1
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Badve P, Meier KK. Defining Requirements for Heme Binding in PGRMC1 and Identifying Key Elements that Influence Protein Dimerization. Biochemistry 2024; 63:926-938. [PMID: 38489495 DOI: 10.1021/acs.biochem.3c00718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/17/2024]
Abstract
Progesterone receptor membrane component 1 (PGRMC1) binds heme via a surface-exposed site and displays some structural resemblance to cytochrome b5 despite their different functions. In the case of PGRMC1, it is the protein interaction with drug-metabolizing cytochrome P450s and the epidermal growth factor receptor that has garnered the most attention. These interactions are thought to result in a compromised ability to metabolize common chemotherapy agents and to enhance cancer cell proliferation. X-ray crystallography and immunoprecipitation data have suggested that heme-mediated PGRMC1 dimers are important for facilitating these interactions. However, more recent studies have called into question the requirement of heme binding for PGRMC1 dimerization. Our study employs spectroscopic and computational methods to probe and define heme binding and its impact on PGRMC1 dimerization. Fluorescence, electron paramagnetic resonance and circular dichroism spectroscopies confirm heme binding to apo-PGRMC1 and were used to demonstrate the stabilizing effect of heme on the wild-type protein. We also utilized variants (C129S and Y113F) to precisely define the contributions of disulfide bonds and direct heme coordination to PGRMC1 dimerization. Understanding the key factors involved in these processes has important implications for downstream protein-protein interactions that may influence the metabolism of chemotherapeutic agents. This work opens avenues for deeper exploration into the physiological significance of the truncated-PGRMC1 model and developing design principles for potential therapeutics to target PGRMC1 dimerization and downstream interactions.
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Affiliation(s)
- Prajakta Badve
- Department of Chemistry, University of Miami, Coral Gables, Florida 33146, United States
| | - Katlyn K Meier
- Department of Chemistry, University of Miami, Coral Gables, Florida 33146, United States
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2
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Brangulis K, Akopjana I, Bogans J, Kazaks A, Tars K. Structural studies of chromosomally encoded outer surface lipoprotein BB0158 from Borrelia burgdorferi sensu stricto. Ticks Tick Borne Dis 2024; 15:102287. [PMID: 38016210 DOI: 10.1016/j.ttbdis.2023.102287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2023] [Revised: 11/21/2023] [Accepted: 11/22/2023] [Indexed: 11/30/2023]
Abstract
Lyme disease, or also known as Lyme borreliosis, is caused by the spirochetes belonging to the Borrelia burgdorferi sensu lato complex, which can enter the human body following the bite of an infected tick. Many membrane lipid-bound proteins, also known as lipoproteins, are located on the surface of B. burgdorferi sensu lato and play a crucial role in the spirochete to interact with its environment, whether in ticks or mammals. Since the spirochete needs to perform various tasks, such as resisting the host's immune system or spreading throughout the organism, it is not surprising that numerous surface proteins have been found to be essential for B. burgdorferi sensu lato complex bacteria in causing Lyme disease. In this study, we have determined (at 2.4 Å resolution) and characterized the 3D structure of BB0158, one of the few chromosomally encoded outer surface proteins from B. burgdorferi sensu stricto. BB0158 belongs to the paralogous gene family 44 (PFam44), consisting of four other members (BB0159, BBA04, BBE09 and BBK52). The characterization of BB0158, which appears to form a domain-swapped dimer, in conjunction with the characterization of the corresponding PFam44 members, certainly contribute to our understanding of B. burgdorferi sensu stricto proteins.
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Affiliation(s)
- Kalvis Brangulis
- Latvian Biomedical Research and Study Centre, Ratsupites 1 k-1, Riga LV-1067, Latvia.
