Multiple Conformational States of the Bacteriophage T4 Capsid Surface Lattice Induced When Expansion Occurs without Prior Cleavage

Kocsis, Eva; Greenstone, Heather L.; Locke, Emily; Kessel, Martin; Steven, Alasdair C.

doi:10.1006/jsbi.1996.3833

Cited by 15 publications

(9 citation statements)

References 35 publications

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“…In the presence of monovalent ions (100 mM NaCl), [pb8p] n capsomeres autoassociate into open tubes of various lengths but have an almost-constant diameter (54 nm) and a thin shell. These tubes are qualified as expanded, considering their diameter and their thin shell as well as by comparison to the morphology of tubes (polyheads) made of gp23, the major head protein of phage T4 (1,21). Very few angular or closed structures are observed, suggesting that the tubes are formed by hexons exclusive of pentons, similarly to the tubes observed in other viral shell assemblies, such as SPO1 (29) and T4 (1, 21).…”

Section: Discussionmentioning

confidence: 99%

In Vitro Assembly of the T=13 Procapsid of Bacteriophage T5 with Its Scaffolding Domain

Huet

Conway

Letellìer

et al. 2010

J Virol

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The Siphoviridae coliphage T5 differs from other members of this family by the size of its genome (121 kbp) and by its large icosahedral capsid (90 nm), which is organized with T‫31؍‬ geometry. T5 does not encode a separate scaffolding protein, but its head protein, pb8, contains a 159-residue aminoterminal scaffolding domain (⌬ domain) that is the mature capsid. We have deciphered the early events of T5 shell assembly starting from purified pb8 with its ⌬ domain (pb8p). The self assembly of pb8p is regulated by salt conditions and leads to structures with distinct morphologies. Expanded tubes are formed in the presence of NaCl, whereas Ca 2؉ promotes the association of pb8p into contracted tubes and procapsids. Procapsids display an angular organization and 20-nm-long internal radial structures identified as the ⌬ domain. The T5 head maturation protease pb11 specifically cleaves the ⌬ domain of contracted and expanded tubes. Ca 2؉ is not required for proteolytic activity but for the organization of the ⌬ domain. Taken together, these data indicate that pb8p carries all of the information in its primary sequence to assemble in vitro without the requirement of the portal and accessory proteins. Furthermore, Ca 2؉ plays a key role in introducing the conformational diversity that permits the formation of a stable procapsid. Phage T5 is the first example of a viral capsid consisting of quasi-equivalent hexamers and pentamers whose assembly can be carried out in vitro, starting from the major head protein with its scaffolding domain, and whose endpoint is an icosahedral T‫31؍‬ particle.

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Section: Discussionmentioning

confidence: 99%

In Vitro Assembly of the T=13 Procapsid of Bacteriophage T5 with Its Scaffolding Domain

Huet

Conway

Letellìer

et al. 2010

J Virol

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“…Uncleaved polyheads may be induced to expand by the relatively mild treatment of exposure to 0.2 M guanidine-HCl, giving rise to a variety of partially expanded structures . 31 Here, also, incomplete expansion was attributed to the trapping of Δ-domains at inter-subunit interfaces. Moreover, it has been shown by immuno-gold electron microscopy that the T4 Δ-domains, if still present, are translocated from the inner to the outer surface in expansion, 32 as we infer to be the case for HK97 (Figures 4(b) and 5(b)).…”

Section: Role Of δ-Domain Cleavage In Facilitating Expansionmentioning

confidence: 94%

A Free Energy Cascade with Locks Drives Assembly and Maturation of Bacteriophage HK97 Capsid

Ross

Conway

Cheng

et al. 2006

Journal of Molecular Biology

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We investigated the thermodynamic basis of HK97 assembly by scanning calorimetry and cryo-electron microscopy. This pathway involves self-assembly of hexamers and pentamers of the precursor capsid protein gp5 into procapsids; proteolysis of their N-terminal Delta-domains; expansion, a major conformational change; and covalent crosslinking. The thermal denaturation parameters convey the changes in stability at successive steps in assembly, and afford estimates of the corresponding changes in free energy. The procapsid represents a kinetically accessible local minimum of free energy. In maturation, it progresses to lower minima in a cascade punctuated by irreversible processes ("locks"), i.e. proteolysis and crosslinking, that lower kinetic barriers and prevent regression. We infer that Delta-domains not only guide assembly but also restrain the procapsid from premature expansion; their removal by proteolysis is conducive to initiating expansion and to its proceeding to completion. We also analyzed the mutant E219K, whose capsomers reassemble in vitro into procapsids with vacant vertices called "whiffleballs". E219K assemblies all have markedly reduced stability compared to wild-type gp5 (DeltaT(p) approximately -7 degrees C to -10 degrees C; where T(p) is the denaturation temperature). As the mutated residue is buried in the core of gp5, we attribute the observed reduction in stability to steric and electrostatic perturbations of the packing of side-chains in the subunit interior. To explain the whiffleball phenotype, we suggest that these effects propagate to the capsomer periphery in such a way as to differentially affect the stability or solubility of dissociated pentamers, leaving only hexamers to reassemble.

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“…In vitro treatment of proheads with denaturants can also trigger maturation, probably through unfolding of the domains that are cleaved by protease in vivo . Maturation intermediates of HK97 proheads and T4 polyheads have been trapped in vitro [115–119]. Head expansion is probably initiated at one end by the portal protein [120] and is then propagated through the prohead.…”

Section: Dsdna Tailed Phagesmentioning

confidence: 99%

Bacteriophage Assembly

Aksyuk

Rossmann

2011

Viruses

120

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Bacteriophages have been a model system to study assembly processes for over half a century. Formation of infectious phage particles involves specific protein-protein and protein-nucleic acid interactions, as well as large conformational changes of assembly precursors. The sequence and molecular mechanisms of phage assembly have been elucidated by a variety of methods. Differences and similarities of assembly processes in several different groups of bacteriophages are discussed in this review. The general principles of phage assembly are applicable to many macromolecular complexes.

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Multiple Conformational States of the Bacteriophage T4 Capsid Surface Lattice Induced When Expansion Occurs without Prior Cleavage

Cited by 15 publications

References 35 publications

In Vitro Assembly of the T=13 Procapsid of Bacteriophage T5 with Its Scaffolding Domain

In Vitro Assembly of the T=13 Procapsid of Bacteriophage T5 with Its Scaffolding Domain

A Free Energy Cascade with Locks Drives Assembly and Maturation of Bacteriophage HK97 Capsid

Bacteriophage Assembly

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