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.

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.

Evidence for a copper-dependent iron transport system in the marine, magnetotactic bacterium strain MV-1

Microbiology ◽  
2004 ◽  
Vol 150 (9) ◽  
pp. 2931-2945 ◽  
Author(s):  
Bradley L. Dubbels ◽  
Alan A. DiSpirito ◽  
John D. Morton ◽  
Jeremy D. Semrau ◽  
J. N. E. Neto ◽  
...  
Keyword(s):  
Iron Content ◽  
Iron Uptake ◽  
Iron Transport ◽  
Dna Analysis ◽  
Iron Concentration ◽  
Protein A ◽  
Uptake System ◽  
Iron Uptake System ◽  
Cellular Iron ◽  
Solid Media

Cells of the magnetotactic marine vibrio, strain MV-1, produce magnetite-containing magnetosomes when grown anaerobically or microaerobically. Stable, spontaneous, non-magnetotactic mutants were regularly observed when cells of MV-1 were cultured on solid media incubated under anaerobic or microaerobic conditions. Randomly amplified polymorphic DNA analysis showed that these mutants are not all genetically identical. Cellular iron content of one non-magnetotactic mutant strain, designated MV-1nm1, grown anaerobically, was ∼20- to 80-fold less than the iron content of wild-type (wt) MV-1 for the same iron concentrations, indicating that MV-1nm1 is deficient in some form of iron uptake. Comparative protein profiles of the two strains showed that MV-1nm1 did not produce several proteins produced by wt MV-1. To understand the potential roles of these proteins in iron transport better, one of these proteins was purified and characterized. This protein, a homodimer with an apparent subunit mass of about 19 kDa, was an iron-regulated, periplasmic protein (p19). Two potential ‘copper-handling’ motifs (MXM/MX2M) are present in the amino acid sequence of p19, and the native protein binds copper in a 1 : 1 ratio. The structural gene for p19, chpA (copper handling protein) and two other putative genes upstream of chpA were cloned and sequenced. These putative genes encode a protein similar to the iron permease, Ftr1, from the yeast Saccharomyces cerevisiae, and a ferredoxin-like protein of unknown function. A periplasmic, copper-containing, iron(II) oxidase was also purified from wt MV-1 and MV-1nm1. This enzyme, like p19, was regulated by media iron concentration and contained four copper atoms per molecule of enzyme. It is hypothesized that ChpA, the iron permease and the iron(II) oxidase might have analogous functions for the three components of the S. cerevisiae copper-dependent high-affinity iron uptake system (Ctr1, Ftr1 and Fet3, respectively), and that strain MV-1 may have a similar iron uptake system. However, iron(II) oxidase purified from both wt MV-1 and MV-1nm1 displayed comparable iron oxidase activities using O2 as the electron acceptor, indicating that ChpA does not supply the multi-copper iron(II) oxidase with copper.

scholarly journals Identification of Discrete Domains within Gonococcal Transferrin-Binding Protein A That Are Necessary for Ligand Binding and Iron Uptake Functions

2000 ◽  
Vol 68 (12) ◽  
pp. 6988-6996 ◽  
Author(s):  
Ian C. Boulton ◽  
Mary Kate Yost ◽  
James E. Anderson ◽  
Cynthia Nau Cornelissen
Keyword(s):  
Ligand Binding ◽  
Iron Uptake ◽  
Binding Protein ◽  
Protein A ◽  
Ligand Interaction ◽  
Whole Cells ◽  
Affinity Ligand ◽  
Discrete Domains ◽  
Transferrin Binding Proteins

ABSTRACT The availability of free iron in vivo is strictly limited, in part by the iron-binding protein transferrin. The pathogenicNeisseria spp. can sequester iron from this protein, dependent upon two iron-repressible, transferrin-binding proteins (TbpA and TbpB). TbpA is a TonB-dependent, integral, outer membrane protein that may form a β-barrel exposing multiple surface loops, some of which are likely to contain ligand-binding motifs. In this study we propose a topological model of gonococcal TbpA and then test some of the hypotheses set forth by the model by individually deleting three putative loops (designated loops 4, 5, and 8). Each mutant TbpA could be expressed without toxicity and was surface exposed as assessed by immunoblotting, transferrin binding, and protease accessibility. Deletion of loop 4 or loop 5 abolished transferrin binding to whole cells in solid- and liquid-phase assays, while deletion of loop 8 decreased the affinity of the receptor for transferrin without affecting the copy number. Strains expressing any of the three mutated TbpAs were incapable of growth on transferrin as a sole iron source. These data implicate putative loops 4 and 5 as critical determinants for receptor function and transferrin-iron uptake by gonococcal TbpA. The phenotype of the ΔL8TbpA mutant suggests that high-affinity ligand interaction is required for transferrin-iron internalization.

