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Nader M, Journet L, Meksem A, Guillon L, Schalk IJ. Mechanism of Ferripyoverdine Uptake by Pseudomonas aeruginosa Outer Membrane Transporter FpvA: No Diffusion Channel Formed at Any Time during Ferrisiderophore Uptake. Biochemistry 2011; 50:2530-40. [DOI: 10.1021/bi101821n] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mirella Nader
- UMR7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brandt, F-67513 Illkirch, France
| | - Laure Journet
- UMR7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brandt, F-67513 Illkirch, France
| | - Ahmed Meksem
- UMR7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brandt, F-67513 Illkirch, France
| | - Laurent Guillon
- UMR7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brandt, F-67513 Illkirch, France
| | - Isabelle J. Schalk
- UMR7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brandt, F-67513 Illkirch, France
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The fbpABC operon is required for Ton-independent utilization of xenosiderophores by Neisseria gonorrhoeae strain FA19. Infect Immun 2010; 79:267-78. [PMID: 21041493 DOI: 10.1128/iai.00807-10] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neisseria gonorrhoeae produces no known siderophores but can employ host-derived, iron-binding proteins, including transferrin and lactoferrin, as iron sources. Given the propensity of this pathogen to hijack rather than synthesize iron-sequestering molecules, we hypothesized that the ability to use siderophores produced by other bacteria, or xenosiderophores, may also play a role in the survival of the gonococcus. Among a panel of diverse siderophores, only the catecholate xenosiderophores enterobactin and salmochelin promoted growth of gonococcal strain FA19. Surprisingly, the internalization pathway was independent of TonB or any of the TonB-dependent transporters. Xenosiderophore-mediated growth was similarly independent of the pilin-extruding secretin formed by PilQ and of the hydrophobic-agent efflux system composed of MtrCDE. The fbpABC operon encodes a periplasmic-binding-protein-dependent ABC transport system that enables the gonococcus to transport iron into the cell subsequent to outer membrane translocation. We hypothesized that the FbpABC proteins, required for ferric iron transport from transferrin and lactoferrin, might also contribute to the utilization of xenosiderophores as iron sources. We created mutants that conditionally expressed FbpABC from an IPTG-inducible promoter. We determined that expression of FbpABC was required for growth of gonococcal strain FA19 in the presence of enterobactin and salmochelin. The monomeric component of enterobactin, dihydroxybenzoylserine (DHBS), and the S2 form of salmochelin specifically promoted FbpABC-dependent growth of FA19. This study demonstrated that the gonococcal FbpABC transport system is required for utilization of some xenosiderophores as iron sources and that growth promotion by these ferric siderophores can occur in the absence of TonB or individual TonB-dependent transporters.
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Abstract
Colicin B is a 55 kDa dumbbell-shaped protein toxin that uses the TonB system (outer membrane transporter, FepA, and three cytoplasmic membrane proteins TonB/ExbB/ExbD) to enter and kill Escherichia coli. FepA is a 22-stranded beta-barrel with its lumen filled by an amino-terminal globular domain containing an N-terminal semiconserved region, known as the TonB box, to which TonB binds. To investigate the mechanism of colicin B translocation across the outer membrane, we engineered cysteine (Cys) substitutions in the globular domain of FepA. Colicin B caused increased exposure to biotin maleimide labelling of all Cys substitutions, but to different degrees, with TonB as well as the FepA TonB box required for all increases. Because of the large increases in exposure for Cys residues from T13 to T51, we conclude that colicin B is translocated through the lumen of FepA, rather than along the lipid-barrel interface or through another protein. Part of the FepA globular domain (residues V91-V142) proved relatively refractory to labelling, indicating either that the relevant Cys residues were sequestered by an unknown protein or that a significant portion of the FepA globular domain remained inside the barrel, requiring concomitant conformational rearrangement of colicin B during its translocation. Unexpectedly, TonB was also required for colicin-induced exposure of the FepA TonB box, suggesting that TonB binds FepA at a different site prior to interaction with the TonB box.