| | - Inara Akopjana
- Latvian Biomedical Research and Study Centre, Ratsupites 1 k-1, Riga LV-1067, Latvia
| | - Janis Bogans
- Latvian Biomedical Research and Study Centre, Ratsupites 1 k-1, Riga LV-1067, Latvia
| | - Andris Kazaks
- Latvian Biomedical Research and Study Centre, Ratsupites 1 k-1, Riga LV-1067, Latvia
| | - Kaspars Tars
- Latvian Biomedical Research and Study Centre, Ratsupites 1 k-1, Riga LV-1067, Latvia
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3
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Mahoney BJ, Goring AK, Wang Y, Dasika P, Zhou A, Grossbard E, Cascio D, Loo JA, Clubb RT. Development and atomic structure of a new fluorescence-based sensor to probe heme transfer in bacterial pathogens. J Inorg Biochem 2023; 249:112368. [PMID: 37729854 DOI: 10.1016/j.jinorgbio.2023.112368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Revised: 08/11/2023] [Accepted: 09/07/2023] [Indexed: 09/22/2023]
Abstract
Heme is the most abundant source of iron in the human body and is actively scavenged by bacterial pathogens during infections. Corynebacterium diphtheriae and other species of actinobacteria scavenge heme using cell wall associated and secreted proteins that contain Conserved Region (CR) domains. Here we report the development of a fluorescent sensor to measure heme transfer from the C-terminal CR domain within the HtaA protein (CR2) to other hemoproteins within the heme-uptake system. The sensor contains the CR2 domain inserted into the β2 to β3 turn of the Enhanced Green Fluorescent Protein (EGFP). A 2.45 Å crystal structure reveals the basis of heme binding to the CR2 domain via iron-tyrosyl coordination and shares conserved structural features with CR domains present in Corynebacterium glutamicum. The structure and small angle X-ray scattering experiments are consistent with the sensor adopting a V-shaped structure that exhibits only small fluctuations in inter-domain positioning. We demonstrate heme transfer from the sensor to the CR domains located within the HtaA or HtaB proteins in the heme-uptake system as measured by a ∼ 60% increase in sensor fluorescence and native mass spectrometry.
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Affiliation(s)
- Brendan J Mahoney
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 611 Charles E. Young Drive East, Los Angeles, CA 90095, USA; UCLA-DOE Institute of Genomics and Proteomics, University of California, Los Angeles, 611 Charles E. Young Drive East, Los Angeles, CA 90095, USA
| | - Andrew K Goring
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 611 Charles E. Young Drive East, Los Angeles, CA 90095, USA
| | - Yueying Wang
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 611 Charles E. Young Drive East, Los Angeles, CA 90095, USA
| | - Poojita Dasika
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 611 Charles E. Young Drive East, Los Angeles, CA 90095, USA
| | - Anqi Zhou
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 611 Charles E. Young Drive East, Los Angeles, CA 90095, USA
| | - Emmitt Grossbard
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 611 Charles E. Young Drive East, Los Angeles, CA 90095, USA
| | - Duilio Cascio
- UCLA-DOE Institute of Genomics and Proteomics, University of California, Los Angeles, 611 Charles E. Young Drive East, Los Angeles, CA 90095, USA
| | - Joseph A Loo
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 611 Charles E. Young Drive East, Los Angeles, CA 90095, USA; UCLA-DOE Institute of Genomics and Proteomics, University of California, Los Angeles, 611 Charles E. Young Drive East, Los Angeles, CA 90095, USA; Molecular Biology Institute, University of California, Los Angeles, 611 Charles E. Young Drive East, Los Angeles, CA 90095, USA
| | - Robert T Clubb
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 611 Charles E. Young Drive East, Los Angeles, CA 90095, USA; UCLA-DOE Institute of Genomics and Proteomics, University of California, Los Angeles, 611 Charles E. Young Drive East, Los Angeles, CA 90095, USA; Molecular Biology Institute, University of California, Los Angeles, 611 Charles E. Young Drive East, Los Angeles, CA 90095, USA.
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4
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Extracellular haem utilization by the opportunistic pathogen Pseudomonas aeruginosa and its role in virulence and pathogenesis. Adv Microb Physiol 2021; 79:89-132. [PMID: 34836613 DOI: 10.1016/bs.ampbs.2021.07.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Iron is an essential micronutrient for all bacteria but presents a significant challenge given its limited bioavailability. Furthermore, iron's toxicity combined with the need to maintain iron levels within a narrow physiological range requires integrated systems to sense, regulate and transport a variety of iron complexes. Most bacteria encode systems to chelate and transport ferric iron (Fe3+) via siderophore receptor mediated uptake or via cytoplasmic energy dependent transport systems. Pathogenic bacteria have further lowered the barrier to iron acquisition by employing systems to utilize haem as a source of iron. Haem, a lipophilic and toxic molecule, presents a significant challenge for transport into the cell. As such pathogenic bacteria have evolved sophisticated cell surface signaling (CSS) and transport systems to sense and obtain haem from the host. Once internalized haem is cleaved by both oxidative and non-oxidative mechanisms to release iron. Herein we summarize our current understanding of the mechanism of haem sensing, uptake and utilization in Pseudomonas aeruginosa, its role in pathogenesis and virulence, and the potential of these systems as antimicrobial targets.
