Capsid architecture

Merckel, M. C., Huiskonen, J. T., Bamford, D. H., Goldman, A., and Tuma, R. (2005). The structure of the bacteriophage PRD1 spike sheds light on the evolution of viral capsid architecture. Mol. Cell 18, 161-170. 

Fisher, A. J., and Johnson, J. E. (1993). Ordered duplex RNA controls capsid architecture in an icosahedral animal virus. Nature 361, 176-179. 

The problem of picomavirus capsid architecture was resolved by Rueckert and his collaborators (55>54) who, instead of examining the intact virion, studied the dissociation products which result when pxirified cardioviruses are incubated at pH 5 - 6.5 the presence of 0.1 chloride ions. By analytical ultracentrifugation and SBS-polacrylamide gel electrophoretic analyses they found that the primary product of such a dissociation is a protein moiety which has a sedimentation coefficient of 13-14 > a molecular weight of about 425> 000 and which contains equimolar proportions of the viral polypeptides a, 3 and Y. The small viral polypeptide species, 6, and the intact RNA are precipitated during the dissociation. 

The general features of picornavirus capsid architecture which have been revealed by chemical labeling and immunological experiments are as follows. 

Brome mosaic viruses (BMV) readily infect different varieties of grasses and to a minor extent maize. Collectively, BMV is among the smallest virases with an icosahedral protein capsid of 27 run in diameter, and in contrast to most other viruses, is cationic at pH below 6.5. The architecture of the capsid portion of the virus is constracted from 180 protein capsomeres that are independently stabilized by weak electrostatic interactions with the negatively charged RNA core (3234, 2865, 2114, and 876 nucleotides). Kao etal. have developed an approach to replacing this RNA core with... 

No crystallographic structure is currently available for GPV-type single-shelled dsRNA virus capsids. Two cryo-EM reconstructions have been performed, which reveal much the same architecture as the orthoreovirus core a single layer with turrets at the 5-fold vertices, statistically ordered layers of dsRNA, and a clamping protein at 2-fold axes (Hill et al, 1999 ... 

These studies have all shown the importance of hybrid technology. Antibodies have been used to elucidate the architecture of viruses and to identify receptor-binding regions. They have directly addressed the mechanism of antibody-mediated neutralization, which has greatly impacted the development of vaccines. Finally, they have improved our understanding about the forces that have driven the evolution of viral structure. It is likely that such studies will continue to help us understand the architecture of macro-macromolecular complexes and the dynamics of these viral capsids. 

FIGURE 14.1 The architecture of a typical virus particle. The nucleic acid is in the middle, surrounded by a protein coat called the capsid. Many viruses also have an envelope membrane that is usually covered with protein spikes. 

Several approaches have recently been developed that directly apply natural architectures for artificial chanical reactions, some of which are detailed in different chapters of this book. Although not classified as homogeneous catalysis, the reduction of metal salts inside nanoreactors could be the first step on the way to reactivity with the corresponding metal coUoids or nanoparticles in e.g. hydrogenation reactions. A variety of carrier systems have been studied lately, including virus capsids, polymeric micelles, miniemulsions and hollow core-shell particles, as nanoreactors and hosts for the synthesis and encapsnlation of well-defined, stable nanoparticles. ... 

Figure 6 Some examples of biological building block used in hybrid materials, (a) Cyclic peptides as membrane (xjres (b) a schanatic of a virus showing DNA within the capsid (c) a DNA Holliday junction, which aeates a comer motif within a cubic DNA architecture and (d) the seqnence of DNA can be manipnlated for molecnlar computation and simple logic games snch as tic-tac-toe. ...

Synthetic control over the physical and chemical properties of a nanoparticle can be tuned according to its biological micro- or nano-environment. Some of the most notable platforms that are currently being used for the controlled synthesis of metal oxides include the apoprotein ferritin, viral capsids or bacterial cages however, recently adapted biotemplates, such as self-assemble peptide nanorings or porous butterfly wings, have been used as unique platforms and have yielded interesting structures. These molecular architectures offer constrained environments that yield a small distribution of nanoparticle size under ambient conditions, and will be discussed as viable alternatives for the synthesis of functional nanomaterials. 

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