Physical Principles in the Construction of Regular Viruses

Caspar, D. L. D.; Klug, A

doi:10.1101/sqb.1962.027.001.005

Cited by 2,246 publications

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“…38) icosahedral symmetry, and shows protrusions on the 3-fold axes, in the centre of the triangle formed by adjacent 5-and 3-fold axes, and midway between the 5-and 3-fold axes. The F polypeptide was easily traced with confidence except for the first and last two residues which are disordered.…”

Section: Protein Structurementioning

confidence: 99%

Atomic structure of single-stranded DNA bacteriophage ΦX174 and its functional implications

McKenna

Xia

Willingmann

et al. 1992

Nature

217

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The mechanism of DNA ejection, viral assembly and evolution are related to the structure of bacteriophage ΦX174. The F protein forms a T = 1 capsid whose major folding motif is the eightstranded antiparallel β barrel found in many other icosahedral viruses. Groups of 5 G proteins form 12 dominating spikes that enclose a hydrophilic channel containing some diffuse electron density. Each G protein is a tight β barrel with its strands running radially outwards and with a topology similar to that of the F protein. The 12 'pilot' H proteins per virion may be partially located in the putative ion channel. The small, basic J protein is associated with the DNA and is situated in an interior cleft of the F protein. Tentatively, there are three regions of partially ordered DNA structure, accounting for about 12% of the total genome.Bacteriophage ΦX174 is a small icosahedral virus that contains a single-stranded, closed circular DNA molecule with 5,386 nucleotide bases (for a recent review, see ref. 1). Of the 11 gene products, four (J, F, G and H) participate in the structure of the virion. There are 60 copies each of the J, F and G proteins and 12 copies of the H protein per virion [2][3][4] (Table 1). Electron microscopy of shadowed or negatively stained particles [5][6][7][8] , as well as a threedimensional reconstruction of frozen-hydrated virions (Fig. 1a), clearly show large spikes at the vertices of the icosahedral particles (N.H.O., T.S.B., P.W. and N.L.I., manuscript in preparation). These spikes are about 32 Å long and have a mean diameter of 70 Å. Edgell et al. 3 have shown that these spikes, which can be removed from the capsid with 4 M urea treatment, are composed of G and H proteins. Assuming all 12 spikes are identical, then each spike will contain five G and one H protein 2 . The capsid itself has an external diameter of roughly 260 Å, with a protein shell that is about 30 Å thick, and contains the F and J proteins as well as the single-stranded (ss) DNA. The phage recognizes a lipopolysaccharide (LPS) receptor on the outer cell membrane of Escherichia coli [8][9][10][11] . Host range mutants, which determine which strains of E. coli are infected by ΦX174, map into the F, G and H genes [12][13][14][15] The infectious virion has a relative molecular mass of 6.2 × 10 6 (M r 6,200K) (26% is DNA) 32 . Lysates of infected E. coli contain two components which can be separated by sedimentation through a sucrose gradient 32,33 . The fast band contains the infectious 114S particles whereas the slow band contains noninfectious, 70S particles 32,34,35 . The latter contains about 20% of the normal DNA content with all of the genome represented in the population of particles. Both types of particles can be crystallized into isomorphous monoclinic crystals with space group P2 1 , and cell dimensions a = 305.6, b = 360.8, c = 299.5 Å, β = 92.89° that diffract at least to 2.6-Å resolution 33 . The asymmetric unit of the crystal cell contains one complete particle. We report here the three-dimensional structure...

