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J Bacteriol. 1989 May; 171(5): 2626–2633.
PMCID: PMC209944

Nucleotide sequences of the fecBCDE genes and locations of the proteins suggest a periplasmic-binding-protein-dependent transport mechanism for iron(III) dicitrate in Escherichia coli.


The fec region of the Escherichia coli chromosome determines a citrate-dependent iron(III) transport system. The nucleotide sequence of fec revealed five genes, fecABCDE, which are transcribed from fecA to fecE. The fecA gene encodes a previously described outer membrane receptor protein. The fecB gene product is formed as a precursor protein with a signal peptide of 21 amino acids; the mature form, with a molecular weight of 30,815, was previously found in the periplasm. The fecB genes of E. coli B and E. coli K-12 differed in 3 nucleotides, of which 2 gave rise to conservative amino acid exchanges. The fecC and fecD genes were found to encode very hydrophobic polypeptides with molecular weights of 35,367 and 34,148, respectively, both of which are localized in the cytoplasmic membrane. The fecE product was a rather hydrophilic but cytoplasmic membrane-bound protein of Mr 28,189 and contained regions of extensive homology to ATP-binding proteins. The number, structural characteristics, and locations of the FecBCDE proteins were typical for a periplasmic-binding-protein-dependent transport system. It is proposed that after FecA- and TonB-dependent transport of iron(III) dicitrate across the outer membrane, uptake through the cytoplasmic membrane follows the binding-protein-dependent transport mechanism. FecC and FecD exhibited homologies to each other, to the N- and C-terminal halves of FhuB of the iron(III) hydroxamate transport system, and to BtuC of the vitamin B12 transport system. FecB showed some homology to FhuD, suggesting that the latter may function in the same manner as a binding protein in iron(III) hydroxamate transport. The close homology between the proteins of the two iron transport systems and of the vitamin B12 transport system indicates a common evolution for all three systems.

