The transformation of τ particles into t4 heads. II. Transformations of the surface lattice an related observations on form determination

Aebi, Ueli; Bijlenga, R.K.L.; Broek, J. v. d.; Broek, R. van den; Eiserling, Frederick A.; Kellenberger, Colleen A.; Kellenberger, E.; Mesyanzhinov, Vadim V.; Müller, Lucas O.; Showe, Michael K.; Smith, PR; Steven, Alasdair C.

doi:10.1002/jss.400020218

Cited by 93 publications

(55 citation statements)

References 33 publications

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“…Measurements suggest that p20 is an integral part of the capsid and that there are about 12 molecules (31). This number does not increase in giant-headed phages, suggesting that p20 is located in the hemispherical caps (32).…”

Section: J and K)mentioning

confidence: 98%

DNA packaging and the pathway of bacteriophage T4 head assembly.

Hsiao¹,

Black²

1977

Proc. Natl. Acad. Sci. U.S.A.

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A cold-sensitive mutation in the structural gene for a minor phage T4 capsid protein (p20) leads to formation of heads containing p20 and cleaved head proteins and empty of DNA. Such heads can be filled with DNA and converted to active phages in vivo upon shift to high temperature. It appears that p20 has two distinct roles in head assembly: first, in construction of the prehead shell (blocked by ts and am mutation) and, second, in DNA packaging (blocked by cs mutation). The latter function is closely associated with gene 17 product, previously known to be required for DNA packaging. Temperature shift studies of cs-s double mutants and other observations allow determination of phage functions required for DNA packaging. Contrary to previous proposals, we find that T4 DNA packaging is not directly coupled to and can follow DNA synthesis, protein cleavage, prehead core removal, and gene 21-mediated cleavage-induced increase in head volume. Our evidence suggests that an altered head assembly pathway exists and that DNA packaging is probably initiated by DNA-capsid (p20) (p23) (5). In this paper we present evidence suggesting that neither of these pathways is correct. The evidence is also against the proposal that filling of T4 heads with DNA depends upon concurrent DNA synthesis (6).These questions are important because they relate to the function of protein cleavage in virus assembly and the unknown mechanism of DNA condensation. It was initially thought that basic DNA-binding internal proteins of the mature head might condense the DNA, but these proteins proved to be nonessential (1, 7). It was then proposed that DNA packaging was coupled to cleavage of core proteins, so that the generation of acidic internal peptide core remnants might cause repulsive collapse to {-like DNA (8, 9). Similarly, packaging could be coupled to exit of core proteins from the prehead in phages lacking protein processing (10). Another general idea is that packaging is coupled to the expansion of the capsid shell which accompanies protein processing and head filling (11, 12).In this paper we characterize a cold-sensitive (cs Fig. 4k) and was not associated with polyhead production, but gave rise to empty head structures (Fig. 1). The phenotype of this cs2O mutation is similar to that of gene 17 mutations. Indeed, the cs20 mutation and gene 17 function appear very closely interrelated because of (i) similar morphological phenotypes (empty head and ghost production); (ii) accumulation of similar sized concatameric T4 DNA (unpublished); (iii) Thin sections of bacteria infected with cs20 at nonpermissive temperature reveal many empty heads in the interior of the cell (Fig. 1). These clearly differ from the protein core-containing membrane-associated Tau-particles which are also seen in small numbers and are known to be intermediates in head formation (2, 19). The cs20 heads appear to be empty of DNA or core material, and to be of roughly the same size as the occasional head fully packaged with DNA seen in growth under slightly le...

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Section: J and K)mentioning

confidence: 98%

DNA packaging and the pathway of bacteriophage T4 head assembly.

Hsiao¹,

Black²

1977

Proc. Natl. Acad. Sci. U.S.A.