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Section: Protein Structurementioning

confidence: 99%

Atomic structure of single-stranded DNA bacteriophage ΦX174 and its functional implications

McKenna

Xia

Willingmann

et al. 1992

Nature

217

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“…with coordination number n = 5); the other capsomers are called hexons and they have 6 neighbour capsomers (n = 6). The simple geometrical construction model introduced by Caspar and Klug (CK) 2 to explain the architecture of icosahedral viruses is a milestone in modern virology. Generalizations of the CK rules properly account for the geometry of some exceptional icosahedral capsids [3][4][5][6] and other elongated virus capsids that share coordination numbers with the icosahedral ones [7][8][9] .…”

Section: Introductionmentioning

confidence: 99%

A minimal representation of the self-assembly of virus capsids

2014

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Viruses are biological nanosystems with a capsid of protein-made capsomer units that encloses and protects the genetic material responsible for their replication. Here we show how the geometrical constraints of the capsomer-capsomer interaction in icosahedral capsids fix the form of the shortest and universal truncated multipolar expansion of the two-body interaction between capsomers. The structures of many of the icosahedral and related virus capsids are located as single lowest energy states of this potential energy surface. Our approach unveils relevant features of the natural design of the capsids and can be of interest in fields of nanoscience and nanotechnology where similar hollow convex structures are relevant.

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“…15 The infectious BMV capsid has a triangulation number of T ) 3, which means that there are 180 proteins forming it. Nevertheless, RNA-controlled polymorphism is known to occur.…”

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confidence: 99%

Nanoparticle-Templated Assembly of Viral Protein Cages

et al. 2006

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Self-assembly of regular protein surfaces around nanoparticle templates provides a new class of hybrid biomaterials with potential applications in medical imaging and in bioanalytical sensing. We report here the first example of efficiently self-assembled virus-like particles (VLPs) having a brome mosaic virus protein coat and a functionalized gold core. The present study indicates that functionalized gold particles can initiate VLP assembly by mimicking the electrostatic behavior of the nucleic acid component of the native virus. These VLP constructs are symmetric, with the protein stoichiometry and packaging properties indicating similarity to the icosahedral packing of the capsid. Moreover, a pH-induced swelling transition of the VLPs is observed, in direct analogy to the native virus.Two-dimensional crystalline arrays of proteins self-assembled on flat supports have recently emerged as prime candidates for biotechnological applications. 1,2 Due to their intrinsic symmetry, these arrays can provide high density and equivalent environments for binding domains, characteristics that are difficult to achieve by any other technologies. 3 The ability to engineer specific regulatory switches into proteins by use of recombinant DNA technology also promises additional uses in these arrays.The protein coat, or capsid, of many viruses provides a discrete analogue to extended protein assemblies on planar surfaces. As a consequence, modified-virus capsids have been proposed as versatile biomolecular platforms for displaying engineered peptide sequences for triggering specific host responses. 3,4 Moreover, the regular motif of tubular or quasispherical capsids has been used for the templated synthesis of nanomaterials ranging from magnetic particles 5 to nanowires for electronic applications. 6 The majority of current studies on protein cage-based materials have focused on the use of the capsid surface as a nucleator and/or template for the growth or attachment of inorganic entities. The converse approach of using inorganic particles to nucleate viral capsids represents a new method for synthesizing hybrid inorganic/viral particles, thus widening the range of possible combinations of physical and chemical properties.Preliminary experiments on the encapsulation of functionalized gold nanoparticles into brome mosaic virus (BMV) capsids have shown that the VLP protein coat is likely organized in a closed shell, similar in its physicochemical properties to the native virus. 7,8 These previous examples of nanoparticle encapsidation were characterized by an extremely low yield relative to the formation of empty capsid (∼1%), 9 in stark contrast with the essentially quantitative in-vivo incorporation of the native RNA. 9 Practical application of these systems, however, requires a high yield of homogeneous material. Moreover, knowledge of the VLP shell structure and concomitant preservation of its functional attributes also requires homogeneous materials that can be used for high-resolution structural studies.The fact that...

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Physical Principles in the Construction of Regular Viruses

Cited by 2,246 publications

References 0 publications

Atomic structure of single-stranded DNA bacteriophage ΦX174 and its functional implications

Atomic structure of single-stranded DNA bacteriophage ΦX174 and its functional implications

A minimal representation of the self-assembly of virus capsids

Nanoparticle-Templated Assembly of Viral Protein Cages

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