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Role of the periplasmic chaperones Skp, SurA, and DegQ in outer membrane protein biogenesis in Neisseria meningitidis.

ABSTRACT: The periplasmic chaperones Skp, SurA, and DegP are implicated in the biogenesis of outer membrane proteins (OMPs) in Escherichia coli. Here, we investigated whether these chaperones exert similar functions in Neisseria meningitidis. Although N. meningitidis does not contain a homolog of the protease/chaperone DegP, it does possess a homolog of another E. coli protein, DegQ, which can functionally replace DegP when overproduced. Hence, we examined whether in N. meningitidis, DegQ acts as a functional homolog of DegP. Single skp, surA, and degQ mutants were easily obtained, showing that none of these chaperones is essential in N. meningitidis. Furthermore, all combinations of double mutants were generated and no synthetic lethality was observed. The absence of SurA or DegQ did not affect OMP biogenesis. In contrast, the absence of Skp resulted in severely lower levels of the porins PorA and PorB but not of other OMPs. These decreased levels were not due to proteolytic activity of DegQ, since porin levels remained low in a skp degQ double mutant, indicating that neisserial DegQ is not a functional homolog of E. coli DegP. The absence of Skp resulted in lower expression of the porB gene, as shown by using a P(porB)-lacZ fusion. We found no cross-species complementation when Skp of E. coli or N. meningitidis was heterologously expressed in skp mutants, indicating that Skp functions in a species-specific manner. Our results demonstrate an important role for Skp but not for SurA or DegQ in OMP biogenesis in N. meningitidis.

SUBMITTER: Volokhina EB

PROVIDER: S-EPMC3067652 | biostudies-literature | 2011 Apr

REPOSITORIES: biostudies-literature

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Role of the periplasmic chaperones Skp, SurA, and DegQ in outer membrane protein biogenesis in Neisseria meningitidis.

Volokhina Elena B EB Grijpstra Jan J Stork Michiel M Schilders Ingrid I Tommassen Jan J Bos Martine P MP

Journal of bacteriology 20110204 7

The periplasmic chaperones Skp, SurA, and DegP are implicated in the biogenesis of outer membrane proteins (OMPs) in Escherichia coli. Here, we investigated whether these chaperones exert similar functions in Neisseria meningitidis. Although N. meningitidis does not contain a homolog of the protease/chaperone DegP, it does possess a homolog of another E. coli protein, DegQ, which can functionally replace DegP when overproduced. Hence, we examined whether in N. meningitidis, DegQ acts as a functi ...[more]

PMID: 21296967

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Project description:The outer membrane (OM) of Gram-negative bacteria efficiently protects from harmful environmental stresses such as antibiotics, disinfectants, or dryness. The main constituents of the OM are integral OM β-barrel proteins (OMPs). In Gram-negative bacteria such as Escherichia coli, Yersinia enterocolitica, and Pseudomonas aeruginosa, the insertion of OMPs depends on a sophisticated biogenesis pathway. This comprises the SecYEG translocon, which enables inner membrane (IM) passage; the chaperones SurA, Skp, and DegP, which facilitate the passage of β-barrel OMPs through the periplasm; and the β-barrel assembly machinery (BAM), which facilitates insertion into the OM. In E. coli, Y. enterocolitica, and P. aeruginosa, the deletion of SurA is particularly detrimental and leads to a loss of OM integrity, sensitization to antibiotic treatment, and reduced virulence. In search of targets that could be exploited to develop compounds that interfere with OM integrity in Acinetobacter baumannii, we employed the multidrug-resistant strain AB5075 to generate single gene knockout strains lacking individual periplasmic chaperones. In contrast to E. coli, Y. enterocolitica, and P. aeruginosa, AB5075 tolerates the lack of SurA, Skp, or DegP with only weak mutant phenotypes. While the double knockout strains ΔsurAΔskp and ΔsurAΔdegP are conditionally lethal in E. coli, all double deletions were well tolerated by AB5075. Strikingly, even a triple-knockout strain of AB5075, lacking surA, skp, and degP, was viable. IMPORTANCE Acinetobacter baumannii is a major threat to human health due to its ability to persist in the hospital environment, resistance to antibiotic treatment, and ability to deploy multiple and redundant virulence factors. In a rising number of cases, infections with multidrug-resistant A. baumannii end up fatally, because all antibiotic treatment options fail. Thus, novel targets have to be identified and alternative therapeutics have to be developed. The knockout of periplasmic chaperones has previously proven to significantly reduce virulence and even break antibiotic resistance in other Gram-negative pathogens. Our study in A. baumannii demonstrates how variable the importance of the periplasmic chaperones SurA, Skp, and DegP can be and suggests the existence of mechanisms allowing A. baumannii to cope with the lack of the three periplasmic chaperones.

Project description:The bacterial pathogen Helicobacter pylori is capable of colonizing the gastric mucosa of the human stomach using a variety of factors associated with or secreted from its outer membrane (OM). Lipopolysaccharide (LPS) and numerous OM proteins have been shown to be involved in adhesion and immune stimulation/evasion. Many of these factors are essential for colonization and/or pathogenesis in a variety of animal models. Despite this wide array of potential targets present on the bacterial surface, the ability of H. pylori to vary its OM profile limits the effectiveness of vaccines or therapeutics that target any single one of these components. However, it has become evident that the proteins comprising the complexes that transport the majority of these molecules to the OM are highly conserved and often essential. The field of membrane biogenesis has progressed remarkably in the last few years, and the possibility now exists for targeting the mechanisms by which ?-barrel proteins, lipoproteins, and LPS are transported to the OM, resulting in loss of bacterial fitness and significant altering of membrane permeability. In this review, the OM transport machinery for LPS, lipoproteins, and outer membrane proteins (OMPs) are discussed. While the principal investigations of these transport mechanisms have been conducted in Escherichia coli and Neisseria meningitidis, here these systems will be presented in the genetic context of ? proteobacteria. Bioinformatic analysis reveals that minimalist genomes, such as that of Helicobacter pylori, offer insight into the smallest number of components required for these essential pathways to function. Interestingly, in the majority of ? proteobacteria, while the inner and OM associated apparatus of LPS, lipoprotein, and OMP transport pathways appear to all be intact, most of the components associated with the periplasmic compartment are either missing or are almost unrecognizable when compared to their E. coli counterparts. Eventual targeting of these pathways would have the net effect of severely limiting the delivery/transport of components to the OM and preventing the bacterium's ability to infect its human host.

Dataset Information

Role of the periplasmic chaperones Skp, SurA, and DegQ in outer membrane protein biogenesis in Neisseria meningitidis.

Publications

Role of the periplasmic chaperones Skp, SurA, and DegQ in outer membrane protein biogenesis in Neisseria meningitidis.

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