Thiol-Disulfide Exchange in Gram-Positive Firmicutes

Davey, Lauren; Halperin, Scott A.; Lee, Song F.

doi:10.1016/j.tim.2016.06.010

“…These pathways usually comprise a carrier enzyme, that delivers the disulfide bond to target proteins, and a donor enzyme, that generates the disulfide bond de novo . d i s ulfide b ond formation protein A (DsbA) or DsbA-like oxidoreductases are the primary disulfide-bond carrier in prokaryotes, located in the periplasmic space of gram-negative bacteria 3 (Figure 1A) or at the cell wall of gram-positive bacteria 4 . DsbA is one of the most oxidizing enzymes 5 with a broad substrate spectrum: ∼ 300 periplasmic proteins in Escherichia coli are predicted to be oxidized by DsbA 6 .…”

Section: Thiol Oxidoreductases In the Disulfide-relay Pathwaysmentioning

confidence: 99%

Intramembrane Thiol Oxidoreductases: Evolutionary Convergence and Structural Controversy

Li

¹

,

Shen

²

,

Li

³

2017

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During oxidative protein folding, the disulfide-bond formation is catalyzed by thioloxidoreductases. Through dedicated relay pathways, the disulfide is generated in donor enzymes, passed to carrier enzymes, and subsequently delivered to target proteins. The eukaryotic disulfide donors are flavoenzymes, Ero1 in endoplasmic reticulum and Erv1 in mitochondria. In prokaryotes, disulfide generation is coupled to quinone reduction, catalyzed by intramembrane donor enzymes, DsbB and VKOR. To catalyze de novo disulfide formation, these different disulfide donors show striking structural convergences in several levels. They share a four-helix-bundle core structure at their active site, which contains a CXXC motif at a helical end. They have also evolved a flexible loop with shuttle cysteines to transfer electrons to the active site and relay the disulfide bond to the carrier enzymes. Studies of the prokaryotic VKOR, however, have stirred debate of whether the human homolog adopts the same topology with four transmembrane helices and uses the same electron-transfer mechanism. The controversies have recently been resolved by investigating the human VKOR structure and catalytic process in living cells with a mass spectrometry based approach. Structural convergence is found between human VKOR and the disulfide donors to underlie the cofactor reduction, disulfide generation, and electron transfer.

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“…In the B. subtilis extracytoplasmic space, disulfide bond formation is catalyzed by one of two thiol-disulfide oxidoreductases (TDORs) named BdbA and BdbD (20)(21)(22). We predicted that if BslA was actively oligomerized, then disruption of either bdbA or bdbD (or both in the case of functional redundancy) would produce a structured, but wetting, biofilm similar to the phenotype displayed by the monomeric BslA variants.…”

Section: Formation Of the Hydrophobic Layer Depends On Thiol-disulfidementioning

confidence: 99%

Bifunctionality of a biofilm matrix protein controlled by redox state

Arnaouteli

¹

,

Ferreira

²

,

Schor

³

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Biofilms are communities of microbial cells that are encapsulated within a self-produced polymeric matrix. The matrix is critical to the success of biofilms in diverse habitats; however, many details of the composition, structure, and function remain enigmatic. Biofilms formed by the Gram-positive bacteriumBacillus subtilisdepend on the production of the secreted film-forming protein BslA. Here, we show that a gradient of electron acceptor availability through the depth of the biofilm gives rise to two distinct functional roles for BslA and that these roles can be genetically separated through targeted amino acid substitutions. We establish that monomeric BslA is necessary and sufficient to give rise to complex biofilm architecture, whereas dimerization of BslA is required to render the community hydrophobic. Dimerization of BslA, mediated by disulfide bond formation, depends on two conserved cysteine residues located in the C-terminal region. Our findings demonstrate that bacteria have evolved multiple uses for limited elements in the matrix, allowing for alternative responses in a complex, changing environment.

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“…In the B. subtilis extracytoplasmic space disulfide bond formation is catalysed by one of two thioldisulfide oxidoreductases (TDORs) named BdbA and BdbD (20)(21)(22). We predicted that if BslA was actively oligomerised then disruption of either bdbA or bdbD (or both in the case of functional redundancy) would produce a structured but wetting biofilm similar to the phenotype displayed by the monomeric BslA variants.…”

Section: Formation Of the Hydrophobic Layer Depends On Thiol-disulfidmentioning

confidence: 99%

Bifunctionality of a biofilm matrix protein controlled by redox state

Arnaouteli

¹

,

Ferreira

²

,

Schor

³

et al. 2017

Preprint

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Biofilms are communities of microbial cells that are encapsulated within a self-produced polymeric matrix. The matrix is critical to the success of biofilms in diverse habitats, but despite this many details of the composition, structure, and function remain enigmatic. Biofilms formed by the Gram-positive bacterium Bacillus subtilis depend on the production of the secreted film-forming protein BslA. Here we show that a gradient of electron acceptor availability through the depth of the biofilm gives rise to two distinct functional roles for BslA and that these can be genetically separated through targeted amino acid substitutions. We establish that monomeric BslA is necessary and sufficient to give rise to complex biofilm architecture, while dimerization of BslA is required to render the community hydrophobic. Dimerization of BslA, mediated by disulfide bond formation, depends on two conserved cysteine residues located in the C-terminal region. Our findings demonstrate that bacteria have evolved multiple uses for limited elements in the matrix, allowing for alternative responses in a complex, changing environment.SignificanceThe biofilm matrix is a critical target in the hunt for novel strategies to destabilise or stabilise biofilms. Knowledge of the processes controlling matrix assembly is therefore an essential prerequisite to exploitation. Here we highlight that the complexity of the biofilm matrix is even higher than anticipated with one matrix component making two independent functional contributions to the community. The influence the protein exerts is dependent on the local environmental properties, providing another dimension to consider during analysis. These findings add to the evidence that bacteria can evolve multifunctional uses for the extracellular matrix components.

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Thiol-Disulfide Exchange in Gram-Positive Firmicutes

Cited by 34 publications

References 93 publications

Intramembrane Thiol Oxidoreductases: Evolutionary Convergence and Structural Controversy

Intramembrane Thiol Oxidoreductases: Evolutionary Convergence and Structural Controversy

Bifunctionality of a biofilm matrix protein controlled by redox state

Bifunctionality of a biofilm matrix protein controlled by redox state

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