Transferrin-mediated iron acquisition by pathogenic Neisseria

2002 ◽  
Vol 30 (4) ◽  
pp. 705-707 ◽  
Author(s):  
R. W. Evans ◽  
J. S. Oakhill
Keyword(s):  
Bacterial Cell ◽  
Iron Uptake ◽  
Binding Proteins ◽  
Current Knowledge ◽  
Iron Acquisition ◽  
Direct Interaction ◽  
Acquisition System ◽  
Uptake System ◽  
Short Account ◽  
Transferrin Binding Proteins

The pathogenic Neisseria have a siderophore-independent iron-uptake system reliant on a direct interaction between the bacterial cell and transferrin. In the meningococcus this uptake system is dependent on two surface-exposed transferrin-binding proteins. This short account will review our current knowledge of the transferrin-mediated iron-acquisition system of pathogenic Neisseria.

scholarly journals Identification of TbpA Residues Required for Transferrin-Iron Utilization by Neisseria gonorrhoeae

2008 ◽  
Vol 76 (5) ◽  
pp. 1960-1969 ◽  
Author(s):  
Jennifer M. Noto ◽  
Cynthia Nau Cornelissen
Keyword(s):  
Neisseria Gonorrhoeae ◽  
Iron Uptake ◽  
Binding Proteins ◽  
Iron Acquisition ◽  
Uptake System ◽  
Wild Type ◽  
Conserved Motif ◽  
Alanine Substitution ◽  
Transferrin Binding Proteins ◽  
Iron Utilization

ABSTRACT Neisseria gonorrhoeae requires iron for survival in the human host and therefore expresses high-affinity receptors for iron acquisition from host iron-binding proteins. The gonococcal transferrin-iron uptake system is composed of two transferrin binding proteins, TbpA and TbpB. TbpA is a TonB-dependent, outer membrane transporter critical for iron acquisition, while TbpB is a surface-exposed lipoprotein that increases the efficiency of iron uptake. The precise mechanism by which TbpA mediates iron acquisition has not been elucidated; however, the process is distinct from those of characterized siderophore transporters. Similar to these TonB-dependent transporters, TbpA is proposed to have two distinct domains, a β-barrel and a plug domain. We hypothesize that the TbpA plug coordinates iron and therefore potentially functions in multiple steps of transferrin-mediated iron acquisition. To test this hypothesis, we targeted a conserved motif within the TbpA plug domain and generated single, double, and triple alanine substitution mutants. Mutagenized TbpAs were expressed on the gonococcal cell surface and maintained wild-type transferrin binding affinity. Single alanine substitution mutants internalized iron at wild-type levels, while the double and triple mutants showed a significant decrease in iron uptake. Moreover, the triple alanine substitution mutant was unable to grow on transferrin as a sole iron source; however, expression of TbpB compensated for this defect. These data indicate that the conserved motif between residues 120 and 122 of the TbpA plug domain is critical for transferrin-iron utilization, suggesting that this region plays a role in iron acquisition that is shared by both TbpA and TbpB.

scholarly journals Expression and purification of functional recombinant meningococcal transferrin-binding protein A

2002 ◽  
Vol 364 (3) ◽  
pp. 613-616 ◽  
Author(s):  
Jonathan S. OAKHILL ◽  
Christopher L. JOANNOU ◽  
Susan K. BUCHANAN ◽  
Andrew R. GORRINGE ◽  
Robert W. EVANS
Keyword(s):  
Iron Uptake ◽  
Pathogenic Bacteria ◽  
Protein A ◽  
Direct Interaction ◽  
Uptake System ◽  
Meningococcal Vaccine ◽  
Expression And Purification ◽  
Receptor Interactions ◽  
Gated Channel ◽  
Transferrin Binding Proteins

