Mechanism and regulation of synthesis of aerobactin in Escherichia coli K12 (pColV-K30)

The aerobactin operon of the virulence plasmid pColV-K30 of Escherichia coli K12 consists of four genes for biosynthesis and one for transport of the siderophore. Regulation by iron occurs at the transcriptional level and is mediated by a ferrous iron binding protein designated Fur (ferric uptake regulation). The metallated Fur repressor binds at a palindromic dyad, the "iron box" operator, situated in the vicinity of the RNA polymerase attachment site of the promoter. Evidence suggests that the ferrous iron enters the C-terminal domain of Fur to cause a conformational change in the N-terminal part of the protein. This results in greatly enhanced affinity of the repressor for the operator. Key words: aerobactin, enterobactin, Fur repressor, regulation, siderophores, virulence.

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Do FeS clusters rule bacterial iron regulation?

Journal of Biological Chemistry ◽

10.1074/jbc.h120.016190 ◽

2020 ◽

Vol 295 (46) ◽

pp. 15464-15465

Author(s):

Roland Lill

Keyword(s):

Escherichia Coli ◽

Ferrous Iron ◽

Iron Uptake ◽

Iron Regulation ◽

Ferric Uptake Regulator ◽

Iron Binding ◽

Cellular Iron ◽

Open Question ◽

Exciting Possibility

For decades, the bacterial ferric uptake regulator (Fur) has been thought to respond to ferrous iron to transcriptionally regulate genes required for balancing iron uptake, storage, and utilization. Because iron binding to Fur has never been confirmed in vivo, the physiological iron-sensing mechanism remains an open question. Fontenot et al. now show that Fur purified from Escherichia coli binds an all-Cys-coordinated [2Fe-2S] cluster. This finding opens the exciting possibility that Fur may join numerous well-studied bacterial, fungal, and mammalian proteins that use FeS clusters for cellular iron regulation.

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Bacteriostasis ofEscherichia coliby milk. III. The activity and stability of early, transitional and mature human milk collected locally

Journal of Hygiene ◽

10.1017/s0022172400026036 ◽

1979 ◽

Vol 83 (2) ◽

pp. 243-254 ◽

Cited By ~ 3

Author(s):

Pauline Honour ◽

Jean M. Dolby

Keyword(s):

Escherichia Coli ◽

Resistant Strain ◽

Binding Protein ◽

Post Partum ◽

Bacteriostatic Activity ◽

Iron Binding ◽

Early Lactation ◽

E Coli ◽

Progressive Loss ◽

Iron Binding Protein

summaryMilk from 150 local mothers has been assayed for bacteriostatic activity for milk-sensitive and milk-resistant indicator strains ofEscherichia coli. Activity is greatest in colostrum which is active directly against all strains ofE. coli. One week after delivery of the baby, milk is active against the milk-sensitive strain and becomes active against the milk-resistant strain in the presence of physiological amounts of bicarbonate and iron-binding protein. This activity decreases within 2–4 days on keeping milk unheated at 4 °C but is preserved for at least 4 months and often up to 2 years in milk heated to 56 °C then stored at 4 °C or in milk frozen, unheated, at −28 °C provided it is not repeatedly thawed and frozen. Later lactation milks are usually indistinguishable in activity from 1-week post-partum milk but may be less stable on storage particularly if frozen. Lyophilizationin vacuopreserves activity of early-lactation milk for at least 6 months.Heating milk to above 65 °C causes a progressive loss of activity which can be partially restored by adding bicarbonate and iron-binding protein. Iron abolishes the activity of milk and reduces that of colostrum.

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Mobilization of the iron centre in IscA for the iron–sulphur cluster assembly in IscU

Biochemical Journal ◽

10.1042/bj20050405 ◽

2005 ◽

Vol 389 (3) ◽

pp. 797-802 ◽

Cited By ~ 45

Author(s):

Baojin Ding ◽

Edward S. Smith ◽

Huangen Ding

Keyword(s):

Escherichia Coli ◽

Reduced Glutathione ◽

Binding Protein ◽

Iron Binding ◽

Cluster Assembly ◽

Uv Visible ◽

Iron Binding Protein ◽

Epr Measurements

The biogenesis of iron–sulphur clusters requires the co-ordinated delivery of both iron and sulphur. It is now clear that sulphur in iron–sulphur clusters is derived from L-cysteine by cysteine desulphurases. However, the iron donor for the iron–sulphur cluster assembly still remains elusive. Our previous studies indicated that Escherichia coli IscA, a member of the iron–sulphur cluster assembly machinery, is an iron-binding protein that can provide iron for the iron–sulphur cluster assembly in a proposed scaffold IscU. To determine how the iron centre in IscA is transferred for the iron–sulphur cluster assembly in IscU, we explore the mobility of the iron centre in IscA. The UV–visible and EPR measurements show that L-cysteine, but not IscU, is able to mobilize the iron centre in IscA and make the iron available for the iron–sulphur cluster assembly in IscU. Other related biological thiols such as N-acetyl-L-cysteine or reduced glutathione have no effect on the iron centre of IscA, suggesting that L-cysteine is unique in mobilizing the iron centre of IscA. Nevertheless, L-cysteine alone is not sufficient to transfer the iron from IscA to IscU. Both L-cysteine and cysteine desulphurase (IscS) are required for the IscA-mediated assembly of iron–sulphur clusters in IscU. The results suggest that L-cysteine may have two distinct functions in the biogenesis of iron–sulphur clusters: to mobilize the iron centre in IscA and to provide sulphur via cysteine desulphurase (IscS) for the iron–sulphur cluster assembly in IscU.

