title: Control of the Salmonella ugd gene by three two-component regulatory systems.
abstract: The Salmonella ugd gene is required for the incorporation of 4-aminoarabinose in the lipopolysaccharide and resistance to the antibiotic polymyxin B. Transcription of the ugd gene is induced by Fe3+ via the PmrA-PmrB two-component system and by low Mg2+ in a process that requires the PhoP-PhoQ two-component system, the PhoP-activated PmrD protein and the PmrA-PmrB system. Here, we establish that mutation of the tolB gene promotes ugd transcription independently of both the PhoP-PhoQ and PmrA-PmrB systems. This activation is mediated by the RcsC-YojN-RcsB phosphorelay and the RcsA protein, suggesting a role for ugd in capsule synthesis. Binding sites for the RcsB, PmrA and PhoP proteins were identified in the ugd promoter. Although the PmrA-PmrB and RcsC-YojN-RcsB systems promoted ugd transcription independently of the PhoP-PhoQ system under different environmental conditions, ugd expression inside macrophages was strictly dependent on PhoP-PhoQ, suggesting that low Mg2+ is a cue for the intracellular environment.
authors.affiliation: Department of Molecular Microbiology, Howard Hughes Medical Institute, Washington U niversity School of Medicine, 660 S. Euclid, St. Louis, MO 63110, USA.
authors.forename: Chakib
authors.initials: C
authors.lastname: Mouslim
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Groisman
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D004742:Enhancer Elements, Genetic; D015964:Gene Expression Regulation, Bacterial; D008264:Macrophages / Q000382:microbiology; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D012475:Salmonella / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D015398:Signal Transduction; D014158:Transcription, Genetic; D014533:Uridine Diphosphate Glucose Dehydrogenase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D014533:Uridine Diphosphate Glucose Dehydrogenase