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Selected References

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  • Ames GF. Bacterial periplasmic transport systems: structure, mechanism, and evolution. Annu Rev Biochem. 1986;55:397–425. [PubMed]
  • Amzel LM, Pedersen PL. Proton atpases: structure and mechanism. Annu Rev Biochem. 1983;52:801–824. [PubMed]
  • Bassford PJ, Jr, Bradbeer C, Kadner RJ, Schnaitman CA. Transport of vitamin B12 in tonB mutants of Escherichia coli. J Bacteriol. 1976 Oct;128(1):242–247. [PMC free article] [PubMed]
  • Burkhardt R, Braun V. Nucleotide sequence of the fhuC and fhuD genes involved in iron (III) hydroxamate transport: domains in FhuC homologous to ATP-binding proteins. Mol Gen Genet. 1987 Aug;209(1):49–55. [PubMed]
  • Chou PY, Fasman GD. Empirical predictions of protein conformation. Annu Rev Biochem. 1978;47:251–276. [PubMed]
  • Coulton JW, Mason P, Allatt DD. fhuC and fhuD genes for iron (III)-ferrichrome transport into Escherichia coli K-12. J Bacteriol. 1987 Aug;169(8):3844–3849. [PMC free article] [PubMed]
  • Friedrich MJ, de Veaux LC, Kadner RJ. Nucleotide sequence of the btuCED genes involved in vitamin B12 transport in Escherichia coli and homology with components of periplasmic-binding-protein-dependent transport systems. J Bacteriol. 1986 Sep;167(3):928–934. [PMC free article] [PubMed]
  • Frost GE, Rosenberg H. The inducible citrate-dependent iron transport system in Escherichia coli K12. Biochim Biophys Acta. 1973 Nov 30;330(1):90–101. [PubMed]
  • Hantke K, Braun V. Functional interaction of the tonA/tonB receptor system in Escherichia coli. J Bacteriol. 1978 Jul;135(1):190–197. [PMC free article] [PubMed]
  • Higgins CF, Gallagher MP, Mimmack ML, Pearce SR. A family of closely related ATP-binding subunits from prokaryotic and eukaryotic cells. Bioessays. 1988 Apr;8(4):111–116. [PubMed]
  • Hussein S, Hantke K, Braun V. Citrate-dependent iron transport system in Escherichia coli K-12. Eur J Biochem. 1981 Jul;117(2):431–437. [PubMed]
  • Köster W, Braun V. Iron hydroxamate transport of Escherichia coli: nucleotide sequence of the fhuB gene and identification of the protein. Mol Gen Genet. 1986 Sep;204(3):435–442. [PubMed]
  • Kyte J, Doolittle RF. A simple method for displaying the hydropathic character of a protein. J Mol Biol. 1982 May 5;157(1):105–132. [PubMed]
  • Lugtenberg B, Meijers J, Peters R, van der Hoek P, van Alphen L. Electrophoretic resolution of the "major outer membrane protein" of Escherichia coli K12 into four bands. FEBS Lett. 1975 Oct 15;58(1):254–258. [PubMed]
  • Moffatt BA, Studier FW. T7 lysozyme inhibits transcription by T7 RNA polymerase. Cell. 1987 Apr 24;49(2):221–227. [PubMed]
  • Nakae T. Outer-membrane permeability of bacteria. Crit Rev Microbiol. 1986;13(1):1–62. [PubMed]
  • Nikaido H, Vaara M. Molecular basis of bacterial outer membrane permeability. Microbiol Rev. 1985 Mar;49(1):1–32. [PMC free article] [PubMed]
  • Pressler U, Staudenmaier H, Zimmermann L, Braun V. Genetics of the iron dicitrate transport system of Escherichia coli. J Bacteriol. 1988 Jun;170(6):2716–2724. [PMC free article] [PubMed]
  • Rosenberg M, Court D. Regulatory sequences involved in the promotion and termination of RNA transcription. Annu Rev Genet. 1979;13:319–353. [PubMed]
  • Sanger F, Nicklen S, Coulson AR. DNA sequencing with chain-terminating inhibitors. Proc Natl Acad Sci U S A. 1977 Dec;74(12):5463–5467. [PubMed]
  • Schnaitman CA. Solubilization of the cytoplasmic membrane of Escherichia coli by Triton X-100. J Bacteriol. 1971 Oct;108(1):545–552. [PMC free article] [PubMed]
  • Shine J, Dalgarno L. The 3'-terminal sequence of Escherichia coli 16S ribosomal RNA: complementarity to nonsense triplets and ribosome binding sites. Proc Natl Acad Sci U S A. 1974 Apr;71(4):1342–1346. [PubMed]
  • Studier FW, Moffatt BA. Use of bacteriophage T7 RNA polymerase to direct selective high-level expression of cloned genes. J Mol Biol. 1986 May 5;189(1):113–130. [PubMed]
  • Tabor S, Richardson CC. A bacteriophage T7 RNA polymerase/promoter system for controlled exclusive expression of specific genes. Proc Natl Acad Sci U S A. 1985 Feb;82(4):1074–1078. [PubMed]
  • Wagegg W, Braun V. Ferric citrate transport in Escherichia coli requires outer membrane receptor protein fecA. J Bacteriol. 1981 Jan;145(1):156–163. [PMC free article] [PubMed]
  • Woodrow GC, Langman L, Young IG, Gibson F. Mutations affecting the citrate-dependent iron uptake system in Escherichia coli. J Bacteriol. 1978 Mar;133(3):1524–1526. [PMC free article] [PubMed]
  • Yanisch-Perron C, Vieira J, Messing J. Improved M13 phage cloning vectors and host strains: nucleotide sequences of the M13mp18 and pUC19 vectors. Gene. 1985;33(1):103–119. [PubMed]
  • Zimmermann L, Hantke K, Braun V. Exogenous induction of the iron dicitrate transport system of Escherichia coli K-12. J Bacteriol. 1984 Jul;159(1):271–277. [PMC free article] [PubMed]

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