Pathogenic bacteria of the genus Neisseria have a siderophore-independent iron-uptake system reliant on a direct interaction between the bacterial cell and human transferrin (hTf), a serum protein. In the meningococcus, this uptake system is dependent on two surface-exposed, transferrin-binding proteins (Tbps), TbpA and TbpB. TbpA is highly conserved among meningococcal strains, and is thought to be a porin-like integral protein that functions as a gated channel for the passage of iron into the periplasm. TbpB is more variable in size, lipidated and fully surface-exposed. Given its location on the cell surface, its role in pathogenicity and interstrain sequence conservation, TbpA is currently being regarded for inclusion in a meningococcal vaccine effective against all serogroups. This requires gaining knowledge of the ligand—receptor interactions. In the present study we have optimized a procedure for obtaining purified, functionally active recombinant TbpA at a level and stability necessary for the initiation of such studies.

scholarly journals Conserved Regions of Gonococcal TbpB Are Critical for Surface Exposure and Transferrin Iron Utilization

2013 ◽  
Vol 81 (9) ◽  
pp. 3442-3450 ◽  
Author(s):  
Karen L. Ostberg ◽  
Amanda J. DeRocco ◽  
Shreni D. Mistry ◽  
Mary Kathryne Dickinson ◽  
Cynthia Nau Cornelissen
Keyword(s):  
Iron Uptake ◽  
Cell Envelope ◽  
Iron Acquisition ◽  
Site Directed Mutagenesis ◽  
Uptake System ◽  
Content Type ◽  
Functional Roles ◽  
Conserved Regions ◽  
Transferrin Binding Proteins ◽  
Iron Utilization

ABSTRACTThe transferrin-binding proteins TbpA and TbpB enableNeisseria gonorrhoeaeto obtain iron from human transferrin. The lipoprotein TbpB facilitates, but is not strictly required for, TbpA-mediated iron acquisition. The goal of the current study was to determine the contribution of two conserved regions within TbpB to the function of this protein. Using site-directed mutagenesis, the first mutation we constructed replaced the lipobox (LSAC) of TbpB with a signal I peptidase cleavage site (LAAA), while the second mutation deleted a conserved stretch of glycine residues immediately downstream of the lipobox. We then evaluated the resulting mutants for effects on TbpB expression, surface exposure, and transferrin iron utilization. Western blot analysis and palmitate labeling indicated that the lipobox, but not the glycine-rich motif, is required for lipidation of TbpB and tethering to the outer membrane. TbpB was released into the supernatant by the mutant that produces TbpB LSAC. Neither mutation disrupted the transport of TbpB across the bacterial cell envelope. When these mutant TbpB proteins were produced in a strain expressing a form of TbpA that requires TbpB for iron acquisition, growth on transferrin was either abrogated or dramatically diminished. We conclude that surface tethering of TbpB is required for optimal performance of the transferrin iron acquisition system, while the presence of the polyglycine stretch near the amino terminus of TbpB contributes significantly to transferrin iron transport function. Overall, these results provide important insights into the functional roles of two conserved motifs of TbpB, enhancing our understanding of this critical iron uptake system.

scholarly journals Iron Acquisition in Mycobacterium avium subsp. paratuberculosis

2015 ◽  
Vol 198 (5) ◽  
pp. 857-866 ◽  
Author(s):  
Joyce Wang ◽  
Jalal Moolji ◽  
Alex Dufort ◽  
Alfredo Staffa ◽  
Pilar Domenech ◽  
...  
Keyword(s):  
Mycobacterium Avium ◽  
Iron Uptake ◽  
Genomic Island ◽  
Iron Acquisition ◽  
Laboratory Data ◽  
Uptake System ◽  
Intracellular Iron ◽  
Content Type ◽  
Iron Uptake System ◽  
Environmental Bacterium

