Proteolytic and Conformational Control of Virus Capsid Maturation: The Bacteriophage HK97 System

Conway, James F.; Duda, Robert L.; Cheng, Naiqian; Hendrix, Roger W.; Steven, Alasdair C.

doi:10.1006/jmbi.1995.0538

Cited by 175 publications

(194 citation statements)

References 52 publications

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“…The hexamer-associated portion of the contiguous shell is also markedly altered, having become thinner, smoother, and wider in the plane of the shell. This region does not match the corresponding region of Prohead II (which is essentially the same size as Prohead I, not 10% larger; Conway et al, 1995). However, it is essentially superimposable on the corresponding region of Expansion Intermediate I, the transition state produced by inducing Prohead II to expand at acidic pH .…”

Section: Structure Of Thermally Perturbed Prohead Imentioning

confidence: 83%

“…Maturation commences with activation of the protease and proteolysis of the Δ-domains, producing Prohead II. This particle is primed to undergo a major structural transformation -"expansion" (Conway et al, 1995;Duda et al, 1995b). In vivo, expansion is triggered by DNA packaging, wildtype procapsids having a portal channel for the entry of DNA.…”

Section: Introductionmentioning

confidence: 99%

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A thermally induced phase transition in a viral capsid transforms the hexamers, leaving the pentamers unchanged

Conway

Cheng

Ross

et al. 2007

Journal of Structural Biology

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Scanning calorimetry combined with cryo-electron microscopy affords a powerful approach to investigating hierarchical interactions in multi-protein complexes. Calorimetry can detect the temperatures at which certain interactions are disrupted and cryo-EM can reveal the accompanying structural changes. The procapsid of bacteriophage HK97 (Prohead I) is a 450 Å-diameter shell composed of 60 hexamers and 12 pentamers of gp5, organized with icosahedral symmetry. Gp5 consists of the N-terminal Δ-domain (11 kDa) and gp5* (31 kDa): gp5* forms the contiguous shell from which clusters of Δ-domains extend inwards. At neutral pH, Prohead I exhibits an endothermic transition at 53°C with an enthalpy change of 14 kcal/mol (of gp5 monomer). We show that this transition is reversible. To capture its structural expression, we incubated Prohead I at 60°C followed by rapid freezing and, by cryo-EM, observed a capsid species 10% larger than Prohead I. At 11 Å resolution, visible changes are confined to the gp5 hexamers. Their Δ-domain clusters have disappeared and are presumably disordered, either by unfolding or dispersal. The gp5* hexamer rings are thinned and flattened as they assume the conformation observed in Expansion Intermediate I, a transition state of the normal, proteolysis-induced, maturation pathway. We infer that, at ambient temperatures, the hexamer Δ-domains restrain their gp5* rings from switching to a lower free energy, EI-I-like, state; above 53°, this constraint is overcome. Pentamers, on the other hand, are more stably anchored and resist this thermal perturbation. KeywordsDifferential scanning calorimetry; cryo-electron microscopy; virus capsid structure; bacteriophage HK97; conformational changes "All capsomers are quasi-equivalent but some capsomers are more quasi-equivalent than others." -after G. Orwell, Animal Farm.

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Section: Structure Of Thermally Perturbed Prohead Imentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

A thermally induced phase transition in a viral capsid transforms the hexamers, leaving the pentamers unchanged

Conway

Cheng

Ross

et al. 2007

Journal of Structural Biology

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“…The latter process involves significant conformational changes in the proteins assembled into the shell, often leading to a remarkable procapsid expansion transition for many viruses. The expansion is followed by the shell stabilization using three basic mechanisms: in some such as HK97 procapsid expansion is accompanied by the formation of a network of covalent crosslinks 10,30,31 19 , and the eukaryotic herpesviruses incorporate accessory proteins into the shell. In the case of bacteriophage lambda, the maturation process comprises three distinct shell structures: procapsid, expanded capsid and gpD-decorated capsid (Fig.…”

Section: Discussionmentioning

confidence: 99%

Cementing proteins provide extra mechanical stabilization to viral cages

et al. 2014

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The study of virus shell stability is key not only for gaining insights into viral biological cycles but also for using viral capsids in materials science. The strength of viral particles depends profoundly on their structural changes occurring during maturation, whose final step often requires the specific binding of 'decoration' proteins (such as gpD in bacteriophage lambda) to the viral shell. Here we characterize the mechanical stability of gpD-free and gpD-decorated bacteriophage lambda capsids. The incorporation of gpD into the lambda shell imparts a major mechanical reinforcement that resists punctual deformations. We further interrogate lambda particle stability with molecular fatigue experiments that resemble the sub-lethal Brownian collisions of virus shells with macromolecules in crowded environments. Decorated particles are especially robust against collisions of a few k B T (where k B is the Boltzmann's constant and T is the temperature B300 K), which approximate those anticipated from molecular insults in the environment.

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“…The PFT method appears to have no orientation bias and we have repeatedly found that this method correctly identifies a high percentage of particles that would have been rejected in a Common Lines analysis (data not shown). In addition, the Modified Common Lines and PFT methods are better able than Common Lines to discriminate between the relative handedness of the projection images obtained from different particles (e.g., Conway et al, 1995).…”

Section: Pft Methodsmentioning

confidence: 99%

A Model-Based Approach for Determining Orientations of Biological Macromolecules Imaged by Cryoelectron Microscopy

Baker

Cheng

1996

Journal of Structural Biology

362

226

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Proteolytic and Conformational Control of Virus Capsid Maturation: The Bacteriophage HK97 System

Cited by 175 publications

References 52 publications

A thermally induced phase transition in a viral capsid transforms the hexamers, leaving the pentamers unchanged

A thermally induced phase transition in a viral capsid transforms the hexamers, leaving the pentamers unchanged

Cementing proteins provide extra mechanical stabilization to viral cages

A Model-Based Approach for Determining Orientations of Biological Macromolecules Imaged by Cryoelectron Microscopy

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