Relationship between the tonB locus and iron transport in Escherichia coli

Frost, G.E.; Rosenberg, H.

doi:10.1128/jb.124.2.704-712.1975

Cited by 100 publications

(79 citation statements)

References 36 publications

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“…A possible role is suggested, however, by the fact that the 3:1 iron complex formed by 3,4-DHB would be small enough to allow its passage through the outer membrane by simple diffusion. This has been demonstrated using ferrated 2,3-DHB and a strain of Escherichia coli deficient in both enterobactin and an enterobactin outer membrane receptor [18,19]. It is conceivable that the formation and extracelhilar release of 3,4-DHB by Am.…”

Section: Resultsmentioning

confidence: 97%

The isolation and identification of 3,4-dihydroxybenzoic acid formed by nitrogen-fixing Azomonas macrocytogenes

Westervelt

1985

FEMS Microbiology Letters

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Section: Resultsmentioning

confidence: 97%

The isolation and identification of 3,4-dihydroxybenzoic acid formed by nitrogen-fixing Azomonas macrocytogenes

Westervelt

1985

FEMS Microbiology Letters

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“…However, indirect evidence suggests that the ton B function may be located in the outer membrane. Frost and Rosenberg (24) noted that the requirement for the ton B function for growth on extracted, iron-deficient medium could be overcome by added 2,3-dihydroxybenzoate (DHB) or shikimate but not by added enterochelin. There was a further requirement for enterochelin synthesis from these substrates since ent F mutants, which were blocked in enterochelin synthesis from DHB or shikimate, were unable to overcome the requirement for the ton B product for growth on iron-deficient medium.…”

Section: The Ton B Function: the Common Element Of Iron Uptakementioning

confidence: 99%

“…The system which will be described in some detail below consists of products of two localized in the outer membrane (23) and since indirect evidence suggests a similar localization for the ton B function (24), it is likely that both interact to form specific pores through the outer membrane for the iron complexes. The outer membrane is a permeability barrier for substrates with a molecular weight greater than about 700 daltons (25).…”

Section: Introductionmentioning

confidence: 99%

Fuctional organization of the outer membrane of escherichia coli: Phage and colicin receptors as components of iron uptake systems

et al. 1976

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The functional interaction of outer membrane proteins of E. coli can be studied using phage and colicin receptors which are essential components of penetration systems. The uptake of ferric iron in the form of the ferrichrome complex requires the ton A and ton B functions in the outer membrane of E. coli. The ton A gene product is the receptor protein for phage T5 and is required together with the ton B function by the phages T1 and ø80 to infect cells and by colicin M and the antibiotic albomycin, a structural analogue of ferrichrome, to kill cells. The ton B function is necessary for the uptake of ferric iron complexed by citrate. Iron complexed by enterochelin is only transported in the presence of the ton B and feu functions. Cells which have lost the feu function are resistant to the colicins B, I or V while ton B mutants are resistant to all 3 colicins. The interaction of the ton A, ton B, and feu functions apparently permits quite different "substrates" to overcome the permeability barrier of the outer membrane. It was shown for ferrichrome dependent iron uptake that the complexing agent was not altered and could be used repeatedly. Only very low amounts of 3H-labeled ferrichrome were found in the cell. It is possible that the iron is mobilized in the membrane and that desferri-ferrichrome is released into the medium without having entered the cytoplasm. Growth on ferrichrome as the sole iron source was used to select revertants of T5 resistant ton A mutants. All revertants exhibited wild-type properties with the exception of partial revertants. In these 4 strains, as in the ton A mutants, the ton A protein was not detectable by SDS polyacrylamide gel electrophoreses of outer membranes. Albomycin resistant mutants were selected and shown to fall into 5 categories: 1) ton A; 2) ton B mutants; 3) mutants with no iron transport defects and normal ton A/ton B functions, which might be target site mutants; 4) mutants which were deficient in ferrichrome-mediated iron uptake but had normal ton A/ton B functions. We tentatively consider that the defect might be located in the active transport system of the cytoplasmic membrane; 5) a variety of mutants with the following general properties: most of them were resistant to colicin M, transported iron poorly, and, like ton B mutants, contained additional proteins in the outer membrane. The outer membrane protein patterns of wild-type and ton B mutant strains were compared by slab gel electrophoresis in an attempt to identify a ton B protein. It was observed that under most growth conditions, ton B mutants overproduced 3 proteins of molecular weights 74,000-83,000. In extracted, iron-deficient medium, both the wild-type and ton B mutant strains had similar large amounts of these proteins in their outer membranes. The appearance of these proteins was suppressed by excess iron in both wild-type and mutant. From this evidence it is apparent that the proteins appear as a response to low intracellular iron rather than being controlled by the ton B gene...

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“…In addition to the ferric enterobaotin transport system, a number of other iron-chelate transport systems in E. coli have been described, including those for ferric dicitrate [fee) and ferric hydroxamates (fhu). Each of these systems requires an outer membrane receptor protein and depends on the cytoplasmic membrane protein TonB for active transport of the complex across the outer membrane (Frost and Rosenberg. 1975), This functional requirement for TonB also places vitamin Bi2 transport {btu) within this group (Bassford et ai, 1976).…”

Section: Introductionmentioning

confidence: 99%

Nucleotide sequence and genetic organization of the ferric enterobactin transport system: homology to other peripiasmic binding protein‐dependent systems in Escherichia coli

Shea

McIntosh

1991

Molecular Microbiology

129

134

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The nucleotide sequence of the Escherichia coli fep genomic region has been determined. Three new loci were identified. One of these, P43, encodes a membrane protein that is not essential for ferric enterobactin transport. Two others, fepD and fepG, were found to be essential for transport and their translational products showed extensive homology to other integral membrane proteins involved in TonB-dependent transport processes. The FepC amino acid sequence suggested a peripheral membrane location and revealed conserved ATP-binding domains. Together these data indicate that ferric enterobactin is transported through a typical periplasmic binding protein-dependent system. In addition, the transcriptional organization of these genes was examined and primer extension analysis identified a single iron-regulated bidirectional promoter between the P43 gene and the fepDGC operon.

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Relationship between the tonB locus and iron transport in Escherichia coli

Cited by 100 publications

References 36 publications

The isolation and identification of 3,4-dihydroxybenzoic acid formed by nitrogen-fixing Azomonas macrocytogenes

The isolation and identification of 3,4-dihydroxybenzoic acid formed by nitrogen-fixing Azomonas macrocytogenes

Fuctional organization of the outer membrane of escherichia coli: Phage and colicin receptors as components of iron uptake systems

Nucleotide sequence and genetic organization of the ferric enterobactin transport system: homology to other peripiasmic binding protein‐dependent systems in Escherichia coli

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