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Nahar N, Turni C, Tram G, Blackall PJ, Atack JM. Actinobacillus pleuropneumoniae: The molecular determinants of virulence and pathogenesis. Adv Microb Physiol 2021; 78:179-216. [PMID: 34147185 DOI: 10.1016/bs.ampbs.2020.12.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Actinobacillus pleuropneumoniae, the causative agent of porcine pleuropneumonia, is responsible for high economic losses in swine herds across the globe. Pleuropneumonia is characterized by severe respiratory distress and high mortality. The knowledge about the interaction between bacterium and host within the porcine respiratory tract has improved significantly in recent years. A. pleuropneumoniae expresses multiple virulence factors, which are required for colonization, immune clearance, and tissue damage. Although vaccines are used to protect swine herds against A. pleuropneumoniae infection, they do not offer complete coverage, and often only protect against the serovar, or serovars, used to prepare the vaccine. This review will summarize the role of individual A. pleuropneumoniae virulence factors that are required during key stages of pathogenesis and disease progression, and highlight progress made toward developing effective and broadly protective vaccines against an organism of great importance to global agriculture and food production.
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Affiliation(s)
- Nusrat Nahar
- Institute for Glycomics, Griffith University, Gold Coast, QLD, Australia
| | - Conny Turni
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, QLD, Australia
| | - Greg Tram
- Institute for Glycomics, Griffith University, Gold Coast, QLD, Australia
| | - Patrick J Blackall
- Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, QLD, Australia.
| | - John M Atack
- Institute for Glycomics, Griffith University, Gold Coast, QLD, Australia.
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2
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Abstract
Capnocytophaga canimorsus, a dog mouth commensal and a member of the Bacteroidetes phylum, causes rare but often fatal septicemia in humans that have been in contact with a dog. Here, we show that C. canimorsus strains isolated from human infections grow readily in heat-inactivated human serum and that this property depends on a typical polysaccharide utilization locus (PUL), namely, PUL3 in strain Cc5. PUL are a hallmark of Bacteroidetes, and they encode various products, including surface protein complexes that capture and process polysaccharides or glycoproteins. The archetype system is the Bacteroides thetaiotaomicron Sus system, devoted to starch utilization. Unexpectedly, PUL3 conferred the capacity to acquire iron from serotransferrin (STF), and this capacity required each of the seven encoded proteins, indicating that a whole Sus-like machinery is acting as an iron capture system (ICS), a new and unexpected function for Sus-like machinery. No siderophore could be detected in the culture supernatant of C. canimorsus, suggesting that the Sus-like machinery captures iron directly from transferrin, but this could not be formally demonstrated. The seven genes of the ICS were found in the genomes of several opportunistic pathogens from the Capnocytophaga and Prevotella genera, in different isolates of the severe poultry pathogen Riemerella anatipestifer, and in strains of Bacteroides fragilis and Odoribacter splanchnicus isolated from human infections. Thus, this study describes a new type of ICS that evolved in Bacteroidetes from a polysaccharide utilization system and most likely represents an important virulence factor in this group.
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Conserved regions of gonococcal TbpB are critical for surface exposure and transferrin iron utilization. Infect Immun 2013; 81:3442-50. [PMID: 23836816 DOI: 10.1128/iai.00280-13] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The transferrin-binding proteins TbpA and TbpB enable Neisseria gonorrhoeae to 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.
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Banerjee S, Farhana A, Ehtesham NZ, Hasnain SE. Iron acquisition, assimilation and regulation in mycobacteria. INFECTION GENETICS AND EVOLUTION 2011; 11:825-38. [PMID: 21414421 DOI: 10.1016/j.meegid.2011.02.016] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Revised: 02/25/2011] [Accepted: 02/28/2011] [Indexed: 11/28/2022]
Abstract
Iron is as crucial to the pathogen as it is to the host. The tuberculosis causing bacillus, Mycobacterium tuberculosis (M.tb), is an exceptionally efficient pathogen that has evolved proficient mechanisms to sequester iron from the host despite its thick mycolate-rich outer covering and a highly impermeable membrane of phagolysosome within which it persists inside an infected host macrophage. Further, both overindulgence and moderation of iron inside a host are a threat to mycobacterial persistence. While for removing iron from the host reservoirs, mycobacteria synthesize molecules that have several times higher affinity for iron than their host counterparts, they also synthesize molecules for efficient storage of excess iron. This is supported by tightly regulated iron dependent global gene expressions. In this review we discuss the various molecules and pathways evolved by mycobacteria for an efficient iron metabolism. We also discuss the less investigated players, like iron responsive proteins and iron responsive elements in mycobacteria, and highlight the lacunae in our current understanding of iron acquisition and utilization in mycobacteria with an ultimate aim to make iron metabolism as a possible anti-mycobacterial target.
