Evaluating the role of phage-shock protein A in Burkholderia pseudomallei

Abstract

The phage-shock protein (Psp) response is an extracytoplasmic response system that is vital for maintenance of the cytoplasmic membrane when the cell encounters stressful conditions. The paradigm of the Psp response has been established in Escherichia coli. The response has been shown to be important for survival during the stationary phase, maintenance of the proton motive force across membranes and implicated in virulence. In this study, we identified a putative PspA homologue in Burkholderia pseudomallei, annotated as BPSL2105. Similar to the induction of PspA in E. coli, the expression of B. pseudomallei BPSL2105 was induced by heat shock. Deletion of BPSL2105 resulted in a survival defect in the late stationary phase coincident with dramatic changes in the pH of the culture medium. The B. pseudomallei BPSL2105 deletion mutant also displayed reduced survival in macrophage infection – the first indication that the Psp response plays a role during intracellular pathogenesis in this species. The purified protein formed large oligomeric structures similar to those observed for the PspA protein of E. coli, and PspA homologues in Bacillus, cyanobacteria and higher plants, providing further evidence to support the identification of BPSL2105 as a PspA-like protein in B. pseudomallei.

Rv2744c Is a PspA Ortholog That Regulates Lipid Droplet Homeostasis and Nonreplicating Persistence in Mycobacterium tuberculosis

“…When imaged by negative-stain electron microscopy, Rv2744c assumed a spheroid-like structure and elongated filamentous-like superstructures that likely consist of stacked spheroidal subunits. These structural characteristics are consistent with those observed with other PspA proteins (42,47,51) and indicate that Rv2744c is a bona fide ortholog of PspA.…”

“…2D and E). These structures strongly resembled those seen with other characterized PspA family members (51,52). Collectively, these data, along with the bioinformatic studies, suggest that Rv2744c possesses structural and physical characteristics consistent with its designation as a PspA family member.…”

“…A common characteristic of PspA family members is their ability to homo-oligomerize and form structured complexes of high molecular weight (42,(50)(51)(52). E. coli PspA forms a 36-mer spheroid-like homo-oligomeric complex consisting of 4 stacked rings of PspA 9-mers (42).…”

“…E. coli PspA forms a 36-mer spheroid-like homo-oligomeric complex consisting of 4 stacked rings of PspA 9-mers (42). Similarly, PspA from Burkholderia pseudomallei homo-oligomerizes to form ringshaped complexes, rod-like species of various lengths, and meshlike structures (51). As M. tuberculosis Rv2744c interacts with itself in vivo (31), we next determined whether Rv2744c also formed homo-oligomeric complexes in vitro.…”

The Phage Shock Protein Response

“…Furthermore, S. Typhimurium and Shigella flexneri psp gene expression are highly induced during macrophage infection, although it is not known if the S. flexneri Psp system is required for virulence (26,61). Deletion of a gene encoding a PspA homolog in Burkholderia pseudomallei reduced survival in macrophages, strongly suggesting that it impacts virulence (87). Finally, a PspA family member in Mycobacterium tuberculosis has been linked to envelope stress and shown to be part of a four-gene operon that might have functional similarities to the Psp response (18,102).…”