title: A new ferrous iron-uptake transporter, EfeU (YcdN), from Escherichia coli.
abstract: 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.
authors.affiliation: Institute for Microbiology, Martin-Luther-University, Halle, Germany.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Grosse
authors.forename: Judith
authors.initials: J
authors.lastname: Scherer
authors.forename: Doreen
authors.initials: D
authors.lastname: Koch
authors.forename: Markus
authors.initials: M
authors.lastname: Otto
authors.forename: Nadine
authors.initials: N
authors.lastname: Taudte
authors.forename: Gregor
authors.initials: G
authors.lastname: Grass
mesh_terms: D000595:Amino Acid Sequence; D001692:Biological Transport; D027682:Cation Transport Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D007501:Iron / Q000378:metabolism* / Q000493:pharmacokinetics; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D008969:Molecular Sequence Data; D009876:Operon / Q000235:genetics; D011510:Proteolipids / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D027682:Cation Transport Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D011510:Proteolipids; C516304:efeU' protein, E coli; C020485:proteoliposomes; D007501:Iron