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Affiliation(s)
- Sharmistha Banerjee
- Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India
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Lawrence PK, Kittichotirat W, McDermott JE, Bumgarner RE. A three-way comparative genomic analysis of Mannheimia haemolytica isolates. BMC Genomics 2010; 11:535. [PMID: 20920355 PMCID: PMC3091684 DOI: 10.1186/1471-2164-11-535] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2010] [Accepted: 10/04/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Mannhemia haemolytica is a Gram-negative bacterium and the principal etiological agent associated with bovine respiratory disease complex. They transform from a benign commensal to a deadly pathogen, during stress such as viral infection and transportation to feedlots and cause acute pleuropneumonia commonly known as shipping fever. The U.S beef industry alone loses more than one billion dollars annually due to shipping fever. Despite its enormous economic importance there are no specific and accurate genetic markers, which will aid in understanding the pathogenesis and epidemiology of M. haemolytica at molecular level and assist in devising an effective control strategy. DESCRIPTION During our comparative genomic sequence analysis of three Mannheimia haemolytica isolates, we identified a number of genes that are unique to each strain. These genes are "high value targets" for future studies that attempt to correlate the variable gene pool with phenotype. We also identified a number of high confidence single nucleotide polymorphisms (hcSNPs) spread throughout the genome and focused on non-synonymous SNPs in known virulence genes. These SNPs will be used to design new hcSNP arrays to study variation across strains, and will potentially aid in understanding gene regulation and the mode of action of various virulence factors. CONCLUSIONS During our analysis we identified previously unknown possible type III secretion effector proteins, clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated sequences (Cas). The presence of CRISPR regions is indicative of likely co-evolution with an associated phage. If proven functional, the presence of a type III secretion system in M. haemolytica will help us re-evaluate our approach to study host-pathogen interactions. We also identified various adhesins containing immuno-dominant domains, which may interfere with host-innate immunity and which could potentially serve as effective vaccine candidates.
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Affiliation(s)
- Paulraj K Lawrence
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164-7040, USA
| | | | | | - Roger E Bumgarner
- Department of Microbiology, University of Washington, Seattle, WA 98195-7242, USA
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6
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Noto JM, Cornelissen CN. Identification of TbpA residues required for transferrin-iron utilization by Neisseria gonorrhoeae. Infect Immun 2008; 76:1960-9. [PMID: 18347046 PMCID: PMC2346694 DOI: 10.1128/iai.00020-08] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2008] [Revised: 02/15/2008] [Accepted: 03/06/2008] [Indexed: 11/20/2022] Open
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 beta-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.
