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The Fur repressor controls transcription of iron‐activated and ‐repressed genes in Helicobacter pylori
Author(s) -
Delany Isabel,
Spohn Gunther,
Rappuoli Rino,
Scarlato Vincenzo
Publication year - 2001
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2001.02696.x
Subject(s) - derepression , repressor , biology , promoter , psychological repression , microbiology and biotechnology , gene , transcription (linguistics) , mutant , regulation of gene expression , transcription factor , gene expression , biochemistry , linguistics , philosophy
The ferric uptake regulator (Fur) protein is known to act as a Fe 2+ ‐dependent transcriptional repressor of bacterial promoters. Here, we show that, in Helicobacter pylori , Fur can mediate the regulation of iron‐activated genes in contrast to classical Fur regulation, in which iron acts as a co‐repressor. Inactivation of the fur gene in the chromosome of H. pylori resulted in the derepression of a 19 kDa protein that was identified by N‐terminal sequencing as the non‐haem‐containing ferritin (Pfr). Growth of the wild‐type H. pylori strain on media treated with increasing concentrations of FeSO 4 resulted in induction of transcription from the P pfr promoter and, conversely, depletion of iron resulted in repression of P pfr , indicating that this promoter is iron activated. In the fur mutant, the P pfr promoter is constitutively highly expressed and no longer responds to iron, indicating that the Fur protein mediates this type of iron regulation. Footprinting analysis revealed that Fur binds to the P pfr promoter region and that Fe 2+ decreases the efficiency of binding. In contrast, Fe 2+ increased the affinity of Fur for a classical Fur‐regulated promoter, the iron‐repressed frpB gene promoter. To our knowledge, this is the first evidence of direct interaction between the Fur protein and the promoter of an iron‐activated (‐derepressed) gene. Our results support a model in which the iron status of the Fur protein differentially alters its affinity for operators in either iron‐repressed or iron‐activated genes.