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5
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Dent AT, Brimberry M, Albert T, Lanzilotta WN, Moënne-Loccoz P, Wilks A. Axial Heme Coordination by the Tyr-His Motif in the Extracellular Hemophore HasAp Is Critical for the Release of Heme to the HasR Receptor of Pseudomonas aeruginosa. Biochemistry 2021; 60:2549-2559. [PMID: 34324310 DOI: 10.1021/acs.biochem.1c00389] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Pseudomonas aeruginosa senses extracellular heme via an extra cytoplasmic function σ factor that is activated upon interaction of the hemophore holo-HasAp with the HasR receptor. Herein, we show Y75H holo-HasAp interacts with HasR but is unable to release heme for signaling and uptake. To understand this inhibition, we undertook a spectroscopic characterization of Y75H holo-HasAp by resonance Raman (RR), electron paramagnetic resonance (EPR), and X-ray crystallography. The RR spectra are consistent with a mixed six-coordinate high-spin (6cHS), six-coordinate low-spin (6cLS) heme configuration and an H218O exchangeable FeIII-O stretching frequency with 16O/18O and H/D isotope shifts that support a two-body Fe-OH2 oscillator with (iron-hydroxy)-like character as both hydrogen atoms are engaged in short hydrogen bond interactions with protein side chains. Further support comes from the EPR spectrum of Y75H holo-HasAp that shows a LS rhombic signal with ligand-field splitting values intermediate between those of His-hydroxy and bis-His ferric hemes. The crystal structure of Y75H holo-HasAp confirmed the coordinated solvent molecule hydrogen bonded through H75 and H83. The long-range conformational rearrangement of HasAp upon heme binding can still take place in Y75H holo-HasAp, because the intercalation of a hydroxy ligand between the heme iron and H75 allows the variant to reproduce the heme binding pocket observed in wild-type holo-HasAp. However, in the absence of a covalent linkage to the Y75 loop combined with the malleability provided by the bracketing H75 and H83 hydrogen bonds, either the hydroxy sixth ligand remains bound after complexation of Y75H holo-HasAp with HasR or rearrangement and coordination of H85 prevent heme transfer.
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Affiliation(s)
- Alecia T Dent
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, 20 Penn Street, Baltimore, Maryland 21201, United States
| | - Marley Brimberry
- Department of Biochemistry and Molecular Biology, Franklin College of Arts and Sciences, University of Georgia, Athens, Georgia 30602, United States
| | - Therese Albert
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, Portland, Oregon 97239, United States
| | - William N Lanzilotta
- Department of Biochemistry and Molecular Biology, Franklin College of Arts and Sciences, University of Georgia, Athens, Georgia 30602, United States
| | - Pierre Moënne-Loccoz
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, Portland, Oregon 97239, United States
| | - Angela Wilks
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, 20 Penn Street, Baltimore, Maryland 21201, United States
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6
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Ellis-Guardiola K, Mahoney BJ, Clubb RT. NEAr Transporter (NEAT) Domains: Unique Surface Displayed Heme Chaperones That Enable Gram-Positive Bacteria to Capture Heme-Iron From Hemoglobin. Front Microbiol 2021; 11:607679. [PMID: 33488548 PMCID: PMC7815599 DOI: 10.3389/fmicb.2020.607679] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 12/03/2020] [Indexed: 11/13/2022] Open
Abstract
Iron is an important micronutrient that is required by bacteria to proliferate and to cause disease. Many bacterial pathogens forage iron from human hemoglobin (Hb) during infections, which contains this metal within heme (iron-protoporphyrin IX). Several clinically important pathogenic species within the Firmicutes phylum scavenge heme using surface-displayed or secreted NEAr Transporter (NEAT) domains. In this review, we discuss how these versatile proteins function in the Staphylococcus aureus Iron-regulated surface determinant system that scavenges heme-iron from Hb. S. aureus NEAT domains function as either Hb receptors or as heme-binding chaperones. In vitro studies have shown that heme-binding NEAT domains can rapidly exchange heme amongst one another via transiently forming transfer complexes, leading to the interesting hypothesis that they may form a protein-wire within the peptidoglycan layer through which heme flows from the microbial surface to the membrane. In Hb receptors, recent studies have revealed how dedicated heme- and Hb-binding NEAT domains function synergistically to extract Hb's heme molecules, and how receptor binding to the Hb-haptoglobin complex may block its clearance by macrophages, prolonging microbial access to Hb's iron. The functions of NEAT domains in other Gram-positive bacteria are also reviewed.
