Dataset Information

Global Proteomic Profiling of Salmonella Infection by a Giant Phage.

ABSTRACT: The 240-kb Salmonella phage SPN3US genome encodes 264 gene products, many of which are functionally uncharacterized. We have previously used mass spectrometry to define the proteomes of wild-type and mutant forms of the SPN3US virion. In this study, we sought to determine whether this technique was suitable for the characterization of the SPN3US proteome during liquid infection. Mass spectrometry of SPN3US-infected cells identified 232 SPN3US and 1,994 Salmonella proteins. SPN3US proteins with related functions, such as proteins with roles in DNA replication, transcription, and virion formation, were coordinately expressed in a temporal manner. Mass spectral counts showed the four most abundant SPN3US proteins to be the major capsid protein, two head ejection proteins, and the functionally unassigned protein gp22. This high abundance of gp22 in infected bacteria contrasted with its absence from mature virions, suggesting that it might be the scaffold protein, an essential head morphogenesis protein yet to be identified in giant phages. We identified homologs to SPN3US gp22 in 45 related giant phages, including ?KZ, whose counterpart is also abundant in infected bacteria but absent in the virion. We determined the ?KZ counterpart to be cleaved in vitro by its prohead protease, an event that has been observed to promote head maturation of some other phages. Our findings are consistent with a scaffold protein assignment for SPN3US gp22, although direct evidence is required for its confirmation. These studies demonstrate the power of mass spectral analyses for facilitating the acquisition of new knowledge into the molecular events of viral infection.IMPORTANCE "Giant" phages with genomes >200?kb are being isolated in increasing numbers from a range of environments. With hosts such as Salmonella enterica, Pseudomonas aeruginosa, and Erwinia amylovora, these phages are of interest for phage therapy of multidrug-resistant pathogens. However, our understanding of how these complex phages interact with their hosts is impeded by the proportion (?80%) of their gene products that are functionally uncharacterized. To develop the repertoire of techniques for analysis of phages, we analyzed a liquid infection of Salmonella phage SPN3US (240-kb genome) using third-generation mass spectrometry. We observed the temporal production of phage proteins whose genes collectively represent 96% of the SPN3US genome. These findings demonstrate the sensitivity of mass spectrometry for global proteomic profiling of virus-infected cells, and the identification of a candidate for a major head morphogenesis protein will facilitate further studies into giant phage head assembly.

SUBMITTER: Weintraub ST

PROVIDER: S-EPMC6384053 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature

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Global Proteomic Profiling of Salmonella Infection by a Giant Phage.

Weintraub Susan T ST Mohd Redzuan Nurul Humaira NH Barton Melissa K MK Md Amin Nur Amira NA Desmond Maxim I MI Adams Lily E LE Ali Bazla B Pardo Sammy S Molleur Dana D Wu Weimin W Newcomb William W WW Osier Michael V MV Black Lindsay W LW Steven Alasdair C AC Thomas Julie A JA

Journal of virology 20190219 5

The 240-kb Salmonella phage SPN3US genome encodes 264 gene products, many of which are functionally uncharacterized. We have previously used mass spectrometry to define the proteomes of wild-type and mutant forms of the SPN3US virion. In this study, we sought to determine whether this technique was suitable for the characterization of the SPN3US proteome during liquid infection. Mass spectrometry of SPN3US-infected cells identified 232 SPN3US and 1,994 Salmonella proteins. SPN3US p ...[more]

PMID: 30541839

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Project description:Giant tailed bacterial viruses, or phages, such as Pseudomonas aeruginosa phage ϕKZ, have long genomes packaged into large, atypical virions. Many aspects of ϕKZ and related phage biology are poorly understood, mostly due to the fact that the functions of the majority of their proteins are unknown. We hypothesized that the Salmonella enterica phage SPN3US could be a useful model phage to address this gap in knowledge. The 240-kb SPN3US genome shares a core set of 91 genes with ϕKZ and related phages, ∼61 of which are virion genes, consistent with the expectation that virion complexity is an ancient, conserved feature. Nucleotide sequencing of 18 mutants enabled assignment of 13 genes as essential, information which could not have been determined by sequence-based searches for 11 genes. Proteome analyses of two SPN3US virion protein mutants with knockouts in 64 and 241 provided new insight into the composition and assembly of giant phage heads. The 64 mutant analyses revealed all the genetic determinants required for assembly of the SPN3US head and a likely head-tail joining role for gp64, and its homologs in related phages, due to the tailless-particle phenotype produced. Analyses of the mutation in 241, which encodes an RNA polymerase β subunit, revealed that without this subunit, no other subunits are assembled into the head, and enabled identification of a "missing" β' subunit domain. These findings support SPN3US as an excellent model for giant phage research, laying the groundwork for future analyses of their highly unusual virions, host interactions, and evolution.ImportanceIn recent years, there has been a paradigm shift in virology with the realization that extremely large viruses infecting prokaryotes (giant phages) can be found in many environments. A group of phages related to the prototype giant phage ϕKZ are of great interest due to their virions being among the most complex of prokaryotic viruses and their potential for biocontrol and phage therapy applications. Our understanding of the biology of these phages is limited, as a large proportion of their proteins have not been characterized and/or have been deemed putative without any experimental verification. In this study, we analyzed Salmonella phage SPN3US using a combination of genomics, genetics, and proteomics and in doing so revealed new information regarding giant phage head structure and assembly and virion RNA polymerase composition. Our findings demonstrate the suitability of SPN3US as a model phage for the growing group of phages related to ϕKZ.

Dataset Information

Global Proteomic Profiling of Salmonella Infection by a Giant Phage.

Publications

Global Proteomic Profiling of <i>Salmonella</i> Infection by a Giant Phage.

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