Structural Basis and Kinetics of DsbD-Dependent Cytochrome c Maturation

Stirnimann, Christian U.; Rozhkova, Anna; Grauschopf, Ulla; Grütter, Markus G.; Glockshuber, Rudi; Capitani, Guido

doi:10.1016/j.str.2005.04.014

Cited by 76 publications

(95 citation statements)

References 47 publications

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“…The simplest explanation for this observation is that iron chelation is a common component of the Cpx-inducing signal. Disruptions in disulfide bond formation in the periplasm (expected in the presence of diamide, a dsbD mutation, or CuSO 4 [24]) lead to defects in the ligation of iron-containing heme B to apocytochrome c (86)(87)(88). V. cholerae is predicted to have 14 ctype cytochromes in the cell envelope (89).…”

Section: Discussionmentioning

confidence: 99%

The Vibrio cholerae Cpx Envelope Stress Response Senses and Mediates Adaptation to Low Iron

2014

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The Cpx pathway, a two-component system that employs the sensor histidine kinase CpxA and the response regulator CpxR, regulates crucial envelope stress responses across bacterial species and affects antibiotic resistance. To characterize the CpxR regulon in Vibrio cholerae, the transcriptional profile of the pandemic V. cholerae El Tor C6706 strain was examined upon overexpression of cpxR. Our data show that the Cpx regulon of V. cholerae is enriched in genes encoding membrane-localized and transport proteins, including a large number of genes known or predicted to be iron regulated. Activation of the Cpx pathway further led to the expression of TolC, the major outer membrane pore, and of components of two RND efflux systems in V. cholerae. We show that iron chelation, toxic compounds, or deletion of specific RND efflux components leads to Cpx pathway activation. Furthermore, mutations that eliminate the Cpx response or members of its regulon result in growth phenotypes in the presence of these inducers that, together with Cpx pathway activation, are partially suppressed by iron. Cumulatively, our results suggest that a major function of the Cpx response in V. cholerae is to mediate adaptation to envelope perturbations caused by toxic compounds and the depletion of iron. Perturbations of the bacterial cell envelope can induce cell envelope stress responses. During this process, signal transduction pathways, such as two-component systems (TCS), are necessary for transducing the information from the cell envelope to the cytoplasm for gene expression regulation (1). TCS are the most prevalent signaling pathways in bacteria, and they are involved in the responses to different inducing cues, mainly related to stress responses and environmental changes (2). The Cpx envelope stress response is an example of a TCS and is composed of the sensor histidine kinase CpxA and the response regulator CpxR (3). This system senses envelope stress and regulates the expression of genes involved in maintaining cell envelope homeostasis to increase bacterial survival under adverse conditions (4).CpxA is an inner membrane (IM) protein that autophosphorylates upon detecting an inducing cue and then becomes a phosphodonor and transfers a phosphoryl group to a conserved aspartate of its response regulator, CpxR (3, 5). CpxR phosphorylation leads to the alteration in transcription of multiple genes by the direct binding of CpxR to DNA (5, 6). In addition, CpxR phosphorylation is modulated indirectly by a periplasmic protein, CpxP, which reduces CpxA activity (6, 7) through a possible direct interaction with the periplasmic sensing domain of CpxA (8-11).The Cpx system in Escherichia coli senses misfolded proteins in the bacterial cell envelope and regulates protein folding and degrading factors, such as DegP, DsbA, and PpiD, involved in the alleviation of the envelope stress (12-15). For example, some of the inducing cues of this pathway are aggregated uropathogenic E. coli P pilus subunits and subunits of the enteropathogenic E. coli bund...