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Affiliation(s)
- Ken Ellis-Guardiola
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, United States
- UCLA-DOE Institute for Genomics and Proteomics, University of California, Los Angeles, Los Angeles, CA, United States
| | - Brendan J. Mahoney
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, United States
- UCLA-DOE Institute for Genomics and Proteomics, University of California, Los Angeles, Los Angeles, CA, United States
| | - Robert T. Clubb
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, United States
- UCLA-DOE Institute for Genomics and Proteomics, University of California, Los Angeles, Los Angeles, CA, United States
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA, United States
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7
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Conroy BS, Grigg JC, Kolesnikov M, Morales LD, Murphy MEP. Staphylococcus aureus heme and siderophore-iron acquisition pathways. Biometals 2019; 32:409-424. [PMID: 30911924 DOI: 10.1007/s10534-019-00188-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 03/18/2019] [Indexed: 11/24/2022]
Abstract
Staphylococcus aureus is a versatile opportunistic human pathogen. Infection by this bacterium requires uptake of iron from the human host, but iron is highly restricted in this environment. Staphylococcus aureus iron sufficiency is achieved primarily through uptake of heme and high-affinity iron chelators, known as siderophores. Two siderophores (staphyloferrins) are produced and secreted by S. aureus into the extracellular environment to capture iron. Staphylococcus aureus expresses specific uptake systems for staphyloferrins and more general uptake systems for siderophores produced by other microorganisms. The S. aureus heme uptake system uses highly-specific cell surface receptors to extract heme from hemoglobin and hemoglobin-haptoglobin complexes for transport into the cytoplasm where it is degraded to liberate iron. Initially thought to be independent systems, recent findings indicate that these iron uptake pathways intersect. IruO is a reductase that releases iron from heme and some ferric-siderophores. Moreover, multifunctional SbnI produces a precursor for staphyloferrin B biosynthesis, and also binds heme to regulate expression of the staphyloferrin B biosynthesis pathway. Intersection of the S. aureus iron uptake pathways is hypothesized to be important for rapid adaptation to available iron sources. Components of the heme and siderophore uptake systems are currently being targeted in the development of therapeutics against S. aureus.
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Affiliation(s)
- Brigid S Conroy
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, V6T 1Z3, Canada
| | - Jason C Grigg
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, V6T 1Z3, Canada
| | - Maxim Kolesnikov
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, V6T 1Z3, Canada
| | - L Daniela Morales
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, V6T 1Z3, Canada
| | - Michael E P Murphy
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, V6T 1Z3, Canada.
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8
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Dent AT, Mouriño S, Huang W, Wilks A. Post-transcriptional regulation of the Pseudomonas aeruginosa heme assimilation system (Has) fine-tunes extracellular heme sensing. J Biol Chem 2018; 294:2771-2785. [PMID: 30593511 DOI: 10.1074/jbc.ra118.006185] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 12/27/2018] [Indexed: 01/23/2023] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that utilizes heme as a primary iron source within the host. Extracellular heme is sensed via a heme assimilation system (has) that encodes an extracytoplasmic function (ECF) σ factor system. Herein, using has deletion mutants, quantitative PCR analyses, and immunoblotting, we show that the activation of the σ factor HasI requires heme release from the hemophore HasAp to the outer-membrane receptor HasR. Using RT-PCR and 5'-RACE, we observed that following transcriptional activation of the co-transcribed hasRAp, it is further processed into specific mRNAs varying in stability. We noted that the processing and variation in stability of the hasAp and hasR mRNAs in response to heme provide a mechanism for differential expression from co-transcribed genes. The multiple layers of post-transcriptional regulation of the ECF signaling cascade, including the previously reported post-transcriptional regulation of HasAp by the heme metabolites biliverdin IXβ and IXδ, allow fine-tuning of the cell-surface signaling system in response to extracellular heme levels. We hypothesize that the complex post-transcriptional regulation of the Has system provides P. aeruginosa an advantage in colonizing a variety of physiological niches in the host.
