FieF (YiiP) from Escherichia coli mediates decreased cellular accumulation of iron and relieves iron stress.
The Escherichia coli yiiP gene encodes an iron transporter, ferrous iron efflux (FieF), which belongs to the cation diffusion facilitator family (CDF). Transcription of fieF correlated with iron concentration; however, expression appeared to be independent of the ferrous iron uptake regulator Fur. Absence of FieF led to decreased growth of E. coli cells in complex growth medium but only if fur was additionally deleted. The presence of EDTA was partially able to relieve this growth deficiency. Expression of fieF in trans rendered the double deletion strain more tolerant to iron. Furthermore, E. coli cells exhibited reduced accumulation of (55)Fe when FieF was expressed in trans. FieF catalyzed active efflux of Zn(II) in antiport with protons energized by NADH via the transmembrane pH gradient in everted membrane vesicles. Using the iron-sensitive fluorescent indicator PhenGreen-SK encapsulated in proteoliposomes, transmembrane fluxes of iron cations were measured with purified and reconstituted FieF by fluorescence quenching. This suggests that FieF is an iron and zinc efflux system, which would be the first example of iron detoxification by efflux in any organism.
Grass
Gregor
G
Institut für Mikrobiologie, Martin-Luther-Universität Halle, Kurt-Mothes-Str. 3, Halle 06120, Germany. g.grass@mikrobiologie.uni-halle.de
Otto
Markus
M
Fricke
Beate
B
Haney
Christopher J
CJ
Rensing
Christopher
C
Nies
Dietrich H
DH
Munkelt
Doreen
D
D001426:Bacterial Proteins / Q000378:metabolism; D001693:Biological Transport, Active / Q000235:genetics / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000378:metabolism; D017353:Gene Deletion; D005816:Genetic Complementation Test; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport / Q000235:genetics; D007501:Iron / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D009930:Organic Chemicals; D012097:Repressor Proteins / Q000378:metabolism; D015032:Zinc / Q000378:metabolism
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D005456:Fluorescent Dyes; D026901:Membrane Transport Proteins; D009930:Organic Chemicals; C431805:Phen Green SK; D012097:Repressor Proteins; C486459:YiiP protein, E coli; C068477:ferric uptake regulating proteins, bacterial; D007501:Iron; D015032:Zinc