Conformational Changes Leading to T7 DNA Delivery upon Interaction with the Bacterial Receptor

Abstract

Background: T7 bacteriophage infects E. coli bacteria; during this process, the tail recognizes the bacterial receptor. Results: Interactions of T7 with rough LPS trigger DNA delivery by promoting changes in the tail tube. Conclusion: E. coli rough LPS act as the receptor in vitro for T7 bacteriophage. Significance: Biotechnological application of bacteriophages as antibacterial agents demands detailed molecular knowledge of bacteriophage infection.

Characterization of the initial steps in the T7 DNA ejection process

“…1A), while the incubation with smooth LPS did not affect the DNA content of T7 particles. 11 These results suggested that the inactivation of T7 was due to the release of DNA from the virus capsid triggered by the interaction of the T7 particle with purified rough LPS.…”

“…16 The fact that these processes also take place after interaction of T7 viral particles with purified rough LPS in vitro suggests that this single interaction is able to mimic the main steps of the DNA ejection process during T7 infection of E. coli. Based on these assumptions, Gonzalez-Garcia et al 11 performed a series of in vitro assays to follow DNA ejection rates, and to determine the virus-LPS interaction con- 17 It is interesting to note that the slower Podoviridae DNA release kinetics, as compared with other virus of the Siphoviridae family, 17 might be caused by the simultaneous translocation of the internal core proteins together with the DNA in the case of Podoviridae.…”

“…1B), suggesting that the triggering of the DNA release caused the core to disassemble and the core proteins to be proteolyzed. 11 The simultaneous release of DNA and disappearance of the core proteins from the T7 viral particles is characteristic of the infection process in vivo. 16 The fact that these processes also take place after interaction of T7 viral particles with purified rough LPS in vitro suggests that this single interaction is able to mimic the main steps of the DNA ejection process during T7 infection of E. coli.…”

“…It has been proposed since a long time that certain bacteriophages might interact with a subclass of LPS known as rough LPS, which are lacking the outermost O antigen domain. 8,14 Gonzalez-Garc ıa et al 11 carried out the incubation of T7 with purified rough LPS, and found that the virions were inactivated. Analysis by electron microscopy of T7 incubated with rough LPS revealed that the viral particles had lost the packaged DNA, and they were empty (Fig.…”

“…Although some studies had pointed out the capability of rough LPS to neutralize T7 8,12 their role was defined mainly as a primary phage receptor that mediated reversible binding to the bacterial surface, while another secondary receptor was suspected to be essential for irreversible binding and infection. 7,13 In their work, Gonz alezGarc ıa et al 11 used biochemical assays together with cryo-EM and image processing to characterize the T7 ejection reaction triggered by rough LPS. Their studies allowed to describe the conformational changes that take place in the tail complex during DNA exit and to hypothesize a possible schema of the early steps followed by the virus during infection.…”