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“…Each prolate head consists of two icosahedral (half T=3) caps separated by an equatorial band of 10 hexamers for a total of 30 hexamers compared to 20 in the isometric particles ( Figures 2K and 2L). These prolate particles are described by the elongation number Q=5, from which the number of subunits (240) may be calculated by the relation 30(T+Q) (Aebi et al, 1974). However, because the connector replaces five subunits at the portal vertex, the predicted number of gp8 subunits is 235.…”

Section: The Prolate Headmentioning

confidence: 99%

Assembly of a Tailed Bacterial Virus and Its Genome Release Studied in Three Dimensions

Tao¹,

Olson²,

Wang³

et al. 2014

Selected Papers of Michael G Rossmann With Commentaries

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SummaryWe present the first three-dimensional reconstruction of a prolate, tailed phage, and its empty prohead precursor by cryo-electron microscopy. The head-tail connector, the central component of the DNA packaging machine, is visualized for the first time in situ within the Bacillus subtilis dsDNA phage ϕ29. The connector, with 12-or 13-fold symmetry, appears to fit loosely into a pentameric vertex of the head, a symmetry mismatch that may be required to rotate the connector to package DNA. The prolate head of ϕ29 has 10 hexameric units in its cylindrical equatorial region, and 11 pentameric and 20 hexameric units comprise icosahedral end-caps with T=3 quasisymmetry. Reconstruction of an emptied phage particle shows that the connector and neck/tail assembly undergo significant conformational changes upon ejection of DNA.

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“…Isometric icosahedral capsids require only a few variations in subunit conformation, the number being given by the triangulation number, T. The capsid contains 60 copies of each conformer. One generalization of the icosahedral design, as in bacteriophages T4 [1] and f29 [40], involves extension along an axis of symmetry -the 5-fold axis in the case of T4, whereby the point group symmetry is reduced from 5-3-2 to 5-2. The number of quasi-equivalent conformations is given by T þ Q, where Q is the triangulation number of a facet in the elongated mid-section -e.g.…”

Section: Polymorphism and Conformational Variabilitymentioning

confidence: 99%

“…The number of quasi-equivalent conformations is given by T þ Q, where Q is the triangulation number of a facet in the elongated mid-section -e.g. T ¼ 13 [1] and Q ¼ 20 [14] for T4. For most viruses, the T-number is a uniquely defined and evolutionarily robust parameter, although there are exceptions such as hepatitis B virus which produces capsids of both T ¼ 3 and T ¼ 4 [39], and the bacteriophage P2/P4 system which produces capsids of T ¼ 4 and T ¼ 7 [13].…”

Section: Polymorphism and Conformational Variabilitymentioning

confidence: 99%

Irregular and Semi‐Regular Polyhedral Models for Rous Sarcoma Virus Cores

Heymann

Butan

Winkler

et al. 2000

Computational and Mathematical Methods in Medicine

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Whereas many viruses have capsids of uniquely defined sizes that observe icosahedral symmetry, retrovirus capsids are highly polymorphic. Nevertheless, they may also be described as polyhedral foldings of a fullerene lattice on which the capsid protein (CA) is arrayed. Lacking the high order of symmetry that facilitates the reconstruction of icosahedral capsids from cryo-electron micrographs, the 3D structures of individual retrovirus capsids may be determined by cryoelectron tomography, albeit at lower resolution. Here, we describe computational and graphical methods used to construct polyhedral models that match in size and shape, capsids of Rous sarcoma virus (RSV) observed within intact virions. The capsids fall into several shape classes, including tubes, 'lozenges' and 'coffins'. The extent to which a capsid departs from icosahedral symmetry reflects the irregularity of the distribution of pentamers, which are always 12 in number for a closed polyhedral capsid. The number of geometrically distinct polyhedra grows rapidly with increasing quotas of hexamers, and ranks in the millions for particles in the size range of RSV capsids, which typically have 150-300 hexamers. Unlike the CAs of icosahedral viruses that assume a minimal number of quasi-equivalent conformations equal to the triangulation number (T), retroviral CAs exhibit a near-continuum of quasi-equivalent conformations -a property that may be attributed to the flexible hinge linking the N-and C-terminal domains.

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The transformation of τ particles into t4 heads. II. Transformations of the surface lattice an related observations on form determination

Cited by 93 publications

References 33 publications

DNA packaging and the pathway of bacteriophage T4 head assembly.

DNA packaging and the pathway of bacteriophage T4 head assembly.

Assembly of a Tailed Bacterial Virus and Its Genome Release Studied in Three Dimensions

Irregular and Semi‐Regular Polyhedral Models for Rous Sarcoma Virus Cores

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