ABSTRACTMycobacterium aviumsubsp.paratuberculosisis a host-adapted pathogen that evolved from the environmental bacteriumM. aviumsubsp.hominissuisthrough gene loss and gene acquisition. Growth ofM. aviumsubsp.paratuberculosisin the laboratory is enhanced by supplementation of the media with the iron-binding siderophore mycobactin J. Here we examined the production of mycobactins by related organisms and searched for an alternative iron uptake system inM. aviumsubsp.paratuberculosis. Through thin-layer chromatography and radiolabeled iron-uptake studies, we showed thatM. aviumsubsp.paratuberculosisis impaired for both mycobactin synthesis and iron acquisition. Consistent with these observations, we identified several mutations, including deletions, inM. aviumsubsp.paratuberculosisgenes coding for mycobactin synthesis. Using a transposon-mediated mutagenesis screen conditional on growth without myobactin, we identified a potential mycobactin-independent iron uptake system on aM. aviumsubsp.paratuberculosis-specific genomic island, LSPP15. We obtained a transposon (Tn) mutant with a disruption in the LSPP15 geneMAP3776cfor targeted study. The mutant manifests increased iron uptake as well as intracellular iron content, with genes downstream of the transposon insertion (MAP3775ctoMAP3772c[MAP3775-2c]) upregulated as the result of a polar effect. As an independent confirmation, we observed the same iron uptake phenotypes by overexpressingMAP3775-2cin wild-typeM. aviumsubsp.paratuberculosis. These data indicate that the horizontally acquired LSPP15 genes contribute to iron acquisition byM. aviumsubsp.paratuberculosis, potentially allowing the subsequent loss of siderophore production by this pathogen.IMPORTANCEMany microbes are able to scavenge iron from their surroundings by producing iron-chelating siderophores. One exception isMycobacterium aviumsubsp.paratuberculosis, a fastidious, slow-growing animal pathogen whose growth needs to be supported by exogenous mycobacterial siderophore (mycobactin) in the laboratory. Data presented here demonstrate that, compared to other closely relatedM. aviumsubspecies, mycobactin production and iron uptake are different inM. aviumsubsp.paratuberculosis, and these phenotypes may be caused by numerous deletions in its mycobactin biosynthesis pathway. Using a genomic approach, supplemented by targeted genetic and biochemical studies, we identified that LSPP15, a horizontally acquired genomic island, may encode an alternative iron uptake system. These findings shed light on the potential physiological consequence of horizontal gene transfer inM. aviumsubsp.paratuberculosisevolution.

scholarly journals Gonococcal Genes Encoding Transferrin-Binding Proteins A and B Are Arranged in a Bicistronic Operon but Are Subject to Differential Expression

2001 ◽  
Vol 69 (10) ◽  
pp. 6336-6347 ◽  
Author(s):  
Chalinee Ronpirin ◽  
Ann E. Jerse ◽  
Cynthia Nau Cornelissen
Keyword(s):  
Binding Proteins ◽  
Iron Acquisition ◽  
Sole Source ◽  
Mrna Levels ◽  
Rt Pcr ◽  
Upstream Promoter ◽  
Genes Encoding ◽  
Transferrin Binding Proteins ◽  
Iron Binding Proteins ◽  
Fusion Analysis

ABSTRACT Neisseria gonorrhoeae is capable of utilizing host iron-binding proteins, such as transferrin, lactoferrin, and hemoglobin, as the sole source of iron. The receptor involved in transferrin iron acquisition is composed of two distinct transferrin-binding proteins, TbpA and TbpB. The genes that encode these proteins are linked on the chromosome in the ordertbpB-tbpA but are separated by an inverted repeat of unknown function. In this study, we sought to understand the transcriptional organization and regulation of thetbp genes, using a combination of lacZtranscriptional fusion analysis and reverse transcriptase PCR (RT-PCR). First, we demonstrated that tbpB and tbpAare cotranscribed and coregulated from the common upstream promoter that precedes tbpB. Using β-galactosidase activity as a surrogate for tbp-specific transcription, we found that tbpB-specific transcripts were more prevalent thantbpA-specific transcripts after 2 h of growth under iron stress conditions. We confirmed the results obtained by fusion analysis by using RT-PCR applied to native RNA isolated from wild-type gonococci. Three different varieties of RT-PCR were employed: relative, competitive, and real time quantitative. The results of all analyses indicated that tbpB-specific transcripts were approximately twofold more prevalent than tbpA-specific transcripts at steady state. In iron-stressed cultures, the ratio oftbpB- to tbpA-specific message was approximately 2; however, in iron-replete cultures, this ratio dropped to 1. Using these techniques, we also quantitated the effects of iron, external pH, and presence of ligand on tbp mRNA levels.