Steric and allosteric factors prevent simultaneous binding of transferrin-binding proteins A and B to transferrin

2012 ◽  
Vol 444 (2) ◽  
pp. 189-197 ◽  
Author(s):  
Leslie P. Silva ◽  
Rong-hua Yu ◽  
Charles Calmettes ◽  
Xue Yang ◽  
Trevor F. Moraes ◽  
...  
Keyword(s):  
Binding Site ◽  
Binding Protein ◽  
Iron Acquisition ◽  
Protein A ◽  
Structural Instability ◽  
Gated Channel ◽  
Surface Receptor ◽  
Hydrogen Deuterium ◽  
Study Support ◽  
Transferrin Binding Proteins

The ability to acquire iron directly from host Tf (transferrin) is an adaptation common to important bacterial pathogens belonging to the Pasteurellaceae, Moraxellaceae and Neisseriaceae families. A surface receptor comprising an integral outer membrane protein, TbpA (Tf-binding protein A), and a surface-exposed lipoprotein, TbpB (Tf-binding protein B), mediates the iron acquisition process. TbpB is thought to extend from the cell surface for capture of Tf to initiate the process and deliver Tf to TbpA. TbpA functions as a gated channel for the passage of iron into the periplasm. In the present study we have mapped the effect of TbpA from Actinobacillus pleuropneumoniae on pTf (porcine Tf) using H/DX-MS (hydrogen/deuterium exchange coupled to MS) and compare it with a previously determined binding site for TbpB. The proposed TbpA footprint is adjacent to and potentially overlapping the TbpB-binding site, and induces a structural instability in the TbpB site. This suggests that simultaneous binding to pTf by both receptors would be hindered. We demonstrate that a recombinant TbpB lacking a portion of its anchor peptide is unable to form a stable ternary TbpA–pTf–TbpB complex. This truncated TbpB does not bind to a preformed Tf–TbpA complex, and TbpA removes pTf from a preformed Tf–TbpB complex. Thus the results of the present study support a model whereby TbpB ‘hands-off’ pTf to TbpA, which completes the iron removal and transport process.

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 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 Antigenic and Sequence Diversity in Gonococcal Transferrin-Binding Protein A

2000 ◽  
Vol 68 (8) ◽  
pp. 4725-4735 ◽  
Author(s):  
Cynthia Nau Cornelissen ◽  
James E. Anderson ◽  
Ian C. Boulton ◽  
P. Frederick Sparling
Keyword(s):  
Synthetic Peptides ◽  
Pathogenic Bacteria ◽  
Binding Proteins ◽  
Specific Binding ◽  
Protein A ◽  
Sequence Diversity ◽  
Western Blots ◽  
Gram Negative ◽  
Genes Encoding ◽  
Transferrin Binding Proteins

ABSTRACT Neisseria gonorrhoeae is a gram-negative pathogen that is capable of satisfying its iron requirement with human iron-binding proteins such as transferrin and lactoferrin. Transferrin-iron utilization involves specific binding of human transferrin at the cell surface to what is believed to be a complex of two iron-regulated, transferrin-binding proteins, TbpA and TbpB. The genes encoding these proteins have been cloned and sequenced from a number of pathogenic, gram-negative bacteria. In the current study, we sequenced four additional tbpA genes from other N. gonorrhoeaestrains to begin to assess the sequence diversity among gonococci. We compared these sequences to those from other pathogenic bacteria to identify conserved regions that might be important for the structure and function of these receptors. We generated polyclonal mouse sera against synthetic peptides deduced from the TbpA sequence from gonococcal strain FA19. Most of these synthetic peptides were predicted to correspond to surface-exposed regions of TbpA. We found that, while most reacted with denatured TbpA in Western blots, only one antipeptide serum reacted with native TbpA in the context of intact gonococci, consistent with surface exposure of the peptide to which this serum was raised. In addition, we evaluated a panel of gonococcal strains for antigenic diversity using these antipeptide sera.

