title: The temperature-sensing protein TlpA is repressed by PhoP and dispensable for virulence of Salmonella enterica serovar Typhimurium in mice.
abstract: TlpA is a temperature-sensing, coiled-coil protein, encoded on the pSLT virulence plasmid of Salmonella enterica serovar Typhimurium. TlpA was previously presumed to play a role in the pathogenicity of Salmonella. Herein we show that TlpA is tightly regulated, differentially expressed in response to environmental and physiological signals, and can be secreted in vitro. Expression of tlpA was found to be repressed in modified minimal medium containing limiting concentrations of Mg2+ and in the stationary phase of growth, but induced in rich LB broth and in response to elevated temperatures. The response regulator PhoP was found to play a key role in the repression of tlpA in conjunction with two other regulators, RpoS and TlpA itself. In addition, we demonstrate that TlpA is dispensable for intracellular proliferation of S. Typhimurium within host cells and for virulence in mice. Based on presented homology of TlpA to the IncP plasmid encoded protein, KfrA, and to SMC family members, a potential function for TlpA is discussed. Cumulatively, our data do not support the previous hypothesis that TlpA plays a role in the pathogenicity of Salmonella per se, but may suggest an alternative function for TlpA unrelated to host infection.
authors.affiliation: Michael Smith Laboratories, University of British Columbia, Room 301, 2185 East Mall, Vancouver, BC V6T 1Z4, Canada.
authors.forename: Ohad
authors.initials: O
authors.lastname: Gal-Mor
authors.forename: Yanet
authors.initials: Y
authors.lastname: Valdez
authors.forename: B Brett
authors.initials: BB
authors.lastname: Finlay
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019677:Artificial Gene Fusion; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D003470:Culture Media / Q000737:chemistry; D005260:Female; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D012481:Salmonella Infections, Animal / Q000382:microbiology*; D012486:Salmonella typhimurium / Q000472:pathogenicity*; D017385:Sequence Homology; D012808:Sigma Factor / Q000502:physiology; D016019:Survival Analysis; D013696:Temperature; D014774:Virulence; D001616:beta-Galactosidase / Q000032:analysis / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; C061064:PhoP protein, Bacteria; C075138:TlpA protein, Salmonella; D001616:beta-Galactosidase