Growth characteristics and expression of iron-regulated outer-membrane proteins of chemostat-grown biofilm cells of Pseudomonas aeruginosa

1991 ◽  
Vol 37 (10) ◽  
pp. 737-743 ◽  
Author(s):  
H. Anwar ◽  
J. L. Strap ◽  
J. W. Costerton
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Membrane Proteins ◽  
Dilution Rate ◽  
Outer Membrane ◽  
Iron Uptake ◽  
Iron Acquisition ◽  
Outer Membrane Proteins ◽  
Uptake System ◽  
Planktonic Cells

An in vitro chemostat system was used to study the growth and the expression of iron-regulated outer-membrane proteins (IROMPs) by biofilm cells of Pseudomonas aeruginosa cultivated under conditions of iron limitation. The population of the planktonic cells decreased when the dilution rate was increased. At a dilution rate of 0.05 h−1 the populations of planktonic cells of both mucoid and nonmucoid P. aeruginosa were 3 × 109 cells/mL. This value dropped to 5 × 106 cells/mL when the dilution rate was increased to 1.0 h−1. The reverse was observed for the biofilm cells. The number of biofilm cells colonising the silicone tubing increased when the dilution rate was increased. The number of biofilm cells of the mucoid strain at steady state was 2 × 108 cells/cm (length) when the dilution rate was fixed at 0.05 h−1. The figure increased to 8 × 109 cells/cm when the dilution rate was increased to 1.0 h−1. The population of biofilm cells of the nonmucoid strain was 9 × 107 cells/cm (length) when the dilution rate was 0.05 h−1. It increased to 2 × 109 cells/cm when the dilution rate was set at 1.0 h−1. The expression of IROMPs was induced in the biofilm cells of both mucoid and nonmucoid strains when the dilution rates were 0.05 and 0.2 h−1. IROMPs were reduced but still detectable at the dilution rate of 0.5 h−1. However, the expression of IROMPs was repressed when the dilution rate was increased to 1.0 h−1. The data suggest that the biofilm cells of P. aeruginosa switch on the expression of IROMPs to assist iron acquisition when the dilution rate used for the chemostat run is below 0.5 h−1. The high affinity iron uptake system is not required by the biofilm cells when the dilution rate is increased because the trace amount of iron present in the chemostat is sufficient for the growth of adherent biofilm cells. Key words: Pseudomonas aeruginosa, chemostat, iron, outer-membrane proteins, biofilm.

scholarly journals Iron acquisition system of Sphingobium sp. strain SYK-6, a degrader of lignin-derived aromatic compounds

2020 ◽  
Author(s):  
Masaya Fujita ◽  
Taichi Sakumoto ◽  
Kenta Tanatani ◽  
Hong Yang Yu ◽  
Kosuke Mori ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Aromatic Compounds ◽  
Iron Uptake ◽  
Iron Acquisition ◽  
Essential Element ◽  
Acquisition System ◽  
Bacterial Degradation ◽  
Iron Acquisition System ◽  
Iron Transporter ◽  
Outer Membrane Transporters

AbstractIron, an essential element for all organisms, acts as a cofactor of enzymes in bacterial degradation of recalcitrant aromatic compounds. The bacterial family, Sphingomonadaceae comprises various degraders of recalcitrant aromatic compounds; however, little is known about their iron acquisition system. Here, we investigated the iron acquisition system in a model bacterium capable of degrading lignin-derived aromatics, Sphingobium sp. strain SYK-6. Analyses of SYK-6 mutants revealed that FiuA (SLG_34550), a TonB-dependent receptor (TBDR), was the major outer membrane iron transporter. Three other TBDRs encoded by SLG_04340, SLG_04380, and SLG_10860 also participated in iron uptake, and tonB2 (SLG_34550), one of the six tonB comprising the Ton complex which enables TBDR-mediated transport was critical for iron uptake. The ferrous iron transporter FeoB (SLG_36840) played an important role in iron uptake across the inner membrane. The promoter activities of most of the iron uptake genes were induced under iron-limited conditions, and their regulation is controlled by SLG_29410 encoding the ferric uptake regulator, Fur. Although feoB, among all the iron uptake genes identified is highly conserved in Sphingomonad strains, the outer membrane transporters seem to be diversified. Elucidation of the iron acquisition system promises better understanding of the bacterial degradation mechanisms of aromatic compounds.