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López CS, Alice AF, Chakraborty R, Crosa JH. Identification of amino acid residues required for ferric-anguibactin transport in the outer-membrane receptor FatA of Vibrio anguillarum. MICROBIOLOGY-SGM 2007; 153:570-584. [PMID: 17259629 DOI: 10.1099/mic.0.2006/001735-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Vibrio anguillarum 775 is a fish pathogen that causes a disease characterized by a fatal haemorrhagic septicaemia. It harbours the 65 kbp pJM1 plasmid, which encodes an iron sequestering system specific for the siderophore anguibactin and is essential for virulence. The genes involved in the biosynthesis of anguibactin are located on both the pJM1 plasmid and the chromosome. However, the genes for the outer-membrane receptor FatA and the other transport proteins are only carried on the plasmid. With the aim of elucidating the mechanism of ferric-anguibactin transport mediated by FatA, this work focuses on the identification of FatA amino acid residues that play a role in the transport of ferric-anguibactin, by analysing the transport kinetics of site-directed mutants. The mutations studied were located in conserved residues of the lock region, which contains a cluster of ten residues belonging to the N-terminal and barrel domains, and of the channel region of FatA, which contains conserved glycines located in the beta5-beta6 loop and a conserved arginine located in strand 11 of the beta-barrel. In the case of the FatA lock region, it is clear that although the residues analysed in this work (R95, K130, E505 and E550) are conserved among various outer-membrane receptors, their involvement in the transport process might differ among receptors. Furthermore, it was determined that in the FatA channel region double substitutions of the conserved glycines 131 and 143 with alanine resulted in a variant receptor unable to transport ferric-anguibactin. It was also shown that the conserved arginine 428 located in strand 11 is essential for transport. The results suggest that a conformational change or partial unfolding of the plug domain occurs during ferric-anguibactin transport.
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Affiliation(s)
- Claudia S López
- Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, OR 97239, USA
| | - Alejandro F Alice
- Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, OR 97239, USA
| | - Ranjan Chakraborty
- Department of Health Sciences, College of Public and Allied Health, East Tennessee State University, Johnson City, TN, USA
| | - Jorge H Crosa
- Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, OR 97239, USA
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López CS, Crosa JH. Characterization of ferric-anguibactin transport in Vibrio anguillarum. Biometals 2007; 20:393-403. [PMID: 17287889 DOI: 10.1007/s10534-007-9084-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2007] [Accepted: 01/15/2007] [Indexed: 10/23/2022]
Abstract
The fish pathogen Vibrio anguillarum is the causative agent of a fatal hemorrhagic septicemia in salmonid fish. Many serotype O1 strains harbors a 65 Kbp plasmid (pJM1 encoding an iron sequestering system essential for virulence. The genes involved in the biosynthesis of the indigenous siderophore anguibactin are encoded by both the pJM1 plasmid and the chromosome, while those involved in the transport of the ferric-siderophore complex, including the outer membrane receptor, are plasmid-encoded. This work describes the role of specific amino acid residues of the outer membrane receptor FatA in the mechanism of transport of ferric-anguibactin. FatA modeling indicated that this protein has a 22 stranded beta-barrel blocked by the plug domain, the latter being formed by residues 51-154. Deletion of the plug domain resulted in a receptor unable to act as an open channel for the transport of the ferric anguibactin complex.
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Affiliation(s)
- Claudia S López
- Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, OR 97239, USA
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Chakraborty R, Storey E, van der Helm D. Molecular mechanism of ferricsiderophore passage through the outer membrane receptor proteins of Escherichia coli. Biometals 2006; 20:263-74. [PMID: 17186377 DOI: 10.1007/s10534-006-9060-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2006] [Accepted: 11/28/2006] [Indexed: 10/23/2022]
Abstract
Iron is an essential nutrient for all microorganisms with a few exceptions. Microorganisms use a variety of systems to acquire iron from the surrounding environment. One such system includes production of an organic molecule known as a siderophore by many bacteria and fungi. Siderophores have the capacity to specifically chelate ferric ions. The ferricsiderophore complex is then transported into the cell via a specific receptor protein located in the outer membrane. This is an energy dependent process and is the subject of investigation in many research laboratories. The crystal structures of three outer membrane ferricsiderophore receptor proteins FepA, FhuA and FecA from Escherichia coli and two FpvA and FptA from Pseudomonas aeruginosa have recently been solved. Four of them, FhuA, FecA, FpvA and FptA have been solved in ligand-bound forms, which gave insight into the residues involved in ligand binding. The structures are similar and show the presence of similar domains; for example, all of them consist of a 22 strand-beta-barrel formed by approximately 600 C-terminal residues while approximately 150 N-terminal residues fold inside the barrel to form a plug domain. The plug domain obstructs the passage through the barrel; therefore our research focuses on the mechanism through which the ferricsiderophore complex is transported across the receptor into the periplasm. There are two possibilities, one in which the plug domain is expelled into the periplasm making way for the ferricsiderophore complex and the second in which the plug domain undergoes structural rearrangement to form a channel through which the complex slides into the periplasm. Multiple alignment studies involving protein sequences of a large number of outer membrane receptor proteins that transport ferricsiderophores have identified several conserved residues. All of the conserved residues are located within the plug and barrel domain below the ligand binding site. We have substituted a number of these residues in FepA and FhuA with either alanine or glutamine resulting in substantial changes in the chemical properties of the residues. This was done to study the effect of the substitutions on the transport of ferricsiderophores. Another strategy used was to create a disulfide bond between the residues located on two adjacent beta-strands of the plug domain or between the residues of the plug domain and the beta-barrel in FhuA by substituting appropriate residues with cysteine. We have looked for the variants where the transport is affected without altering the binding. The data suggest a distinct role of these residues in the mechanism of transport. Our data also indicate that these transporters share a common mechanism of transport and that the plug remains within the barrel and possibly undergoes rearrangement to form a channel to transport the ferricsiderophore from the binding site to the periplasm.