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Ferrous iron-binding protein Omb of Salmonella enterica serovar Choleraesuis promotes resistance to hydrophobic antibiotics and contributes to its virulence

Microbiology ◽

10.1099/mic.0.026880-0 ◽

2009 ◽

Vol 155 (7) ◽

pp. 2365-2374 ◽

Cited By ~ 8

Author(s):

Jer-Horng Su ◽

Yin-Ching Chung ◽

Hsin-Chun Lee ◽

I-Cheng Tseng ◽

Ming-Chung Chang

Keyword(s):

Outer Membrane ◽

Salmonella Enterica ◽

Ferrous Iron ◽

Binding Protein ◽

Polymyxin B ◽

Iron Binding ◽

Virulence Attenuation ◽

Increased Sensitivity ◽

Iron Binding Protein

Salmonella enterica serovar Choleraesuis (SC) is an important enteric pathogen that causes serious systemic infections in swine and humans. To identify the genes required for resistance to antimicrobial peptides, we constructed a bank of SC transposon mutants and screened them for hypersensitivity to the cationic peptide polymyxin B. Here we report one isolated polymyxin B-susceptible mutant that also exhibited increased sensitivity toward human neutrophil peptide alpha-defensin 1 (HNP-1) and hydrophobic antibiotics including erythromycin and novobiocin. The mutant had a mutation in an ORF identified as outer membrane β-barrel protein gene omb. The purified recombinant Omb protein was characterized as a ferrous iron-binding protein. The constructed omb isogenic mutant grew more slowly in iron-limiting conditions than the wild-type (WT) parent strain. In addition, compared with the WT strain, the omb mutant exhibited an increase in net negative charge upon the cell surface and was more easily killed by polymyxin B, HNP-1 and hydrophobic antibiotics. The omb gene was transcribed, regardless of the iron content within the growth medium, and the Omb protein appeared exclusively in the outer membrane fraction. Infection experiments demonstrated virulence attenuation when the mutant was administered orally or intraperitoneally to mice. This study indicates that Omb is a previously unrecognized ferrous iron-binding protein. In vivo, Omb may be involved in the acquisition of ferrous iron during the initial stages of SC infection and appears to be an important virulence factor for SC in mice.

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Comparison of Ehrlichia chaffeensisRecombinant Proteins for Serologic Diagnosis of Human Monocytotropic Ehrlichiosis

Journal of Clinical Microbiology ◽

10.1128/jcm.37.8.2568-2575.1999 ◽

1999 ◽

Vol 37 (8) ◽

pp. 2568-2575 ◽

Cited By ~ 21

Author(s):

Xue-Jie Yu ◽

Patricia A. Crocquet-Valdes ◽

Louis C. Cullman ◽

Vsevolod L. Popov ◽

David H. Walker

Keyword(s):

Escherichia Coli ◽

Recombinant Protein ◽

Gram Negative Bacteria ◽

Iron Binding ◽

Serum Samples ◽

Gram Negative ◽

Recombinant Antigens ◽

Genes Encoding ◽

Iron Binding Protein ◽

Positive Results

Diagnosis of human monocytotropic ehrlichiosis (HME) generally depends on serology that detects the antibody response to immunodominant proteins of Ehrlichia chaffeensis. Protein immunoblotting was used to evaluate the reaction of the antibodies in patients’ sera with the recombinant E. chaffeensis 120- and 28-kDa proteins as well as the 106- and the 37-kDa proteins. The cloning of the genes encoding the latter two proteins is described in this report. Immunoelectron microscopy demonstrated that the 106-kDa protein is located at the surfaces of ehrlichiae and on the intramorular fibrillar structures associated with E. chaffeensis. The 37-kDa protein is homologous to the iron-binding protein of gram-negative bacteria. Forty-two serum samples from patients who were suspected to have HME were tested by immunofluorescence (IFA) using E. chaffeensis antigen and by protein immunoblotting using recombinant E. chaffeensisproteins expressed in Escherichia coli. Thirty-two serum samples contained IFA antibodies at a titer of 1:64 or greater. The correlation of IFA and recombinant protein immunoblotting was 100% for the 120-kDa protein, 41% for the 28-kDa protein, 9.4% for the 106-kDa protein, and 0% for the 37-kDa protein. None of the recombinant antigens yielded false-positive results. All the sera reactive with the recombinant 28- or the 106-kDa proteins also reacted with the recombinant 120-kDa protein.

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