Multiple regulators of the Flavohaemoglobin (hmp) gene of Salmonella enterica serovar Typhimurium include RamA, a transcriptional regulator conferring the multidrug resistance phenotype.
Microbial flavohaemoglobins are proteins with homology to haemoglobins from higher organisms, but clearly linked to nitric oxide (NO) metabolism by bacteria and yeast. hmp mutant strains of several bacteria are hypersensitive to NO and related compounds and hmp genes are up-regulated by the presence of NO. The regulatory mechanisms involved in hmp induction by NO and the superoxide-generating agent, methyl viologen (paraquat; PQ), are complex, but progressively being resolved. Here we show for the first time that, in Salmonella enterica serovar Typhimurium, hmp transcription is increased on exposure to PQ and demonstrate that RamA, a homologue of MarA is responsible for most of the hmp paraquat regulation. In addition we demonstrate NO-dependent elevation of Salmonella hmp transcription and Hmp accumulation. In both Escherichia coli and Salmonella modest transcriptional repression of hmp is exerted by the iron responsive transcriptional repressor Fur. Finally, in contrast to previous reports, we show that in E. coli and Salmonella, hmp induction by both paraquat and sodium nitroprusside is further elevated in a fur mutant background, indicating that additional regulators are implicated in this control process.
Hernández-Urzúa
Elizabeth
E
Laboratorio de Microbiología y Genética Molecular, Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, PO Box 70-228, Coyoacán, Mexico City 04510, Mexico.
Zamorano-Sánchez
David S
DS
Ponce-Coria
José
J
Morett
Enrique
E
Grogan
Susan
S
Poole
Robert K
RK
Membrillo-Hernández
Jorge
J
D001426:Bacterial Proteins / Q000378:metabolism*; D004093:Dihydropteridine Reductase / Q000235:genetics / Q000502:physiology*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000502:physiology*; D005809:Genes, Regulator; D006420:Hemeproteins / Q000235:genetics / Q000502:physiology*; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics / Q000502:physiology*; D010641:Phenotype; D019779:Salmonella enterica / Q000235:genetics* / Q000502:physiology*; D015534:Trans-Activators / Q000235:genetics; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D006420:Hemeproteins; D015534:Trans-Activators; C453342:rma protein, Salmonella; D004093:Dihydropteridine Reductase; C076538:hmp protein, E coli; D009247:NADH, NADPH Oxidoreductases