Viral capsids, self-assembly

The non-enveloped human viruses all have icosahedral capsids. The structural proteins undergo a self-assembly process to form capsids into which the viral nucleic acid is packaged. Most non-enveloped viruses accumulate within the cytoplasm or nucleus and are only released when the cell lyses. 

Vainshtein, B. K. (1966). Diffraction of X-Rays by Chain Molecules. Elsevier, Amsterdam. Valery, C., Patemostre, M., Robert, B., Gulik-Krzywicki, T., Narayanan, T., Dedieu, J. C., Keller, G., Torres, M. L., Cherif-Cheikh, R., Calvo, P., and Artzner, F. (2003). Biomimetic organization Octapeptide self-assembly into nanotubes of viral capsid-like dimension. Proc. Natl. Acad. Sci. USA 100, 10258-10262. 

In a paper describing the structure of regular viruses, Caspar and Klug [4] have shown that viral capsids use self-assembly to construct spherical shells up to a hundred nanometers in diameter by utilizing identical copies of proteins as chemical... 

Biochemical self-assembly proceeds by fundamental supramolecular principles and can lead to structures of startling complexity including DNA and viral capsids. 

We have already dealt with some general aspects of biochemical self-assembly in Section 2.10 including the remarkable formation of viral capsids. There are some biochemical examples, however, that translate readily into supramolecular chemical concepts and have been pivotal in defining the field. One such system is the tobacco mosaic virus, a virus that is very harmful to a variety of crops including tobacco, tomato, pepper, cucumbers and species such as ornamental flowers. This system consists of a helical virus particle measuring some 300 X 18 nm (Figure 10.6). A central strand of RNA is sheathed by 2130 identical protein subunits, each of which contains 158 amino acids. What is remarkable about... 

Virus-like particles (VLPs) (Noad and Roy 2003) are produced from viral capsid proteins. The capsid proteins self-assemble to form particles that resemble the virus from which the capsid proteins were derived, but lack any... 

As large amounts of viral materials accumulate within the cell, the role of structural proteins becomes evident. The structural proteins of small non-enveloped viruses (e.g. poliovirus) self-assemble once they are synthesized. Initially individual units form capsomeres, which then associate into capsids. The viral genome and associated... 

Consultation of polyhedron models revealed the structure of 1 to conform to a snub cube, one of the 13 Archimedean solids, in which the vertices of the square faces correspond to the comers of 2 and the centroids of the eight triangles that adjoin three squares correspond to the eight water molecules. Indeed, to us, the ability of six resorcin[4]arenes to self-assemble to form 1 was reminiscent of spherical viruses in which identical copies of proteins self-assemble, by way of noncovalent forces, to form viral capsids having icosahedral symmetry and a shell-like enclosure. In fact, owing to the fit displayed by its components, 1 exhibits a topology that agrees with the theory of vims shell stmcture which states that... 

Viruses are similar to biomolecular templates because the viral capsid is in fact a complex composed of protein subunits. Viruses coupled with nanoparticles can be used as building blocks to form nanoparticle assemblies or virus assemblies of two and three dimensions can be used as templates. Virus is advantageous as a building block because identical viruses can be produced in large amounts at low cost, and nanoparticles templated by viruses generally have a high monodispersity. Viruses may have inherent self-assembly, for example, nanowires mineralized... 

Unlike bacteria, virus particles (virons) are capable of replication only within a host cell. Once within the host cell, the viral nucleic acid directs the synthesis of specific enzymes needed to replicate itself, and directs the synthesis of the viral-coating protein (capsid). The capsid protects the nucleic acid from enzyme attack, and in the absence of high temperatures (above about 70°C the virus may remain intact for several decades. Separation of the nucleic acid from the capsid is necessary in order that the virus becomes active, but the separated components appear to have the capacity for self-assembly to reconstruct the virus particle. 

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