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A new ferrous iron‐uptake transporter, EfeU (YcdN), from Escherichia coli
Author(s) -
Große Cornelia,
Scherer Judith,
Koch Doreen,
Otto Markus,
Taudte Nadine,
Grass Gregor
Publication year - 2006
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 - 10.1111/j.1365-2958.2006.05326.x
Subject(s) - biology , escherichia coli , operon , permease , transmembrane domain , biochemistry , membrane transport protein , mutant , ferrous , transmembrane protein , repressor , ferrichrome , gene , microbiology and biotechnology , transporter , gene expression , bacterial outer membrane , chemistry , receptor , organic chemistry
Summary Escherichia coli possesses multiple routes for iron uptake. Here we present EfeU (YcdN), a novel iron acquisition system of E. coli strain Nissle 1917. Laboratory strains of E. coli such as K12 lack a functional ( efeU ) ycdN gene caused by a frameshift mutation. EfeU, a member of the oxidase‐dependent iron transporters (OFeT), is a homologue of the iron permease Ftr1p from yeast. The ycdN gene is part of the ycdNOB tricistronic operon which is expressed in response to iron deprivation in a Fur‐dependent manner. Expression of efeU resulted in improved growth of an E. coli mutant lacking all known iron‐uptake systems and mediated increased iron uptake into cells. Furthermore, the presence of other divalent metal cations did not impair growth of strains expressing efeU . The EfeU protein functioned as ferrous iron permease in proteoliposomes in vitro. Topology analysis indicated that EfeU is an integral cytoplasmic membrane protein exhibiting seven transmembrane helices. Two REXXE motifs within transmembrane helices of OFeT family members are implicated in iron translocation. Site‐directed mutagenesis of each REGLE motif of EfeU diminished iron uptake in vivo and growth yield. In vitro the EfeU variant protein with an altered first REGLE motif was impaired in iron permeation, whereas activity of the EfeU variant with a mutation in the second motif was similar to the wild‐type protein.