Characterization of the iron transporter DMT1 (NRAMP2/DCT1) in red blood cells of normal and anemic mk/mkmice

Blood ◽  
2001 ◽  
Vol 98 (13) ◽  
pp. 3823-3830 ◽  
Author(s):  
François Canonne-Hergaux ◽  
An-Sheng Zhang ◽  
Prem Ponka ◽  
Philippe Gros
Keyword(s):  
Iron Uptake ◽  
Iron Acquisition ◽  
Uptake System ◽  
Erythroid Cells ◽  
Iron Release ◽  
Loss Of Function ◽  
Divalent Metal Transporter 1 ◽  
Peripheral Tissues ◽  
Divalent Metal Transporter ◽  
In Erythroid Cells

Abstract Divalent metal transporter 1 (DMT1) is the major transferrin-independent iron uptake system at the apical pole of intestinal cells, but it may also transport iron across the membrane of acidified endosomes in peripheral tissues. Iron transport and expression of the 2 isoforms of DMT1 was studied in erythroid cells that consume large quantities of iron for biosynthesis of hemoglobin. In mk/mk mice that express a loss-of-function mutant variant of DMT1, reticulocytes have a decreased cellular iron uptake and iron incorporation into heme. Interestingly, iron release from transferrin inside the endosome is normal in mk/mkreticulocytes, suggesting a subsequent defect in Fe++ transport across the endosomal membrane. Studies by immunoblotting using membrane fractions from peripheral blood or spleen from normal mice where reticulocytosis was induced by erythropoietin (EPO) or phenylhydrazine (PHZ) treatment suggest that DMT1 is coexpressed with transferrin receptor (TfR) in erythroid cells. Coexpression of DMT1 and TfR in reticulocytes was also detected by double immunofluorescence and confocal microscopy. Experiments with isoform-specific anti-DMT1 antiserum strongly suggest that it is the non–iron-response element containing isoform II of DMT1 that is predominantly expressed by the erythroid cells. As opposed to wild-type reticulocytes, mk/mk reticulocytes express little if any DMT1, despite robust expression of TfR, suggesting a possible effect of the mutation on stability and targeting of DMT1 isoform II in these cells. Together, these results provide further evidence that DMT1 plays a central role in iron acquisition via the transferrin cycle in erythroid cells.

scholarly journals Iron acquisition system of Sphingobium sp. strain SYK-6, a degrader of lignin-derived aromatic compounds

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Masaya Fujita ◽  
Taichi Sakumoto ◽  
Kenta Tanatani ◽  
HongYang Yu ◽  
Kosuke Mori ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Aromatic Compounds ◽  
Iron Uptake ◽  
Iron Acquisition ◽  
Essential Element ◽  
Acquisition System ◽  
Bacterial Degradation ◽  
Iron Acquisition System ◽  
Iron Transporter ◽  
Outer Membrane Transporters

Abstract Iron, an essential element for all organisms, acts as a cofactor of enzymes in bacterial degradation of recalcitrant aromatic compounds. The bacterial family, Sphingomonadaceae comprises various degraders of recalcitrant aromatic compounds; however, little is known about their iron acquisition system. Here, we investigated the iron acquisition system in a model bacterium capable of degrading lignin-derived aromatics, Sphingobium sp. strain SYK-6. Analyses of SYK-6 mutants revealed that FiuA (SLG_34550), a TonB-dependent receptor (TBDR), was the major outer membrane iron transporter. Three other TBDRs encoded by SLG_04340, SLG_04380, and SLG_10860 also participated in iron uptake, and tonB2 (SLG_34540), one of the six tonB comprising the Ton complex which enables TBDR-mediated transport was critical for iron uptake. The ferrous iron transporter FeoB (SLG_36840) played an important role in iron uptake across the inner membrane. The promoter activities of most of the iron uptake genes were induced under iron-limited conditions, and their regulation is controlled by SLG_29410 encoding the ferric uptake regulator, Fur. Although feoB, among all the iron uptake genes identified is highly conserved in Sphingomonad strains, the outer membrane transporters seem to be diversified. Elucidation of the iron acquisition system promises better understanding of the bacterial degradation mechanisms of aromatic compounds.

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