SarT, a Repressor of α-Hemolysin in
            <i>Staphylococcus aureus</i>

Schmidt, Katherine A.; Manna, A. La; Gill, Steven R.; Cheung, Ambrose L.

doi:10.1128/iai.69.8.4749-4758.2001

Cited by 108 publications

(136 citation statements)

References 43 publications

(48 reference statements)

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“…Similar to saeRS mutants (28), vfrB mutants show a marked reduction in Hla-dependent hemolytic activity when grown on rabbit blood agar, demonstrating decreased ability to produce Hla, and have enhanced production of V8 protease (26). Hla is under the control of multiple transcriptional and posttranscriptional factors (29)(30)(31)(32)(33)(34). Since Sae is known to be a major contributor to hla expression, we sought to determine whether changes in Hla activity in response to VfrB are in the same pathway as SaeRS or in independent pathways.…”

Section: Resultsmentioning

confidence: 99%

“…An additional explanation for this discrepancy in the necessity of VfrB for class I and class II promoters is that class I promoters have two SaeR-binding sites, whereas class II promoters have a single SaeR-binding site (14); therefore, higher levels of phosphorylated SaeR are required to activate class I promoters. Finally, in addition to the regulation of hla by SaeRS, several other master regulatory factors (e.g., Agr, RNAIII, Rot, SarA, and SarT) influence transcription of the hemolysin (29)(30)(31)(32)(33)(34), adding additional levels of regulation that affect expression. Thus, it is plausible that the complex regulatory mechanisms that control hla expression also contribute to VfrB having less effect on this class II gene than on coa.…”

Section: Discussionmentioning

confidence: 99%

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VfrB Is a Key Activator of the Staphylococcus aureus SaeRS Two-Component System

2017

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In previous studies, we identified the fatty acid kinase virulence factor regulator B (VfrB) as a potent regulator of ␣-hemolysin and other virulence factors in Staphylococcus aureus. In this study, we demonstrated that VfrB is a positive activator of the SaeRS two-component regulatory system. Analysis of vfrB, saeR, and saeS mutant strains revealed that VfrB functions in the same pathway as SaeRS. At the transcriptional level, the promoter activities of SaeRS class I (coa) and class II (hla) target genes were downregulated during the exponential growth phase in the vfrB mutant, compared to the wild-type strain. In addition, saePQRS expression was decreased in the vfrB mutant strain, demonstrating a need for this protein in the autoregulation of SaeRS. The requirement for VfrB-mediated activation was circumvented when SaeS was constitutively active due to an SaeS (L18P) substitution. Furthermore, activation of SaeS via human neutrophil peptide 1 (HNP-1) overcame the dependence on VfrB for transcription from class I Sae promoters. Consistent with the role of VfrB in fatty acid metabolism, hla expression was decreased in the vfrB mutant with the addition of exogenous myristic acid. Lastly, we determined that aspartic acid residues D38 and D40, which are predicted to be key to VfrB enzymatic activity, were required for VfrB-mediated ␣-hemolysin production. Collectively, this study implicates VfrB as a novel accessory protein needed for the activation of SaeRS in S. aureus.IMPORTANCE The SaeRS two-component system is a key regulator of virulence determinant production in Staphylococcus aureus. Although the regulon of this twocomponent system is well characterized, the activation mechanisms, including the specific signaling molecules, remain elusive. Elucidating the complex regulatory circuit of SaeRS regulation is important for understanding how the system contributes to disease causation by this pathogen. To this end, we have identified the fatty acid kinase VfrB as a positive regulatory modulator of SaeRS-mediated transcription of virulence factors in S. aureus. In addition to describing a new regulatory aspect of SaeRS, this study establishes a link between fatty acid kinase activity and virulence factor regulation.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

VfrB Is a Key Activator of the Staphylococcus aureus SaeRS Two-Component System

2017

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“…The differences among them are also obvious enough for additional classification into three subfamilies. In the first subfamily, five helices and three short beta-strands are needed to build up a global structural domain for SarR, SarA, and possibly SarT, a repressor of ␣-hemolysin expression (34). Two identical domains form the functional homodimer.…”

Section: Discussionmentioning

confidence: 99%

Crystal Structure of the SarS Protein from Staphylococcus aureus

Manna

Dai

et al. 2003

J Bacteriol

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The expression of virulence determinants in Staphylococcus aureus is controlled by global regulatory loci (e.g., sarA and agr). One of these determinants, protein A (spa), is activated by sarS, which encodes a 250-residue DNA-binding protein. Genetic analysis indicated that the agr locus likely mediates spa repression by suppressing the transcription of sarS. Contrary to SarA and SarR, which require homodimer formation for proper function, SarS is unusual within the SarA protein family in that it contains two homologous halves, with each half sharing sequence similarity to SarA and SarR. Here we report the 2.2 Å resolution X-ray crystal structure of the SarS protein. SarS has folds similar to those of SarR and, quite plausibly, the native SarA structure. Two typical winged-helix DNA-binding domains are connected by a well-ordered loop. The interactions between the two domains are extensive and conserved. The putative DNA-binding surface is highly positively charged. In contrast, negatively charged patches are located opposite to the DNA-binding surface. Furthermore, sequence alignment and structural comparison revealed that MarR has folds similar to those of SarR and SarS. Members of the MarR protein family have previously been implicated in the negative regulation of an efflux pump involved in multiple antibiotic resistance in many gram-negative species. We propose that MarR also belongs to the winged-helix protein family and has a similar mode of DNA binding as SarR and SarS and possibly the entire SarA protein family member. Based on the structural differences of SarR, SarS, and MarR, we further classified these winged-helix proteins to three subfamilies, SarA, SarS, and MarR. Finally, a possible transcription regulation mechanism is proposed.

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“…A search of the recently released S. aureus genomes revealed at least 10 additional SarA homologs, six of which have been partially characterized. These members include SarR, SarS, SarT, SarU, SarV, and MgrA (also called Rat) (12)(13)(14)(15)(16). Members of the SarA protein family also share sequence homology with the MarR protein or homologs in Gram-negative bacteria (13).…”

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confidence: 99%

Structural and function analyses of the global regulatory protein SarA from Staphylococcus aureus

Liu

Manna

Pan

et al. 2006

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

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The sarA locus in Staphylococcus aureus controls the expression of many virulence genes. The sarA regulatory molecule, SarA, is a 14.7-kDa protein (124 residues) that binds to the promoter region of target genes. Here we report the 2.6 Å-resolution x-ray crystal structure of the dimeric winged helix SarA protein, which differs from the published SarA structure dramatically. In the crystal packing, multiple dimers of SarA form a scaffold, possibly via divalent cations. Mutations of individual residues within the DNAbinding helix-turn-helix and the winged region as well as within the metal-binding pocket implicate basic residues R84 and R90 within the winged region to be critical in DNA binding, whereas acidic residues D88 and E89 (wing), D8 and E11 (metal-binding pocket), and cysteine 9 are essential for SarA function. These data suggest that the winged region of the winged helix protein participates in DNA binding and activation, whereas the putative divalent cation binding pocket is only involved in gene function.

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SarT, a Repressor of α-Hemolysin in Staphylococcus aureus

Cited by 108 publications

References 43 publications

VfrB Is a Key Activator of the Staphylococcus aureus SaeRS Two-Component System

VfrB Is a Key Activator of the Staphylococcus aureus SaeRS Two-Component System

Crystal Structure of the SarS Protein from Staphylococcus aureus

Structural and function analyses of the global regulatory protein SarA from Staphylococcus aureus

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