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Affiliation(s)
- Alecia T Dent
- From the Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201
| | - Susana Mouriño
- From the Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201
| | - Weiliang Huang
- From the Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201
| | - Angela Wilks
- From the Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201
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9
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Misra N, Wines TF, Knopp CL, McGuire MA, Tinker JK. Expression, immunogenicity and variation of iron-regulated surface protein A from bovine isolates of Staphylococcus aureus. FEMS Microbiol Lett 2017; 364:3739792. [PMID: 28430959 DOI: 10.1093/femsle/fnx082] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Accepted: 04/18/2017] [Indexed: 01/24/2023] Open
Abstract
Staphylococcus aureus iron-regulated surface protein A (IsdA) is a fibrinogen and fibronectin adhesin that also contributes to iron sequestration and resistance to innate immunity. IsdA is conserved in human isolates and has been investigated as a human vaccine candidate. Here we report the expression of isdA, the efficacy of anti-IsdA responses and the existence of IsdA sequence variants from bovine Staphylococcus. Clinical staphylococci were obtained from US dairy farms and assayed by PCR for the presence and expression of isdA. isdA-positive species from bovines included S. aureus, S. haemolyticus and S. chromogenes. Immunoassays on bovine milk and serum confirmed the induction and opsonophagocytic activity of anti-IsdA humoral responses. The variable region of isdA was sequenced and protein alignments predicted the presence of two main variants consistent with those from human S. aureus. Mouse antibodies against one IsdA variant reduced staphylococcal binding to fibronectin in vitro in an isotype-dependent manner. Purified IsdA variants bound distinctly to fibronectin and fibrinogen. Our findings demonstrate that variability within the C-terminus of this adhesin affects immune reactivity and binding specificity, but are consistent with the significance of IsdA in bovine disease and relevant for vaccine development.
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Affiliation(s)
- Neha Misra
- Biomolecular Ph.D. Program, Boise State University, Boise, ID 83725, USA
| | - Tyler F Wines
- Department of Biological Sciences, Boise State University, Boise, ID 83725, USA
| | - Colton L Knopp
- Department of Biological Sciences, Boise State University, Boise, ID 83725, USA
| | - Mark A McGuire
- Department of Animal and Veterinary Science, University of Idaho, Moscow, ID 83844, USA
| | - Juliette K Tinker
- Biomolecular Ph.D. Program, Boise State University, Boise, ID 83725, USA.,Department of Biological Sciences, Boise State University, Boise, ID 83725, USA
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10
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Naoe Y, Nakamura N, Rahman MM, Tosha T, Nagatoishi S, Tsumoto K, Shiro Y, Sugimoto H. Structural basis for binding and transfer of heme in bacterial heme-acquisition systems. Proteins 2017; 85:2217-2230. [PMID: 28913898 DOI: 10.1002/prot.25386] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2017] [Revised: 08/21/2017] [Accepted: 09/11/2017] [Indexed: 01/10/2023]
Abstract
Periplasmic heme-binding proteins (PBPs) in Gram-negative bacteria are components of the heme acquisition system. These proteins shuttle heme across the periplasmic space from outer membrane receptors to ATP-binding cassette (ABC) heme importers located in the inner-membrane. In the present study, we characterized the structures of PBPs found in the pathogen Burkholderia cenocepacia (BhuT) and in the thermophile Roseiflexus sp. RS-1 (RhuT) in the heme-free and heme-bound forms. The conserved motif, in which a well-conserved Tyr interacts with the nearby Arg coordinates on heme iron, was observed in both PBPs. The heme was recognized by its surroundings in a variety of manners including hydrophobic interactions and hydrogen bonds, which was confirmed by isothermal titration calorimetry. Furthermore, this study of 3 forms of BhuT allowed the first structural comparison and showed that the heme-binding cleft of BhuT adopts an "open" state in the heme-free and 2-heme-bound forms, and a "closed" state in the one-heme-bound form with unique conformational changes. Such a conformational change might adjust the interaction of the heme(s) with the residues in PBP and facilitate the transfer of the heme into the translocation channel of the importer.