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Affiliation(s)
- Jennifer M Noto
- Department of Microbiology and Immunology, Virginia Commonwealth University Medical Center, Richmond, VA 23298-0678, USA
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Stokes RH, Oakhill JS, Joannou CL, Gorringe AR, Evans RW. Meningococcal transferrin-binding proteins A and B show cooperation in their binding kinetics for human transferrin. Infect Immun 2005; 73:944-52. [PMID: 15664936 PMCID: PMC546982 DOI: 10.1128/iai.73.2.944-952.2005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neisseria meningitidis, a causative agent of bacterial meningitis and septicemia, obtains transferrin-bound iron by expressing two outer membrane-located transferrin-binding proteins, TbpA and TbpB. A novel system was developed to investigate the interaction between Tbps and human transferrin. Copurified TbpA-TbpB, recombined TbpA-TbpB, and individual TbpA and TbpB were reconstituted into liposomes and fused onto an HPA chip (BIAcore). All preparations formed stable monolayers, which, with the exception of TbpB, could be regenerated by removing bound transferrin. The ligand binding properties of these monolayers were characterized with surface plasmon resonance and shown to be specific for human transferrin. Kinetic data for diferric human transferrin binding showed that recombined TbpA-TbpB had K(a) and K(d) values similar to those of copurified TbpA-TbpB. Individual TbpA and TbpB also displayed K(a) values similar to those of copurified TbpA-TbpB, but their K(d) values were one order of magnitude higher. Chemical cross-linking studies revealed that TbpA and TbpB, in the absence of human transferrin, formed large complexes with TbpA as the predominant species. Upon human transferrin binding, a complex was formed with a molecular mass corresponding to that of a TbpB-human transferrin heterodimer as well as a higher-molecular-mass complex of this heterodimer cross-linked to TbpA. This indicates that TbpA and TbpB form a functional meningococcal receptor complex in which there is cooperativity in the human transferrin binding kinetics. However, iron loss from the diferric human transferrin-TbpA-TbpB complex was not greater than that from human transferrin alone, suggesting that additional meningococcal transport components are involved in the process of iron removal.
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Affiliation(s)
- Russell H Stokes
- Metalloprotein Research Group, Randall Division of Cell and Molecular Biophysics, GKT School of Biomedical Sciences, King's College London, Guy's Campus, New Hunt's House, London SE1 1UL, United Kingdom
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8
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Perkins-Balding D, Ratliff-Griffin M, Stojiljkovic I. Iron transport systems in Neisseria meningitidis. Microbiol Mol Biol Rev 2004; 68:154-71. [PMID: 15007100 PMCID: PMC362107 DOI: 10.1128/mmbr.68.1.154-171.2004] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Acquisition of iron and iron complexes has long been recognized as a major determinant in the pathogenesis of Neisseria meningitidis. In this review, high-affinity iron uptake systems, which allow meningococci to utilize the human host proteins transferrin, lactoferrin, hemoglobin, and haptoglobin-hemoglobin as sources of essential iron, are described. Classic features of bacterial iron transport systems, such as regulation by the iron-responsive repressor Fur and TonB-dependent transport activity, are discussed, as well as more specific features of meningococcal iron transport. Our current understanding of how N. meningitidis acquires iron from the human host and the vaccine potentials of various components of these iron transport systems are also reviewed.
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Affiliation(s)
- Donna Perkins-Balding
- Rollins Research Center, Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
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9
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Renauld-Mongénie G, Lins L, Krell T, Laffly L, Mignon M, Dupuy M, Delrue RM, Guinet-Morlot F, Brasseur R, Lissolo L. Transferrin-binding protein B of Neisseria meningitidis: sequence-based identification of the transferrin-Binding site confirmed by site-directed mutagenesis. J Bacteriol 2004; 186:850-7. [PMID: 14729713 PMCID: PMC321495 DOI: 10.1128/jb.186.3.850-857.2004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2003] [Accepted: 10/24/2003] [Indexed: 11/20/2022] Open
Abstract
A sequence-based prediction method was employed to identify three ligand-binding domains in transferrin-binding protein B (TbpB) of Neisseria meningitidis strain B16B6. Site-directed mutagenesis of residues located in these domains has led to the identification of two domains, amino acids 53 to 57 and 240 to 245, which are involved in binding to human transferrin (htf). These two domains are conserved in an alignment of different TbpB sequences from N. meningitidis and Neisseria gonorrhoeae, indicating a general functional role of the domains. Western blot analysis and BIAcore and isothermal titration calorimetry experiments demonstrated that site-directed mutations in both binding domains led to a decrease or abolition of htf binding. Analysis of mutated proteins by circular dichroism did not provide any evidence for structural alterations due to the amino acid replacements. The TbpB mutant R243N was devoid of any htf-binding activity, and antibodies elicited by the mutant showed strong bactericidal activity against the homologous strain, as well as against several heterologous tbpB isotype I strains.
