules with ground-state symmetries T [example tetrakis(trimethylsilyl)silane],39 O (example appoferritin 24-mer),40 and 1 (example human rhinovirus 60-mer),40 are relatively uncommon. 

The complete, mature virus particle is known as a virion and usually has a regular shape. Many virions are icosahedral, that is, the capsid is formed from identical protein subunits (capsomeres) that combine to produce a solid with twenty faces, each of which is an equilateral triangle. The herpes viruses are of this type, as are the picomaviruses of which the polio viruses and rhinoviruses (cold viruses) are the bestknown members. The other common regular shape is that of a helix, and the tobacco mosaic virus is of this type. Its single helical strand of RNA is enclosed within a hollow tube, which comprises 2130 protein subunits arranged in a helix. Other viruses with a similar structure are the... 

About two-thirds of colds are caused by rhinoviruses - members of the picomavirus group (as are the polio viruses), and all of them are RNA-(+)-viruses. These have an icosahedral (20-sided, near-spherical) shape and their protein coat is made from four different proteins with widely differing amino acid compositions. It is not therefore surprising that there are more than 90 serotypes hence, there is little possibility of a useful vaccine, and none of us has much chance of becoming immune to all forms of the common cold. Other viruses that produce the symptoms of a cold include coronaviruses, adenoviruses, coxsackie viruses, orthomyxoviruses, paramyxoviruses, respiratory syncitial viruses, echoviruses and enteroviruses. 

Rhinoviruses belong to the picornaviridae family small icosahedral viruses with an average diameter of 300 A and a molecular mass of approximately 8.5 X 10 Da. Like all picornaviruses, HRVs are made of a protein capsid that encases a single-stranded, positive-sense RNA molecule of about 7000 bases. The capsid is built from 60 copies of viral proteins 1, 2, 3 and 4 (VPl, VP2, VP3, and VP4). VPl, VP2 and VP3 assemble on the exterior to form the protein shell, and VP4 resides in the interior of the capsid,... 

Accordingly, all vertices of the molecular form encapsulating the capsid of the rhinovirus are at points of the same icosahedral lattice, proving that the icosahedral lattice is indeed the form lattice for the viral capsid, which has its envelope and hole related by a three-dimensional crystallographic scaling. This property provides an answer to the first question. 

Figure 11-8. The capsid of the human rhinovirus is enc sulated between two ico-dodecahedra, one external and one internal scaled with a factor 1/r, with r the golden ratio. All vertices belong to the same icosahedral lattice. Only the vertices and the monomeric chains of the four coat proteins VPl, VP2, VP3 and VP4 in die various equatorial regions are plotted in projected views along the fivefold, the twofold and die direefold axes, respectively (adapted from [27], courtesy lUCr)...

Figure 11-9. The cluster with 222 symmetry of four VPl coat proteins taken from the human rhinovirus is enclosed in molecular forms with vertices at points of an integral tetragonal lattice with lattice parameters a = ra( /9, b = c = tuq/S, in which Uq is the icosahedral lattice parameter and t the golden ratio (adapted from [27], courtesy lUCr)...

Supramolecular chirality is widely manifested in nature for example, the DNA double helix,the protein single helices and, in humans, rhinovirus 14, a member of the major rhinoviras receptor class, possesses a protein capsid that is composed of 60 protomers arranged in an icosahedrally symmetric arrayJ As shown previously in this book, at the molecular level, chirality is very important in asymmetric catalysis for the creation of novel chiral molecules however, more recently an increasing amount of attention has been drawn to chiral supramolecular assemblies. On the supramolecular level, chirality involves the nonsymmetric arrangement of molecular subunits in a noncovalent assembly via weak interactions such as hydrogen bonding, metal coordination and n-n interaction. 

Cryoelectron microscopy image of rhinovirus 14, showing Icosahedral protein shell, [Dr, Timothy Baker, N. Olson, T. J. Smith/Visuals Unlimited.)... 

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