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Affiliation(s)
- Youichi Naoe
- Biometal Science Laboratory, RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo, 679-5148, Japan
| | - Nozomi Nakamura
- Biometal Science Laboratory, RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo, 679-5148, Japan.,Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori, Ako, Hyogo, 678-1297, Japan
| | - Md Mahfuzur Rahman
- Biometal Science Laboratory, RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo, 679-5148, Japan.,Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori, Ako, Hyogo, 678-1297, Japan
| | - Takehiko Tosha
- Biometal Science Laboratory, RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo, 679-5148, Japan
| | - Satoru Nagatoishi
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-8656, Japan
| | - Kouhei Tsumoto
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-8656, Japan.,Laboratory of Medical Proteomics, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo, 108-8639, Japan
| | - Yoshitsugu Shiro
- Biometal Science Laboratory, RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo, 679-5148, Japan.,Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori, Ako, Hyogo, 678-1297, Japan
| | - Hiroshi Sugimoto
- Biometal Science Laboratory, RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo, 679-5148, Japan.,Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori, Ako, Hyogo, 678-1297, Japan
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11
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Abstract
Iron is an essential micronutrient for both microbes and humans alike. For well over half a century we have known that this element, in particular, plays a pivotal role in health and disease and, most especially, in shaping host-pathogen interactions. Intracellular iron concentrations serve as a critical signal in regulating the expression not only of high-affinity iron acquisition systems in bacteria, but also of toxins and other noted virulence factors produced by some major human pathogens. While we now are aware of many strategies that the host has devised to sequester iron from invading microbes, there are as many if not more sophisticated mechanisms by which successful pathogens overcome nutritional immunity imposed by the host. This review discusses some of the essential components of iron sequestration and scavenging mechanisms of the host, as well as representative Gram-negative and Gram-positive pathogens, and highlights recent advances in the field. Last, we address how the iron acquisition strategies of pathogenic bacteria may be exploited for the development of novel prophylactics or antimicrobials.
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12
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Abstract
Iron is essential for the survival of most bacteria but presents a significant challenge given its limited bioavailability. Furthermore, the toxicity of iron combined with the need to maintain physiological iron levels within a narrow concentration range requires sophisticated systems to sense, regulate, and transport iron. Most bacteria have evolved mechanisms to chelate and transport ferric iron (Fe3+) via siderophore receptor systems, and pathogenic bacteria have further lowered this barrier by employing mechanisms to utilize the host's hemoproteins. Once internalized, heme is cleaved by both oxidative and nonoxidative mechanisms to release iron. Heme, itself a lipophilic and toxic molecule, presents a significant challenge for transport into the cell. As such, pathogenic bacteria have evolved sophisticated cell surface signaling and transport systems to obtain heme from the host. In this review, we summarize the structure and function of the heme-sensing and transport systems of pathogenic bacteria and the potential of these systems as antimicrobial targets.
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Affiliation(s)
- Weiliang Huang
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201;
| | - Angela Wilks
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201;
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13
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Rapid Heme Transfer Reactions between NEAr Transporter Domains of Staphylococcus aureus: A Theoretical Study Using QM/MM and MD Simulations. PLoS One 2015; 10:e0145125. [PMID: 26658942 PMCID: PMC4684392 DOI: 10.1371/journal.pone.0145125] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2015] [Accepted: 11/29/2015] [Indexed: 11/19/2022] Open
Abstract
In vertebrates, most iron is present as heme or is chelated by proteins. Thus, Gram-positive pathogens such as Staphylococcus aureus have evolved an iron-regulated surface determinant (Isd) system that transports heme across thick cell walls into the cytoplasm. Recent studies have demonstrated that heme is rapidly transferred between the NEAr Transporter (NEAT) domains of the Isd system, despite its high affinity toward each domain, suggesting the presence of an intermediate NEAT•heme•NEAT complex. In the present study, we performed short restrained molecular dynamics (MD) simulations to dock the acceptor NEAT domain to the donor NEAT•heme complex and obtained models where the two NEAT domains were arranged with two-fold pseudo symmetry around the heme molecule. After turning off the restraints, complex structures were stably maintained during subsequent unrestrained MD simulations, except for the hydrogen bond between the propionate group of the heme molecule and the donor NEAT domain, potentially facilitating the transition of heme from the donor to the acceptor. Subsequent structural optimization using the quantum mechanics/molecular mechanics (QM/MM) method showed that two tyrosine residues, one from each NEAT domain, were simultaneously coordinated to the ferric heme iron in the intermediate complex only if they were deprotonated. Based on these results, we propose a reaction scheme for heme transfer between NEAT domains.