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10
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Krell T, Renauld-Mongénie G, Nicolaï MC, Fraysse S, Chevalier M, Bérard Y, Oakhill J, Evans RW, Gorringe A, Lissolo L. Insight into the structure and function of the transferrin receptor from Neisseria meningitidis using microcalorimetric techniques. J Biol Chem 2003; 278:14712-22. [PMID: 12571247 DOI: 10.1074/jbc.m204461200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The transferrin receptor of Neisseria meningitidis is composed of the transmembrane protein TbpA and the outer membrane protein TbpB. Both receptor proteins have the capacity to independently bind their ligand human transferrin (htf). To elucidate the specific role of these proteins in receptor function, isothermal titration calorimetry was used to study the interaction between purified TbpA, TbpB or the entire receptor (TbpA + TbpB) with holo- and apo-htf. The entire receptor was shown to contain a single high affinity htf-binding site on TbpA and approximately two lower affinity binding sites on TbpB. The binding sites appear to be independent. Purified TbpA was shown to have strong ligand preference for apo-htf, whereas TbpA in the receptor complex with TbpB preferentially binds the holo form of htf. The orientation of the ligand specificity of TbpA toward holo-htf is proposed to be the physiological function of TbpB. Furthermore, the thermodynamic mode of htf binding by TbpB of isotypes I and II was shown to be different. A protocol for the generation of active, histidine-tagged TbpB as well as its individual N- and C-terminal domains is presented. Both domains are shown to strongly interact with each other, and isothermal titration calorimetry and circular dichroism experiments provide clear evidence for this interaction causing conformational changes. The N-terminal domain of TbpB was shown to be the site of htf binding, whereas the C-terminal domain is not involved in binding. Furthermore, the interactions between TbpA and the different domains of TbpB have been demonstrated.
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Affiliation(s)
- Tino Krell
- Aventis Pasteur, 1541 avenue Marcel Mérieux, 69280 Marcy l'Etoile, France.
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Bossé JT, Janson H, Sheehan BJ, Beddek AJ, Rycroft AN, Kroll JS, Langford PR. Actinobacillus pleuropneumoniae: pathobiology and pathogenesis of infection. Microbes Infect 2002; 4:225-35. [PMID: 11880056 DOI: 10.1016/s1286-4579(01)01534-9] [Citation(s) in RCA: 264] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Actinobacillus pleuropneumoniae causes porcine pleuropneumonia, a highly contagious disease for which there is no effective vaccine. This review considers how adhesins, iron-acquisition factors, capsule and lipopolysaccharide, RTX cytotoxins and other potential future vaccine components contribute to colonisation, to avoidance of host clearance mechanisms and to damage of host tissues.
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Affiliation(s)
- Janine T Bossé
- Molecular Infectious Diseases Group, Department of Paediatrics, Faculty of Medicine, Imperial College, St. Mary's Campus, W2 1PG, London, UK.
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12
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Bøg YS, Andresen LO, Bastholm L, Elling F, Angen O, Heegaard PM. The transferrin receptor of Actinobacillus pleuropneumoniae: quantitation of expression and structural characterization using a peptide-specific monoclonal antibody. Vet Microbiol 2001; 81:51-64. [PMID: 11356318 DOI: 10.1016/s0378-1135(01)00333-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
When Actinobacillus pleuropneumoniae (A. pp) is grown under iron-restricted conditions in vitro, transferrin binding proteins (Tbps) are induced. The functional transferrin receptor of A. pp is composed of two outer membrane proteins (Tbp1 and Tbp2) and shows an exquisite specificity for porcine transferrin. This complex was studied using a monoclonal antibody (Mab 1.48) raised against a synthetic peptide corresponding to a hydrophilic domain of Tbp2 common to several A. pp serotypes. The antibody reacted specifically with a 60-70kDa Tbp2-antigen found in all serotypes of A. pp obtained from iron-restricted culture. It was found that Tbp2 was not expressed in iron replete medium by any serotype except serotypes 5a, 5b and 6 where a weak expression was seen. There was a weak expression of related antigens in Actinobacillus indolicus and Actinobacillus suis under iron-depleted conditions while no similar antigens were detected with the Mab in iron-starved Actinobacillus lignieresii, Actinobacillus porcinus, Actinobacillus minor, Haemophilus influenzae, and Haemophilus parasuis. Using an enzyme-linked immunosorbent assay (ELISA) based on the Mab 1.48, Tbp2 could be detected in both recombinant E. coli expressing Tbp2 and in wild type A. pp grown under iron restricted conditions. The subcellular location of Tbp2 in A. pp was studied by immunoelectron microscopy using the Mab 1.48. Interestingly, all antibody binding was found inside the A. pp cells, while Tbp2 expressed in recombinant E. coli was found both in the cytosol and on the outer membrane. These results indicate that the Mab 1.48-reactive epitope of Tbp2 is surface exposed when it is expressed without Tbp1 in E. coli while the inaccessibility of this epitope of Tbp2 in A. pp could be due to shading by the association between Tbp2 and Tbp1.