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Section: Discussionmentioning

confidence: 99%

The Vibrio cholerae Cpx Envelope Stress Response Senses and Mediates Adaptation to Low Iron

2014

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“…Studies of E. coli and other bacteria have shown that DsbD keeps DsbC and DsbG, two disulfide bond isomerases (2, 4, 32, 52) in a reduced state, thereby maintaining the capacity of these proteins to convert incorrect disulfide bonds to their proper forms. DsbD also promotes the maturation of cytochrome c through its interactions with DsbE (also known as CcmG) (3,14,56). DsbC (VC2418) and DsbE (VC2051) are 37.5% and 54.8% identical to their respective E. coli counterparts; no V. cholerae homologue of DsbG was identifiable using BLAST.…”

Section: B11mentioning

confidence: 99%

Genetic Analysis of Activation of the Vibrio cholerae Cpx Pathway

Slamti

Waldor

2009

J Bacteriol

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The Cpx two-component system is thought to mediate envelope stress responses in many gram-negative bacteria and has been implicated in the pathogenicity of several enteric pathogens. While cues that activate the Escherichia coli Cpx system have been identified, the nature of the molecular signals that stimulate this pathway is not well understood. Here, we investigated stimuli that trigger this system in Vibrio cholerae, a facultative pathogen that adapts to various niches during its life cycle. In contrast to E. coli, there was no basal activity of the V. cholerae Cpx pathway under standard laboratory conditions. Furthermore, several known stimuli of the E. coli pathway did not induce expression of this system in V. cholerae. There were no defects in intestinal growth in V. cholerae cpx mutants, arguing against the idea that this pathway promotes V. cholerae adaptation to conditions in the mammalian host. We discovered that chloride ions activate the V. cholerae Cpx pathway, raising the possibility that this signal transduction system provides a means for V. cholerae to sense and respond to alterations in salinity. We used a genetic approach to screen for mutants in which the Cpx pathway is activated. We found that mutations in genes whose products are required for periplasmic disulfide bond isomerization result in activation of the Cpx pathway, suggesting that periplasmic accumulation of proteins with aberrant disulfide bonds triggers the V. cholerae Cpx pathway.

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“…However, CcmG is not the terminal reductase in system I CCM; i.e., it occurs earlier in the transfer chain, accepting electrons from the transmembrane DsbD protein and passing them on to CcmH (39). Furthermore, the majority of extracytoplasmic TDORs in B. subtilis and E. coli do not function in CCM.…”

Section: Replacement Of the N-terminal Transmembrane Anchor Ofmentioning

confidence: 99%

The Active-Site Cysteinyls and Hydrophobic Cavity Residues of ResA Are Important for CytochromecMaturation inBacillus subtilis

et al. 2008

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ResA is an extracytoplasmic membrane-bound thiol-disulfide oxidoreductase required for cytochrome c maturation in Bacillus subtilis. Previous biochemical and structural studies have revealed that the active-site cysteinyls cycle between oxidized and reduced states with a low reduction potential and that, upon reduction, a hydrophobic cavity forms close to the active site. Here we report in vivo studies of ResA-deficient B. subtilis complemented with a series of ResA variants. Using a range of methods to analyze the cellular cytochrome c content, we demonstrated (i) that the N-terminal transmembrane segment of ResA serves principally to anchor the protein to the cytoplasmic membrane but also plays a role in mediating the activity of the protein; (ii) that the active-site cysteines are important for cytochrome c maturation activity; (iii) that Pro141, which forms part of the hydrophobic cavity and which adopts a cis conformation, plays an important role in protein stability; (iv) that Glu80, which lies at the base of the hydrophobic cavity, is important for cytochrome c maturation activity; and, finally, (v) that Pro141 and Glu80 ResA mutant variants promote selective maturation of low levels of one c-type cytochrome, subunit II of the cytochrome c oxidase caa 3 , indicating that this apocytochrome is distinct from the other three endogenous c-type cytochromes of B. subtilis.

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Structural Basis and Kinetics of DsbD-Dependent Cytochrome c Maturation

Cited by 76 publications

References 47 publications

The Vibrio cholerae Cpx Envelope Stress Response Senses and Mediates Adaptation to Low Iron

The Vibrio cholerae Cpx Envelope Stress Response Senses and Mediates Adaptation to Low Iron

Genetic Analysis of Activation of the Vibrio cholerae Cpx Pathway

The Active-Site Cysteinyls and Hydrophobic Cavity Residues of ResA Are Important for CytochromecMaturation inBacillus subtilis

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