title: Acidic pH and divalent cation sensing by PhoQ are dispensable for systemic salmonellae virulence.
abstract: Salmonella PhoQ is a histidine kinase with a periplasmic sensor domain (PD) that promotes virulence by detecting the macrophage phagosome. PhoQ activity is repressed by divalent cations and induced in environments of acidic pH, limited divalent cations, and cationic antimicrobial peptides (CAMP). Previously, it was unclear which signals are sensed by salmonellae to promote PhoQ-mediated virulence. We defined conformational changes produced in the PhoQ PD on exposure to acidic pH that indicate structural flexibility is induced in α-helices 4 and 5, suggesting this region contributes to pH sensing. Therefore, we engineered a disulfide bond between W104C and A128C in the PhoQ PD that restrains conformational flexibility in α-helices 4 and 5. PhoQ(W104C-A128C) is responsive to CAMP, but is inhibited for activation by acidic pH and divalent cation limitation. phoQ(W104C-A128C) Salmonella enterica Typhimurium is virulent in mice, indicating that acidic pH and divalent cation sensing by PhoQ are dispensable for virulence.
authors.affiliation: Department of Microbiology, University of Washington Medical School, Seattle, United States.
authors.forename: Kevin G
authors.initials: KG
authors.lastname: Hicks
authors.affiliation: Department of Biochemistry, University of Washington Medical School, Seattle, United States.
authors.forename: Scott P
authors.initials: SP
authors.lastname: Delbecq
authors.affiliation: Unidad de Biofisica, Centro Mixto Consejo Superior de Investigaciones Cientificas-Universidad del País Vasco/Euskal Herriko Unibertsitatea (CSIC,UPV/EHU), Leioa, Bizkaia, Spain.
authors.forename: Enea
authors.initials: E
authors.lastname: Sancho-Vaello
authors.affiliation: Department of Microbiology, University of Washington Medical School, Seattle, United States.
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Blanc
authors.affiliation: Department of Biochemistry, University of Washington Medical School, Seattle, United States.
authors.forename: Katja K
authors.initials: KK
authors.lastname: Dove
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, Madison, United States.
authors.forename: Lynne R
authors.initials: LR
authors.lastname: Prost
authors.affiliation: Department of Chemistry and Biochemistry, University of San Diego, San Diego, United States.
authors.forename: Margaret E
authors.initials: ME
authors.lastname: Daley
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Basque Country, Leioa, Spain.
authors.forename: Kornelius
authors.initials: K
authors.lastname: Zeth
authors.affiliation: Department of Biochemistry, University of Washington Medical School, Seattle, United States.
authors.forename: Rachel E
authors.initials: RE
authors.lastname: Klevit
authors.affiliation: Department of Microbiology, University of Washington Medical School, Seattle, United States.
authors.forename: Samuel I
authors.initials: SI
authors.lastname: Miller
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002413:Cations, Divalent / Q000378:metabolism*; D018360:Crystallography, X-Ray; D015964:Gene Expression Regulation, Bacterial; D006863:Hydrogen-Ion Concentration; D051379:Mice; D008958:Models, Molecular; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation / Q000187:drug effects; D012481:Salmonella Infections, Animal / Q000382:microbiology / Q000473:pathology; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000472:pathogenicity*; D014774:Virulence; D037521:Virulence Factors / Q000096:biosynthesis*
chemical_list: D001426:Bacterial Proteins; D002413:Cations, Divalent; D050505:Mutant Proteins; C079792:PhoQ protein, Bacteria; D037521:Virulence Factors
keywords: Salmonella; bacterial pathogenesis; biochemistry; infectious disease; innate immunity; intracellular virulence; microbiology; sensor kinase; signal transduction