CHARACTERIZATION OF THE FERROUS IRON UPTAKE SYSTEM OF ESCHERICHIA-COLI

Escherichia coli has an iron(II) transport system (feo) which may make an important contribution to the iron supply of the cell under anaero bic conditions. Cloning and sequencing of the iron(II) transport genes revealed an open reading frame (feoA) possibly coding for a small pro tein with 75 amino acids and a membrane protein with 773 amino acids ( feoB). The upstream region of feoAB contained a binding site for the r egulatory protein Fur, which acts with iron(II) as a corepressor in al l known iron transport systems of E. coli. In addition, a Fnr binding site was identified in the promoter region. The FeoB protein had an ap parent molecular mass of 70 kDa in sodium dodecyl sulfate-polyacrylami de gel electrophoresis and was localized in the cytoplasmic membrane. The sequence revealed regions of homology to ATPases, which indicates that ferrous iron uptake may be ATP driven. FeoA or FeoB mutants could be complemented by clones with the feoA or feoB gene, respectively.