Acidic pH and divalent cation sensing by PhoQ are dispensable for systemic salmonellae virulence
Kevin G Hicks,
Scott P Delbecq,
Enea Sancho-Vaello,
Marie-Pierre Blanc,
Katja K Dove,
Lynne R Prost,
Margaret E Daley,
Kornelius Zeth,
Rachel E Klevit,
Samuel I Miller
Affiliations
Kevin G Hicks
Department of Microbiology, University of Washington Medical School, Seattle, United States
Scott P Delbecq
Department of Biochemistry, University of Washington Medical School, Seattle, United States
Enea Sancho-Vaello
Unidad de Biofisica, Centro Mixto Consejo Superior de Investigaciones Cientificas-Universidad del País Vasco/Euskal Herriko Unibertsitatea (CSIC,UPV/EHU), Leioa, Bizkaia, Spain
Marie-Pierre Blanc
Department of Microbiology, University of Washington Medical School, Seattle, United States
Katja K Dove
Department of Biochemistry, University of Washington Medical School, Seattle, United States
Lynne R Prost
Department of Biochemistry, University of Wisconsin–Madison, Madison, United States
Margaret E Daley
Department of Chemistry and Biochemistry, University of San Diego, San Diego, United States
Kornelius Zeth
Department of Biochemistry and Molecular Biology, University of Basque Country, Leioa, Spain; IKERBASQUE, Basque Research Organisation for Science, Bilbao, Spain
Rachel E Klevit
Department of Biochemistry, University of Washington Medical School, Seattle, United States
Samuel I Miller
Department of Microbiology, University of Washington Medical School, Seattle, United States; Department of Genome Sciences, University of Washington Medical School, Seattle, United States; Department of Medicine, University of Washington Medical School, Seattle, United States
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. PhoQW104C-A128C is responsive to CAMP, but is inhibited for activation by acidic pH and divalent cation limitation. phoQW104C-A128C Salmonella enterica Typhimurium is virulent in mice, indicating that acidic pH and divalent cation sensing by PhoQ are dispensable for virulence.