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Affiliation(s)
- Y S Bøg
- Department of Biochemistry and Immunology, Danish Veterinary Laboratory, Bülowsvej 27, DK-1790, Copenhagen, Denmark.
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13
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Abstract
The ability of pathogens to obtain iron from transferrins, ferritin, hemoglobin, and other iron-containing proteins of their host is central to whether they live or die. To combat invading bacteria, animals go into an iron-withholding mode and also use a protein (Nramp1) to generate reactive oxygen species in an attempt to kill the pathogens. Some invading bacteria respond by producing specific iron chelators-siderophores-that remove the iron from the host sources. Other bacteria rely on direct contact with host iron proteins, either abstracting the iron at their surface or, as with heme, taking it up into the cytoplasm. The expression of a large number of genes (>40 in some cases) is directly controlled by the prevailing intracellular concentration of Fe(II) via its complexing to a regulatory protein (the Fur protein or equivalent). In this way, the biochemistry of the bacterial cell can accommodate the challenges from the host. Agents that interfere with bacterial iron metabolism may prove extremely valuable for chemotherapy of diseases.
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Affiliation(s)
- C Ratledge
- Department of Biological Sciences, University of Hull, Hull HU6 7RX.
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14
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Litt DJ, Palmer HM, Borriello SP. Neisseria meningitidis expressing transferrin binding proteins of Actinobacillus pleuropneumoniae can utilize porcine transferrin for growth. Infect Immun 2000; 68:550-7. [PMID: 10639416 PMCID: PMC97175 DOI: 10.1128/iai.68.2.550-557.2000] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Homologous recombination was used to generate a number of mutants of serogroup B Neisseria meningitidis B16B6 with the following characteristics: (i) an inability to bind human or porcine transferrin because of loss of both transferrin binding proteins (Tbp) A and B [strain B16B6(Str(r))/tbpA(-)B(-)] and (ii) an ability to bind porcine transferrin but not human transferrin [strain B16B6(Str(r))/tbpA(ap)B(ap)] due to replacement of the meningococcal Tbp with the Tbp of Actinobacillus pleuropneumoniae. During construction of the B16B6(Str(r))/tbpA(ap)B(ap) strain, transformants expressing only TbpA or TbpB of A. pleuropneumoniae were isolated [strains B16B6(Str(r))/tbpA(ap)B(-) and B16B6(Str(r))/tbpA(-)B(ap)]. Expression of the A. pleuropneumoniae Tbp in N. meningitidis B16B6 was iron regulated and expressed under the control of the meningococcal promoter. The relative abilities of the meningococcal transformants to bind porcine transferrin were in the order B16B6(Str(r))/tbpA(ap)B(ap) > B16B6(Str(r))/tbpA(ap)B(-) > B16B6(Str(r))/tbpA(-)B(ap). Of these transformants, only B16B6(Str(r))/tbpA(ap)B(ap) could grow in the presence of porcine transferrin as the sole iron source, achieving a growth rate similar to that of the B16B6 parent strain in the presence of human transferrin.