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Affiliation(s)
- Ranjan Chakraborty
- Department of Health Sciences, College of Public and Allied Health, East Tennessee State University, Johnson City, TN 37614, USA.
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Ling JML, Schryvers AB. Perspectives on interactions between lactoferrin and bacteriaThis paper is one of a selection of papers published in this Special Issue, entitled 7th International Conference on Lactoferrin: Structure, Function, and Applications, and has undergone the Journal's usual peer review process. Biochem Cell Biol 2006; 84:275-81. [PMID: 16936797 DOI: 10.1139/o06-044] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Lactoferrin has long been recognized for its antimicrobial properties, initially attributed primarily to iron sequestration. It has since become apparent that interaction between the host and bacteria is modulated by a complex series of interactions between lactoferrin and bacteria, lactoferrin and bacterial products, and lactoferrin and host cells. The primary focus of this review is the interaction between lactoferrin and bacteria, but interactions with the lactoferrin-derived cationic peptide lactoferricin will also be discussed. We will summarize what is currently known about the interaction between lactoferrin (or lactoferricin) and surface or secreted bacterial components, comment on the potential physiological relevance of the findings, and identify key questions that remain unanswered.
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Affiliation(s)
- Jessmi M L Ling
- Department of Microbiology and Infectious Diseases, 274 Heritage Medical Research Building, Faculty of Medicine, University of Calgary, 3330 Hospital Dr. N.W, Calgary, AB T2N 4N1, Canada
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Perkins-Balding D, Baer MT, Stojiljkovic I. Identification of functionally important regions of a haemoglobin receptor from Neisseria meningitidis. MICROBIOLOGY-SGM 2004; 149:3423-3435. [PMID: 14663076 DOI: 10.1099/mic.0.26448-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The HmbR outer-membrane receptor enables Neisseria meningitidis to use haemoglobin (Hb) as a source of iron. This protein functions by binding Hb, removing haem from it, and releasing the haem into the periplasm. Functionally important HmbR receptor domains were discerned using a series of HmbR deletions and site-directed mutations. Mutations exhibiting similar defective phenotypes in N. meningitidis fell into two groups. The first group of mutations affected Hb binding and were located in putative extracellular loops (L) L2 (amino acid residues (aa) 192-230) and L3 (aa 254-284). The second group of mutations resulted in a failure to utilize Hb but proficiency in Hb binding was retained. These mutations localized to the putative extracellular loops L6 (aa 420-462) and L7 (aa 486-516). A highly conserved protein motif found in all haem/Hb receptors, within putative extracellular loop L7 of HmbR, is essential for Hb utilization but not required for Hb binding. This finding suggests a mechanistic involvement of this motif in haem removal from Hb. In addition, an amino-terminal deletion in the putative cork-like domain of HmbR affected Hb usage but not Hb binding. This result supports a role of the cork domain in utilization steps that are subsequent to Hb binding.
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Affiliation(s)
- D Perkins-Balding
- Department of Microbiology and Immunology, Emory School of Medicine, 1510 Clifton Rd, Atlanta, GA 30322, USA
| | - M T Baer
- Department of Microbiology and Immunology, Emory School of Medicine, 1510 Clifton Rd, Atlanta, GA 30322, USA
| | - I Stojiljkovic
- Department of Microbiology and Immunology, Emory School of Medicine, 1510 Clifton Rd, Atlanta, GA 30322, USA
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