Is phage DNA ‘injected’ into cells—biologists and physicists can agree

Grayson, Paul; Molineux, Ian J.

doi:10.1016/j.mib.2007.04.004

Cited by 66 publications

(76 citation statements)

References 71 publications

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“…Initially driven by the high pressure of DNA inside the phage head, release of linear double-stranded DNA from the particles is expected to slow down, so that the essentially complete release observed here on the time scale of the experiment may be due to solvent drag acting on the highly viscous DNA and Brownian motion of the particles. Pressure-induced ejection was observed for different phages like T5 (18) and (14), although complete DNA translocation during infection is likely driven by other mechanisms like diffusion, enzyme activity, or protein binding, and even osmotic gradients might contribute to the intrusion of DNA into the host cell (32,46,47). In the case of phage T7, ejection proteins have been proposed to build an extensible tail that supports the enzyme-driven transport of phage DNA across the two membranes into Gram-negative cells (48).…”

Section: Discussionmentioning

confidence: 99%

Tailspike Interactions with Lipopolysaccharide Effect DNA Ejection from Phage P22 Particles in Vitro

Andres¹,

Hanke

Baxa³

et al. 2010

Journal of Biological Chemistry

138

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Initial attachment of bacteriophage P22 to the Salmonella host cell is known to be mediated by interactions between lipopolysaccharide (LPS) and the phage tailspike proteins (TSP), but the events that subsequently lead to DNA injection into the bacterium are unknown. We used the binding of a fluorescent dye and DNA accessibility to DNase and restriction enzymes to analyze DNA ejection from phage particles in vitro. Ejection was specifically triggered by aggregates of purified Salmonella LPS but not by LPS with different O-antigen structure, by lipid A, phospholipids, or soluble O-antigen polysaccharide. This suggests that P22 does not use a secondary receptor at the bacterial outer membrane surface. Using phage particles reconstituted with purified mutant TSP in vitro, we found that the endorhamnosidase activity of TSP degrading the O-antigen polysaccharide was required prior to DNA ejection in vitro and DNA replication in vivo. If, however, LPS was pre-digested with soluble TSP, it was no longer able to trigger DNA ejection, even though it still contained five O-antigen oligosaccharide repeats. Together with known data on the structure of LPS and phage P22, our results suggest a molecular model. In this model, tailspikes position the phage particles on the outer membrane surface for DNA ejection. They force gp26, the central needle and plug protein of the phage tail machine, through the core oligosaccharide layer and into the hydrophobic portion of the outer membrane, leading to refolding of the gp26 lazo-domain, release of the plug, and ejection of DNA and pilot proteins.

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Section: Discussionmentioning

confidence: 99%

Tailspike Interactions with Lipopolysaccharide Effect DNA Ejection from Phage P22 Particles in Vitro

Andres¹,

Hanke

Baxa³

et al. 2010

Journal of Biological Chemistry

138

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“…The precise molecular mechanism of transfer of a dsDNA molecule from bacteriophages to the host cells is still not fully understood [1,2]. The major steps comprised of recognition of proteins of the host by the phage, activation of the release of DNA from the lumen of the phage, and the eventual translocation of DNA into the host cell have been well recognized in the literature [3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Langevin dynamics simulation of DNA ejection from a phage

2013

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We have performed Langevin dynamics simulations of a coarse-grained model of ejection of dsDNA from 29 phage. Our simulation results show significant variations in the local ejection speed, consistent with experimental observations reported in the literature for both in vivo and in vitro systems. In efforts to understand the origin of such variations in the local speed of ejection, we have investigated the correlations between the local ejection kinetics and the packaged structures created at various motor forces and chain flexibility. At lower motor forces, the packaged DNA length is shorter with better organization. On the other hand, at higher motor forces typical of realistic situations, the DNA organization inside the capsid suffers from significant orientational disorder, but yet with long orientational correlation times. This in turn leads to lack of registry between the direction of the DNA segments just to be ejected and the direction of exit. As a result, a significant amount of momentum transfer is required locally for successful exit. Consequently, the DNA ejection temporarily slows down exhibiting pauses. This slowing down occurs at random times during the ejection process, completely determined by the particular starting conformation created by prescribed motor forces. In order to augment our inference, we have additionally investigated the ejection of chains with deliberately changed persistence length. For less inflexible chains, the demand on the occurrence of large momentum transfer for successful ejection is weaker, resulting in more uniform ejection kinetics. While being consistent with experimental observations, our results show the nonergodic nature of the ejection kinetics and call for better theoretical models to portray the kinetics of genome ejection from phages.

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“…Equation (11) shows that the rate of DNA ejection is enhanced, irrespective of the osmotic pressure difference between the capsid and the bacterium; the driving force behind this enhancement is the hydrodynamic drag of water on the DNA in the tail tube, while the source of free energy is the osmotic imbalance between the bacterium and its environment [19][20][21].…”

Section: Hydrodynamic Model For In Vivo Ejectionmentioning

confidence: 99%

“…To date, the hydrodynamic model has remained relatively qualitative [20,21]. The purpose of the present article is to present a simple explicit formulation of the model that retains its key physical ingredients.…”

Section: Introductionmentioning

confidence: 99%

Role of osmotic and hydrostatic pressures in bacteriophage genome ejection

2013

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A critical step in the bacteriophage life cycle is genome ejection into host bacteria. The ejection process for double-stranded DNA phages has been studied thoroughly in vitro, where after triggering with the cellular receptor the genome ejects into a buffer. The experimental data have been interpreted in terms of the decrease in free energy of the densely packed DNA associated with genome ejection. Here we detail a simple model of genome ejection in terms of the hydrostatic and osmotic pressures inside the phage, a bacterium, and a buffer solution or culture medium. We argue that the hydrodynamic flow associated with the water movement from the buffer solution into the phage capsid and further drainage into the bacterial cytoplasm, driven by the osmotic gradient between the bacterial cytoplasm and culture medium, provides an alternative mechanism for phage genome ejection in vivo; the mechanism is perfectly consistent with phage genome ejection in vitro.

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Is phage DNA ‘injected’ into cells—biologists and physicists can agree

Cited by 66 publications

References 71 publications

Tailspike Interactions with Lipopolysaccharide Effect DNA Ejection from Phage P22 Particles in Vitro

Tailspike Interactions with Lipopolysaccharide Effect DNA Ejection from Phage P22 Particles in Vitro

Langevin dynamics simulation of DNA ejection from a phage

Role of osmotic and hydrostatic pressures in bacteriophage genome ejection

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