scholarly journals Surfactant protein D binding to alveolar macrophages

1994 ◽  
Vol 300 (1) ◽  
pp. 237-242 ◽  
Author(s):  
K Miyamura ◽  
L E A Leigh ◽  
J Lu ◽  
J Hopkin ◽  
A López Bernal ◽  
...  
Keyword(s):  
Alveolar Macrophages ◽  
Serum Proteins ◽  
Specific Binding ◽  
Lectin Binding ◽  
Protein A ◽  
Direct Interaction ◽  
Surfactant Protein ◽  
Lung Epithelial Cells ◽  
Surfactant Protein D ◽  
Apparent Dissociation Constant

Surfactant protein D (SP-D) is a lung-specific protein, synthesized and secreted by lung epithelial cells. It belongs to group III of the family of C-type lectins; each member of this group has an unusual overall structure consisting of multiple globular ‘head’ regions (which contain the C-type lectin domains) linked by triple-helical, collagen-like, strands. This group includes the surfactant protein A (SP-A) and the serum proteins mannan-binding protein, conglutinin and collectin-43, all of which have been shown to bind to the C1q receptor found on a wide variety of cells, including macrophages. Both SP-D and SP-A have been shown to enhance oxygen radical production by alveolar macrophages. Although this strongly suggests a direct interaction between SP-D and a specific receptor on alveolar macrophages, it is still unclear whether SP-D binds to the same receptor used by SP-A and/or C1q. Human SP-D was isolated from amniotic fluid and was radiolabelled using 125I. Alveolar macrophages were isolated from human bronchioalveolar lavage fluid, and also from bovine lung washings, by differential adhesion to 24-well tissue-culture plates. The study was carried out using EDTA-containing buffers, to eliminate Ca(2+)-dependent C-type lectin binding, and was also carried out at 4 degrees C to eliminate possible internalization by the cells. 125I-SP-D showed specific binding to alveolar macrophages in both a time- and concentration-saturable manner. The binding was inhibited, by approx. 90%, on addition of a 200-fold excess of unlabelled SP-D. The apparent dissociation constant (Kd) was (3.6 +/- 1.3) x 10(-11) M, based on the assumption that native SP-D is assembled as a dodecamer of 12 identical polypeptides of 43 kDa to yield a protein of 516 kDa. C1q was also shown to bind alveolar macrophages (Kd 3 x 10(-6) M), but addition of C1q did not show inhibition of the binding of 125I-SP-D to the macrophages. We conclude that SP-D binds specifically to alveolar macrophages and the receptor involved is different from that utilized by C1q.

scholarly journals Positive Regulation of fur Gene Expression via Direct Interaction of Fur in a Pathogenic Bacterium, Vibrio vulnificus

2007 ◽  
Vol 189 (7) ◽  
pp. 2629-2636 ◽  
Author(s):  
Hyun-Jung Lee ◽  
So Hyun Bang ◽  
Kyu-Ho Lee ◽  
Soon-Jung Park
Keyword(s):  
Gene Expression ◽  
Pathogenic Bacteria ◽  
Vibrio Vulnificus ◽  
Iron Concentration ◽  
Direct Interaction ◽  
Repeated Sequence ◽  
Upstream Region ◽  
Fur Protein

ABSTRACT In pathogenic bacteria, the ability to acquire iron, which is mainly regulated by the ferric uptake regulator (Fur), is essential to maintain growth as well as its virulence. In Vibrio vulnificus, a human pathogen causing gastroenteritis and septicemia, fur gene expression is positively regulated by Fur when the iron concentration is limited (H.-J. Lee et al., J. Bacteriol. 185:5891-5896, 2003). Footprinting analysis revealed that an upstream region of the fur gene was protected by the Fur protein from DNase I under iron-depleted conditions. The protected region, from −142 to −106 relative to the transcription start site of the fur gene, contains distinct AT-rich repeats. Mutagenesis of this repeated sequence resulted in abolishment of binding by Fur. To confirm the role of this cis-acting element in Fur-mediated control of its own gene in vivo, fur expression was monitored in V. vulnificus strains using a transcriptional fusion containing the mutagenized Fur-binding site (fur mt::luxAB). Expression of fur mt::luxAB showed that it was not regulated by Fur and was not influenced by iron concentration. Therefore, this study demonstrates that V. vulnificus Fur acts as a positive regulator under iron-limited conditions by direct interaction with the fur upstream region.

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