Cryo-EM Elucidation of the Structure of Bacteriophage P22 Virions after Genome Release

Abstract

Genome ejection proteins are required to facilitate transport of bacteriophage P22 double-stranded DNA safely through membranes of Salmonella. The structures and locations of all proteins in the context of the mature virion are known, with the exception of three ejection proteins. Furthermore, the changes that occur to the proteins residing in the mature virion upon DNA release are not fully understood. We used cryogenic electron microscopy to obtain what is, to our knowledge, the first asymmetric reconstruction of mature bacteriophage P22 after double-stranded DNA has been extruded from the capsid-a state representative of one step during viral infection. Results of icosahedral and asymmetric reconstructions at estimated resolutions of 7.8 and 12.5 Å resolutions, respectively, are presented. The reconstruction shows tube-like protein density extending from the center of the tail assembly. The portal protein does not revert to the more contracted, procapsid state, but instead maintains an extended and splayed barrel structure. These structural details contribute to our understanding of the molecular mechanism of P22 phage infection and also set the foundation for future exploitation serving engineering purposes.

Structural Analysis of Jumbo Coliphage phAPEC6

“…In the isosurface view of the tail part, one can notice the presence of a lipid patch containing probably the bacterial receptor (arrow in Figure 4B). This kind of structure has already been observed for other phages like P2 [33]. In the 3D reconstruction at a high contour level ( Figure 5D), visualization of this small membrane piece is possible.…”

Structures of Echovirus 30 in complex with its receptors inform a rational prediction for enterovirus receptor usage

“…Generally, the standard verification of a bona fide viral receptor involves a number of assays, such as that expression of this receptor enables normally unsusceptible cell lines to support viral propagation; loss of expression of this receptor or its binding partner (e.g., antibodies) renders cells resistant to viral infection; soluble receptor could directly bind viral particles and neutralizes infection, but these assays are timeconsuming. By contrast, the recent 'resolution revolution' in cryo-EM has accelerated the process for determining high-resolution structures of a wide array of previously intractable biological systems [52][53][54][55][56][57][58] . In this study, we provided models for E30 in complex with its receptors CD55 and FcRn and systematically analyzed available human EVs-receptor interactions, which pinpointed key structure-receptor usage correlates.…”

In Vitro Studies of Lipopolysaccharide-Mediated DNA Release of Podovirus HK620

“…Although they cannot show how phage proteins and genetic material enter the cytosol of a living bacterial cell, they provide a reductionist approach to the mechanisms in the bacteriophage infection machine. In vivo, to transport its DNA over all parts of the gram-negative cell envelope, P22 particles extend their tails to form tubular structures, as found in other gram-negative-specific phages [ 45 , 46 , 47 ]. These extensions at the tip of the tail are most probably formed by P22 ejection proteins that must leave the particle at an early time point after opening.…”