Iron-responsive regulation of the Helicobacter pylori iron-cofactored superoxide dismutase SodB is mediated by Fur.
Maintaining iron homeostasis is a necessity for all living organisms, as free iron augments the generation of reactive oxygen species like superoxide anions, at the risk of subsequent lethal cellular damage. The iron-responsive regulator Fur controls iron metabolism in many bacteria, including the important human pathogen Helicobacter pylori, and thus is directly or indirectly involved in regulation of oxidative stress defense. Here we demonstrate that Fur is a direct regulator of the H. pylori iron-cofactored superoxide dismutase SodB, which is essential for the defense against toxic superoxide radicals. Transcription of the sodB gene was iron induced in H. pylori wild-type strain 26695, resulting in expression of the SodB protein in iron-replete conditions but an absence of expression in iron-restricted conditions. Mutation of the fur gene resulted in constitutive, iron-independent expression of SodB. Recombinant H. pylori Fur protein bound with low affinity to the sodB promoter region, but addition of the iron substitute Mn2+ abolished binding. The operator sequence of the iron-free form of Fur, as identified by DNase I footprinting, was located directly upstream of the sodB gene at positions -5 to -47 from the transcription start site. The direct role of Fur in regulation of the H. pylori sodB gene contrasts with the small-RNA-mediated sodB regulation observed in Escherichia coli. In conclusion, H. pylori Fur is a versatile regulator involved in many pathways essential for gastric colonization, including superoxide stress defense.
Ernst
Florian D
FD
Department of Gastroenterology and Hepatology, Erasmus MC-University Medical Center, Dijkzigt L-4, Dr. Molewaterplein 40, 3015 GD Rotterdam, The Netherlands.
Homuth
Georg
G
Stoof
Jeroen
J
Mäder
Ulrike
U
Waidner
Barbara
B
Kuipers
Ernst J
EJ
Kist
Manfred
M
Kusters
Johannes G
JG
Bereswill
Stefan
S
van Vliet
Arnoud H M
AH
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D018983:DNA Footprinting; D015964:Gene Expression Regulation, Bacterial; D016480:Helicobacter pylori / Q000235:genetics* / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000502:physiology; D012097:Repressor Proteins / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000235:genetics* / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D012097:Repressor Proteins; C068477:ferric uptake regulating proteins, bacterial; D013481:Superoxides; D007501:Iron; C087504:SodB protein, Bacteria; D013482:Superoxide Dismutase