Capsid protein

A second model to account for the observed inhibition of cellular mRNA translation developed from a genetic analysis of temperature-sensitive mutants of poliovirus. These mutants were screened for their ability to repress protein synthesis after infection in the presence of guanidine at restrictive temperature (Steiner-Pryor and Cooper, 

which proposed that a complex of capsid proteins combined with the ribosomal subunit and thereby prevented its association with cellular (but presumably not viral) mRNA. Several questions can be raised about the genetic experiments and the assay used to determine the ability of various mutants to inhibit protein synthesis under various conditions. At higher multiplicities of infection, all of the mutants did repress protein synthesis at both temperatures, although to variable extents. Measurements at a single time point may have revealed differences in the rate of inhibition as opposed to the absolute ability to inhibit. Mutations in the capsid protein gene(s) may have altered 

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The capsids of polyoma virus and the related SV40 have icosahedral symmetry, with 72 pentameric assemblies of the major capsid protein. The pentamers are linked to their neighbors by flexible arms, with a p strand that augments a p sheet in the invaded pentamer. These flexible arms allow the pentamers to be linked together with both fivefold and sixfold symmetry. 

Rossmann, M.G. Antiviral agents targeted to interact with viral capsid proteins and a possible application to human immunodeficiency virus. Proc. Natl. Acad. Sci. USA, 85 4625-4627, 1988. 

Tang C, LoeUger E, Kinde I et al. (2003) Antiviral inhibition of the HIV-1 capsid protein. J Mol Biol 327 1013-1020... 

All enveloped human vimses acquire their phospholipid coating by budding through cellular membranes. The maturation and release of enveloped influenza particles is illustrated in Fig. 3.8. The capsid protein subunits are transported flom the ribosomes to the nucleus, where they combine with new viral RNA molecules and are assembled into the helical capsids. The haemagglutinin and neuraminidase proteins that project fiom the envelope of the normal particles migrate to the cytoplasmic membrane where they displace the normal cell membrane proteins. The assembled nucleocapsids finally pass out from the nucleus, and as they impinge on the altered cytoplasmic membrane they cause it to bulge and bud off completed enveloped particles flxm the cell. Vims particles are released in this way over a period of hours before the cell eventually dies. 

The human caliciviruses, norovirus (NoV) and sapovirus, have also been described as small round structured viruses, for their 27-30 nm capsids. The NoV capsid consists of 180 copies of the VPl major capsid protein packed as an icosahedron (Prasad et ah, 1999) and the VP2 minor capsid protein, which may contribute to stability (Bertolotti-Ciarlet et al., 2002). The S domain of VPl forms the inner shell of the capsid, while the P domain protrudes from the capsid surface and contributes to binding the histoblood group antigen receptor (Cao et ah, 2007) and antigenicity (Donaldson et ah, 2008 Lindesmith et ah, 2010). 

Sequence analysis of the major capsid protein, VPl, groups NoV into five genogroups that contain at least 29 genetic clusters (Zheng et al.,... 

The diagnosis of hepatitis A is made by detecting immunoglobulin antibody to the capsid proteins of the HAV. The presence of IgM anti-HAVin the serum indicates an acute infection. IgM appears approximately 3 weeks after exposure and becomes undetectable within 6 months. In contrast, IgG anti-HAV appears in the serum at approximately the same time IgM anti-HAV develops but indicates protection and lifelong immunity against hepatitis A.1... 

Figure 2 The three-dimensional structure of HRV-114 consisting of four viral proteins, VP1, VP2, and VP3 Vp4 is pointing toward the center of the capsid protein and is not visible.

Santini, C., Brennan, D., Mennuni, C., Hoess, R. H., Nicosia, A., Cortese, R., and Luzzago, A. (1998). Efficient display of an HCV cDNA expression library as C-terminal fusion to the capsid protein D ofbacteriophage lambda. J. Mol. Biol. 282, 125-135. 

Yoshida T, Sano T, Kanuma T, et al. Immunochemical analysis of HPV LI capsid protein and pl6 protein in liquid-based cytology samples from uterine cervical lesions. Cancer (Cancer Cytopathol.) 2008 114 83-88. 

Human papilloma virus type 11 major capsid protein LI Tobacco leaf, potato tuber Reacted well with assembled capsids and isolated LI capsomers. Immunogenic in mice when administered parenterally with subsequent oral boosting. 99... 

Human papilloma virus (HPV) type 16 major capsid protein LI Tobacco leaf Neutralizing monoclonal antibodies bound plant-produced particles. 101... 

Norwalk virus (NV) capsid protein Potato tuber tobacco leaf Mice and humans developed serum IgG and secretory IgA specific for recombinant NV. Immunogenic in mice and humans when administered orally. 45,57... 

An additional virus that has more recently gained some attention as a possible vector is that of the sindbis virus. A member of the alphavirus family, this ssRNA virus can infect a broad range of both insect and vertebrate cells. The mature virion particles consist of the RNA genome com-plexed with a capsid protein C. This, in turn, is enveloped by a lipid bilayer in which two additional viral proteins (El and E2) are embedded. The E2 polypeptide appears to mediate viral binding to the surface receptors of susceptible cells. The major mammalian cell surface receptor it targets appears to be the highly conserved, widely distributed laminin receptor. 

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