Journal of Bacteriology, November 2000, p. 5948-5953, Vol. 182, No. 21
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Department of Microbiology and Hygiene, Institute of Medical Microbiology and Hygiene,1 Institute of Microbiology,3 and Institute of Organic Chemistry and Biochemistry,4 University of Freiburg, D-79104 Freiburg, Germany, and Faculty of Medicine, Department of Medical Microbiology, Vrije Universiteit, 1081 BT Amsterdam, The Netherlands2
Received 12 April 2000/Accepted 1 August 2000
Homologs of the ferric uptake regulator Fur and the iron storage protein ferritin play a central role in maintaining iron homeostasis in bacteria. The gastric pathogen Helicobacter pylori contains an iron-induced prokaryotic ferritin (Pfr) which has been shown to be involved in protection against metal toxicity and a Fur homolog which has not been functionally characterized in H. pylori. Analysis of an isogenic fur-negative mutant revealed that H. pylori Fur is required for metal-dependent regulation of ferritin. Iron starvation, as well as medium supplementation with nickel, zinc, copper, and manganese at nontoxic concentrations, repressed synthesis of ferritin in the wild-type strain but not in the H. pylori fur mutant. Fur-mediated regulation of ferritin synthesis occurs at the mRNA level. With respect to the regulation of ferritin expression, Fur behaves like a global metal-dependent repressor which is activated under iron-restricted conditions but also responds to different metals. Downregulation of ferritin expression by Fur might secure the availability of free iron in the cytoplasm, especially if iron is scarce or titrated out by other metals.
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