Icosahedral virus particles

An icosahedral virus particle composed of 252 capsomeres 240 being hexons and 12 being pentons... 

Icosahedral virus particles as addressable nanoscale building blocks, Q. Wang, T. Lin,... 

Q. Wang, T.W. Lin, L. Tang, J.E. Johnson, M.G. Finn, Icosahedral virus particles as addressable nanoscale building blocks, Angew. Chem. Int. Ed. Engl. 2002, 41, 459-462. 

The CPMV is also an RNA-containing plane virus. The icosahedral virus particle is formed from 60 copies of two different types of protein subunits (large 37 kDa and small 23 kDa). These proteins assemble into a pseudo (7 = I) particle approximately 30 nm in diameter. Very high... 

Fig. 1 Assembly of T = 3 icosahedral virus particle showing the three subunits of the asymmetric unit Al, BI, Cl. (Used with permission from http //mmtsb.scripps.edu/viper/viper.htm)...

A recent series of articles illustrated the potential of using viruses as addressable nanoblocks having a variety of chemical and physical properties. These icosahedral virus particles can be derivatized using fluorescent organic labels or particles of nanogold.This is an illustration of the use of chemical functionality in a... 

Escherichia coli was characterized by IM(TOF)MS with a MALDI source and with an ESI source." " . The preseparation afforded by the mobility spectrometer made it possible to separate metabolites in the mass range below 1,800 Da. ESI-IMS was also used to characterize intact virus particles, and it was found that icosahedral virus particles retain their structure in the gas phase. ... 

Figure 1. Cysteine-mutant of CPMV. PDB file available for wild type virus (INYV.pdb). (a) A 30 nm diameter icosahedral virus particle, EF-CPMV, made of 60 identical protein subunits containing a total of 60 cysteines (thiol-containing group shown as white circles), (b) EF-CPMV protein subunit to which a single cysteine was incorporated via the addition of a five residue loop (GGCGG) placed between positions 98 and 99(20). (Adapted with permission from reference (21). Copyright 2006, American Chemical Society.)...

Virus-glycopolymer conjugates are constructed from azide-modifled viral protein scaffolds with alkynes to provide the end-functionalized products Icosahedral virus particles... 

Strable, E., Johnson, J. E., and Finn, M. G. [2004J. Natural nanochemical building blocks Icosahedral virus particles organized by attached oligonucleotides. Nano Lett, 4,1385-1389. 

Figure 5.6 A simple icosahedral virus. Each face has three subunits. A single subunit consists of one or more proteins, (a) Whole virus particle, (b) Virus particle opened up nucleic acid released.

Complex viruses Some virions are even more complex, being composed of several separate parts, with separate shapes and symmetries. The most complicated viruses in terms of structure are some of the bacterial viruses, which possess not only icosahedral heads but helical tails. In some bacterial viruses, such as the T4 virus of Escherichia coli, the tail itself is a complex structure. For instance, T4 has almost 20 separate proteins in the tail, and the T4 head has several more proteins. In such complex viruses, assembly is also complex. For instance, in T4 the complete tail is formed as a subassembly, and then the tail is added to the DNA-containing head. Finally, tail fibers formed from another protein are added to make the mature, infectious virus particle. 

The bacterial RNA viruses are all of quite small size, about 26 nm in size, and they are all icosahedral, with 180 copies of coat protein per virus particle. The complete nucleotide sequence of several RNA phages are known. In the RNA phage MS2, which infects Escherichia coli, the viral RNA is 3,569 nucleotides long. The virus RNA, although single stranded, has extensive regions of secondary and tertiary structure. The RNA strand in the virion has the plus (+) sense, acting directly as mRNA upon entry into the cell. 

Bacteriophage T7 Bacteriophage T7 and its close relative T3 are relatively small DNA viruses that infect Escherichia coli. (Some strains of Shigella and Pasteurella are also hosts for phage T7.) The virus particle has an icosahedral head and a very small tail. The virus particle is fairly complex, with S different proteins in the head and 3-6 different proteins in the tail. One tail protein, the tail fiber protein, is the means by which the virus particle attaches to the bacterial cell surface. Only female cells of Escherichia coli can be infected with T7 male cells can be infected but the multiplication process is terminated during the latent period. 

The virus particle of phage T4 is structurally complex. It consists of an icosahedral head which is elongated by the addition of one or two extra bands of protein hexamers, the overall dimensions of the... 

The presence of human papilloma virus (HPV) is associated with female genital tract diseases such as condyloma, Bowenoid papulosis, and cervical, vaginal, and vulvar intraepithelial neoplasia and carcinoma. A general concern is the association of HPV with cervical cancer (Gl). The HPV consists of an icosahedral viral particle (virion) containing 8000 base pairs, a circular, double-stranded piece of DNA surrounded by a protein capsid. Viral replication takes place within the nuclei of infected squamous epithelial cells (H5). Following infection of epithelial cells, the viral DNA penetrates throughout the entire thickness of the epithelium, but intact viruses are found only in the upper layers of tissue. 

One of the most intriguing recent examples of disordered structure is in tomato bushy stunt virus (Harrison et ah, 1978), where at least 33 N-terminal residues from subunit types A and B, and probably an additional 50 or 60 N-terminal residues from all three subunit types (as judged from the molecular weight), project into the central cavity of the virus particle and are completely invisible in the electron density map, as is the RNA inside. Neutron scattering (Chauvin et ah, 1978) shows an inner shell of protein separated from the main coat by a 30-A shell containing mainly RNA. The most likely presumption is that the N-terminal arms interact with the RNA, probably in a quite definite local conformation, but that they are flexibly hinged and can take up many different orientations relative to the 180 subunits forming the outer shell of the virus particle. The disorder of the arms is a necessary condition for their specific interaction with the RNA, which cannot pack with the icosahedral symmetry of the protein coat subunits. 

Electron microscopic studies have suggested that the alphavirus particle has icosahedral symmetry (see below). The triangulation number is not certain, however (Murphy, 1980). Previous estimates for the molecular weight were compatible with 240 subunits per virus particle, and electron micrographs appear to show a T = 4 surface lattice (von Bons-dorff and Harrison, 1975). More information is now needed to determine the surface organization, since compositional data show fewer than 240 subunits. 

Ochoa WF et al (2006) Generation and structural analysis of reactive empty particles derived from an icosahedral virus. Chem Biol 13 771-778 PDBID 2BFU... 

---