title: MglA/SspA complex interactions are modulated by inorganic polyphosphate.
abstract: The transcription factors MglA and SspA of Francisella tularensis form a heterodimer complex and interact with the RNA polymerase to regulate the expression of the Francisella pathogenicity island (FPI) genes. These genes are essential for this pathogen's virulence and survival within host cells. Our goal was to determine if an intracellular metabolite modulate these protein/protein interactions. In this study, we identified inorganic polyphosphate (polyP) as a signal molecule that promotes the interaction of MglA and SspA from F. tularensis SCHU S4. Analysis of the Mgla/SspA interaction was carried out using a two-hybrid system. The Escherichia coli reporter strain contained a deletion on the ppK-ppX operon, inhibiting polyP synthesis. The interaction between MglA and SspA was significantly impaired, as was the interaction between the MglA/SspA complex and the regulatory protein, FevR, indicating the stabilizing effect of polyP. In F. tularensis, chromatin immune precipitation studies revealed that in the absence of polyP, binding of the MglA/SspA complex to the promoter region of the pdpD, iglA, fevR and ppK genes is decreased. Isothermal titration calorimetry (ITC) indicated that polyP binds directly to the MglA/SspA complex with high affinity (KD = 0.3 µM). These observations directly correlated with results obtained from calorimetric scans (DSC), where a strong shift in the mid-transition temperature (Tm) of the MglA/SspA complex was observed in the presence of polyP.
authors.affiliation: Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Algevis P
authors.initials: AP
authors.lastname: Wrench
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Gardner
authors.forename: Sara D
authors.initials: SD
authors.lastname: Siegel
authors.forename: Fernando A
authors.initials: FA
authors.lastname: Pagliai
authors.forename: Mahsa
authors.initials: M
authors.lastname: Malekiha
authors.forename: Claudio F
authors.initials: CF
authors.lastname: Gonzalez
authors.forename: Graciela L
authors.initials: GL
authors.lastname: Lorca
mesh_terms: D017766:Acid Anhydride Hydrolases / Q000235:genetics / Q000378:metabolism; D018829:Adhesins, Bacterial / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002151:Calorimetry / Q000379:methods; D047369:Chromatin Immunoprecipitation; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005604:Francisella tularensis / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D009154:Mutation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism; D011122:Polyphosphates / Q000378:metabolism* / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D014774:Virulence / Q000235:genetics
chemical_list: D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D011122:Polyphosphates; C082314:SspA protein, bacteria; D014157:Transcription Factors; D017853:Phosphotransferases (Alcohol Group Acceptor); C475691:polyphosphate kinase, E coli; D017766:Acid Anhydride Hydrolases; C513394:Ppx protein, Escherichia coli