title: VfrB Is a Key Activator of the Staphylococcus aureus SaeRS Two-Component System.
abstract: In previous studies, we identified the fatty acid kinase virulence factor regulator B (VfrB) as a potent regulator of α-hemolysin and other virulence factors inStaphylococcus aureusIn this study, we demonstrated that VfrB is a positive activator of the SaeRS two-component regulatory system. Analysis ofvfrB,saeR, andsaeSmutant 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 thevfrBmutant, compared to the wild-type strain. In addition,saePQRSexpression was decreased in thevfrBmutant 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,hlaexpression was decreased in thevfrBmutant 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 α-hemolysin production. Collectively, this study implicates VfrB as a novel accessory protein needed for the activation of SaeRS inS. aureusIMPORTANCEThe SaeRS two-component system is a key regulator of virulence determinant production inStaphylococcus aureusAlthough the regulon of this two-component 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 inS. aureusIn addition to describing a new regulatory aspect of SaeRS, this study establishes a link between fatty acid kinase activity and virulence factor regulation.
authors.affiliation: Department of Microbiology, Molecular Genetics, and Immunology, University of Kansas Medical Center, Kansas City, Kansas, USA.
authors.forename: Christina N
authors.initials: CN
authors.lastname: Krute
authors.affiliation: Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, Florida, USA.
authors.forename: Kelly C
authors.initials: KC
authors.lastname: Rice
authors.affiliation: Department of Microbiology, Molecular Genetics, and Immunology, University of Kansas Medical Center, Kansas City, Kansas, USA jbose@kumc.edu.
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Bose
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D017124:Conserved Sequence; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D013211:Staphylococcus aureus / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors
chemical_list: D001426:Bacterial Proteins; C433805:SaeR protein, Staphylococcus aureus; D014157:Transcription Factors; D011494:Protein Kinases; C527351:SaeS protein, Staphylococcus aureus
keywords: SaeRS; VfrB; fatty acid kinase; regulation; two-component system