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Affiliation(s)
- D J Litt
- Institute of Infections and Immunity, Queen's Medical Centre, Nottingham, NG7 2UH, United Kingdom
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15
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Prinz T, Tommassen J. Association of iron-regulated outer membrane proteins of Neisseria meningitidis with the RmpM (class 4) protein. FEMS Microbiol Lett 2000; 183:49-53. [PMID: 10650201 DOI: 10.1111/j.1574-6968.2000.tb08932.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The RmpM (class 4) protein of Neisseria meningitidis has previously been shown to be associated with the outer membrane porins. In the present study, we demonstrate that this protein forms complexes with the lactoferrin receptor LbpA, the transferrin receptor TbpA and the siderophore receptor FrpB as well. This complexation apparently resulted in a stabilization of oligomeric forms of these iron-regulated proteins. In vitro experiments further revealed a reduced ability to acquire iron from human lactoferrin in the rmpM mutant. Furthermore, all TonB-dependent receptors investigated here appeared to exist as oligomers (probably dimers), suggesting that this is a general feature of this class of proteins.
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Affiliation(s)
- T Prinz
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.
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Boulton IC, Gorringe AR, Shergill JK, Joannou CL, Evans RW. A dynamic model of the meningococcal transferrin receptor. J Theor Biol 1999; 198:497-505. [PMID: 10373350 DOI: 10.1006/jtbi.1999.0928] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Iron is an essential nutrient for all organisms and consequently, the ability to bind transferrin and sequester iron from his source constitutes a distinct advantage to a blood-borne bacterial pathogen. Levels of free iron are strictly limited in human serum, largely through the action of the iron-binding protein transferrin. The acquisition of trasferrin-iron is coincident with pathogenicity among Neisseria species and a limited number of other pathogens of human and veterinary significance. In Neisseria meningitidis, transferrin binding relies on two co-expressed, outer membrane proteins distinct in aspects of both structure and function. These proteins are independently and simultaneously capable of binding human transferrin and both are required for the optimal uptake of iron from this source. It has been established that transferrin-binding proteins (designated TbpA and TbpB) form a discrete, specific complex which may be composed of a transmembrane species (composed of the TbpA dimer) associated with a single surface-exposed lipoprotein (TbpB). This more exposed protein is capable of selectively binding iron-saturated transferrin and the receptor complex has ligand-binding properties which are distinct from either of its components. Previous in vivo analyses of N. gonorrhoeae, which utilizes a closely related transferrin-iron uptake system, indicated that this receptor exists in several conformations influenced in part by the presence (or absence) of transferrin. Here we propose a dynamic model of the meningococcal transferrin receptor which is fully consistent with the current data concerning this subject. We suggest that TbpB serves as the initial binding site for iron-saturated transferrin and brings this ligand close to the associated transmembrane dimer, enabling additional binding events and orientating transferrin over the dual TbpA pores. The antagonistic association of these receptor proteins with a single ligand molecule may also induce conformational change in transferrin, thereby favouring the release of iron. As, in vivo, transferrin may have iron in one or both lobes, this dynamic molecular arrangement would enable iron uptake from either iron-binding site. In addition, the predicted molecular dimensions of the putative TbpA dimer and hTf are fully consistent with these proposals. Given the diverse data used in the formulation of this model and the consistent characteristics of transferrin binding among several significant Gram-negative pathogens, we speculate that such receptor-ligand interactions may be, at least in part, conserved between species. Consequently, this model may be applicable to bacteria other than N. meningitidis.
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Affiliation(s)
- I C Boulton
- Centre for Applied Microbiology and Research, Salisbury, SP4 0JG, UK.
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Renauld-Mongénie G, Latour M, Poncet D, Naville S, Quentin-Millet MJ. Both the full-length and the N-terminal domain of the meningococcal transferrin-binding protein B discriminate between human iron-loaded and apo-transferrin. FEMS Microbiol Lett 1998; 169:171-7. [PMID: 9851049 DOI: 10.1111/j.1574-6968.1998.tb13314.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
We have readdressed the ability of the transferrin-binding protein B (TbpB) from Neisseria meningitidis to discriminate between the iron-loaded and the iron-free human transferrin (hTf) by using the BIAcore technology, a powerful experimental technique for the observation of direct interactions between a receptor and its ligands, without the use of labels. Recombinant full-length TbpB from five N. meningitidis strains were produced and purified from Escherichia coli as fusion proteins. They showed a preference for the binding to iron-loaded hTf. As for the full-length molecule, we have demonstrated that the minimal N-terminal hTf binding domain of meningococcal TbpB from B16B6 and M982 strains was able to discriminate between both hTf forms.
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