Functional Analysis of Paralogous Thiol-disulfide Oxidoreductases in Streptococcus gordonii

Davey, Lauren; Ng, Crystal K.W.; Halperin, Scott A.; Lee, Song F.

doi:10.1074/jbc.m113.464578

Cited by 21 publications

(48 citation statements)

References 64 publications

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“…Further analysis is needed to elucidate the role of SaDsbA in vivo. Finally, a single DsbA-like factor has also been identified in S. gordonii (67). Similar to B. subtilis and S. aureus, this putative oxidoreductase has been implicated in competence development.…”

Section: Gram-positive Disulfide-bond-forming Pathwaysmentioning

confidence: 91%

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Disulfide-Bond-Forming Pathways in Gram-Positive Bacteria

Reardon-Robinson

Ton‐That

2016

J Bacteriol

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Disulfide bonds are important for the stability and function of many secreted proteins. In Gram-negative bacteria, these linkages are catalyzed by thiol-disulfide oxidoreductases (Dsb) in the periplasm. Protein oxidation has been well studied in these organisms, but it has not fully been explored in Gram-positive bacteria, which lack traditional periplasmic compartments. Recent bioinformatics analyses have suggested that the high-GC-content bacteria (i.e., actinobacteria) rely on disulfide-bond-forming pathways. In support of this, Dsb-like proteins have been identified in Mycobacterium tuberculosis, but their functions are not known. Actinomyces oris and Corynebacterium diphtheriae have recently emerged as models to study disulfide bond formation in actinobacteria. In both organisms, disulfide bonds are catalyzed by the membrane-bound oxidoreductase MdbA. Remarkably, unlike known Dsb proteins, MdbA is important for pathogenesis and growth, which makes it a potential target for new antibacterial drugs. This review will discuss disulfide-bond-forming pathways in bacteria, with a special focus on Gram-positive bacteria.

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Section: Gram-positive Disulfide-bond-forming Pathwaysmentioning

confidence: 91%

“…DsbA-like genes have also been identified in Staphylococcus aureus and Streptococcus gordonii (66,67). S. aureus DsbA (SaDsbA) is a membrane-bound lipoprotein that was shown in vitro to have thiol-disulfide oxidoreductase activity (68).…”

Section: Gram-positive Disulfide-bond-forming Pathwaysmentioning

confidence: 99%

Disulfide-Bond-Forming Pathways in Gram-Positive Bacteria

Reardon-Robinson

Ton‐That

2016

J Bacteriol

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“…Previously, we found that ⌬sdbA mutants were defective in bacteriocin activity (26). To investigate how SdbA affects bacteriocin production, we started by constructing a catalytically inactive SdbA active site mutant, to determine whether bacteriocin production requires the oxidoreductase activity of SdbA.…”

Section: Resultsmentioning

confidence: 99%

“…S. gordonii SecCR1 is a derivative of S. gordonii DL-1 Challis that secretes a single-chain variablefragment antibody (scFv) against complement receptor 1 (CR1), which is a protein that requires disulfide bonds for stability (30). This strain was used in our previous studies of disulfide bond formation in S. gordonii (26), and the S. gordonii SecCR1 ⌬sdbA mutant has the same phenotype as the ⌬sdbA mutant of S. gordonii DL-1 Challis (see Fig. S1 in the supplemental material).…”

Section: Methodsmentioning

confidence: 99%

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Mutation of the Thiol-Disulfide Oxidoreductase SdbA Activates the CiaRH Two-Component System, Leading to Bacteriocin Expression Shutdown in Streptococcus gordonii

2016

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Streptococcus gordonii is a commensal inhabitant of the human oral cavity. To maintain its presence as a major component of oral biofilms, S. gordonii secretes inhibitory molecules such as hydrogen peroxide and bacteriocins to inhibit competitors. S. gordonii produces two nonmodified bacteriocins (i.e., Sth 1 and Sth 2 ) that are regulated by the Com two-component regulatory system, which also regulates genetic competence. Previously we found that the thiol-disulfide oxidoreductase SdbA was required for bacteriocin activity; however, the role of SdbA in Com signaling was not clear. Here we demonstrate that ⌬sdbA mutants lacked bacteriocin activity because the bacteriocin gene sthA was strongly repressed and the peptides were not secreted. Addition of synthetic competence-stimulating peptide to the medium reversed the phenotype, indicating that the Com pathway was functional but was not activated in the ⌬sdbA mutant. Repression of bacteriocin production was mediated by the CiaRH two-component system, which was strongly upregulated in the ⌬sdbA mutant, and inactivation of CiaRH restored bacteriocin production. The CiaRH-induced protease DegP was also upregulated in the ⌬sdbA mutant, although it was not required for inhibition of bacteriocin production. This establishes CiaRH as a regulator of Sth bacteriocin activity and links the CiaRH and Com systems in S. gordonii. It also suggests that either SdbA or one of its substrates is an important factor in regulating activation of the CiaRH system. IMPORTANCEStreptococcus gordonii is a noncariogenic colonizer of the human oral cavity. To be competitive in the oral biofilm, S. gordonii secretes antimicrobial peptides called bacteriocins, which inhibit closely related species. Our previous data showed that mutation of the disulfide oxidoreductase SdbA abolished bacteriocin production. In this study, we show that mutation of SdbA generates a signal that upregulates the CiaRH two-component system, which in turn downregulates a second two-component system, Com, which regulates bacteriocin expression. Our data show that these systems are also linked in S. gordonii, and the data reveal that the cell's ability to form disulfide bonds is sensed by the CiaRH system. O ral biofilms are highly competitive, constantly fluctuating environments. The bacteria that colonize this niche contend with a high density of competing bacteria of an estimated 2,000 different taxa and dramatic environmental changes that are dependent on host behavior (1, 2). Streptococcus gordonii is a pioneer colonizer of this environment, where it initiates biofilm formation by binding directly to the acquired salivary pellicle on the tooth surface (2, 3). Once established, S. gordonii persists within the host as part of the oral microbiota. The presence of S. gordonii is associated with oral health (4, 5), and it has been shown to inhibit biofilm formation by cariogenic species (6, 7).S. gordonii uses several strategies to gain advantage over its competitors and to colonize the oral cavity successfully...

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