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14
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Bennett EH, Akbas N, Adrian SA, Lukat-Rodgers GS, Collins DP, Dawson JH, Allen CE, Schmitt MP, Rodgers KR, Dixon DW. Heme Binding by Corynebacterium diphtheriae HmuT: Function and Heme Environment. Biochemistry 2015; 54:6598-609. [PMID: 26478504 PMCID: PMC4943319 DOI: 10.1021/acs.biochem.5b00666] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The heme uptake pathway (hmu) of Corynebacterium diphtheriae utilizes multiple proteins to bind and transport heme into the cell. One of these proteins, HmuT, delivers heme to the ABC transporter HmuUV. In this study, the axial ligation of the heme in ferric HmuT is probed by examination of wild-type (WT) HmuT and a series of conserved heme pocket residue mutants, H136A, Y235A, and M292A. Characterization by UV-visible, resonance Raman, and magnetic circular dichroism spectroscopies indicates that H136 and Y235 are the axial ligands in ferric HmuT. Consistent with this assignment of axial ligands, ferric WT and H136A HmuT are difficult to reduce while Y235A is reduced readily in the presence of dithionite. The FeCO Raman shifts in WT, H136A, and Y235A HmuT-CO complexes provide further evidence of the axial ligand assignments. Additionally, these frequencies provide insight into the nonbonding environment of the heme pocket. Ferrous Y235A and the Y235A-CO complex reveal that the imidazole of H136 exists in two forms, one neutral and one with imidazolate character, consistent with a hydrogen bond acceptor on the H136 side of the heme. The ferric fluoride complex of Y235A reveals the presence of at least one hydrogen bond donor on the Y235 side of the heme. Hemoglobin utilization assays showed that the axial Y235 ligand is required for heme uptake in HmuT.
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Affiliation(s)
| | - Neval Akbas
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302-3965
| | - Seth A. Adrian
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050
| | - Gudrun S. Lukat-Rodgers
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050
| | - Daniel P. Collins
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208
| | - John H. Dawson
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208
| | - Courtni E. Allen
- Laboratory of Respiratory and Special Pathogens, Division of Bacterial, Parasitic, and Allergenic Products, Center for Biologics Evaluation, and Research, Food and Drug Administration, Silver Spring, Maryland 20993
| | - Michael P. Schmitt
- Laboratory of Respiratory and Special Pathogens, Division of Bacterial, Parasitic, and Allergenic Products, Center for Biologics Evaluation, and Research, Food and Drug Administration, Silver Spring, Maryland 20993
| | - Kenton R. Rodgers
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108-6050
| | - Dabney W. Dixon
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302-3965
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15
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Abi-Khalil E, Segond D, Terpstra T, André-Leroux G, Kallassy M, Lereclus D, Bou-Abdallah F, Nielsen-Leroux C. Heme interplay between IlsA and IsdC: Two structurally different surface proteins from Bacillus cereus. Biochim Biophys Acta Gen Subj 2015; 1850:1930-41. [PMID: 26093289 DOI: 10.1016/j.bbagen.2015.06.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Revised: 06/04/2015] [Accepted: 06/16/2015] [Indexed: 12/16/2022]
Abstract
BACKGROUND Iron is an essential element for bacterial growth and virulence. Because of its limited bioavailability in the host, bacteria have adapted several strategies to acquire iron during infection. In the human opportunistic bacteria Bacillus cereus, a surface protein IlsA is shown to be involved in iron acquisition from both ferritin and hemoproteins. IlsA has a modular structure consisting of a NEAT (Near Iron transporter) domain at the N-terminus, several LRR (Leucine Rich Repeat) motifs and a SLH (Surface Layer Homology) domain likely involved in anchoring the protein to the cell surface. METHODS Isothermal titration calorimetry, UV-Vis spectrophotometry, affinity chromatography and rapid kinetics stopped-flow measurements were employed to probe the binding and transfer of hemin between two different B. cereus surface proteins (IlsA and IsdC). RESULTS IlsA binds hemin via the NEAT domain and is able to extract heme from hemoglobin whereas the LRR domain alone is not involved in these processes. A rapid hemin transfer from hemin-containing IlsA (holo-IlsA) to hemin-free IsdC (apo-IsdC) is demonstrated. CONCLUSIONS For the first time, it is shown that two different B. cereus surface proteins (IlsA and IsdC) can interact and transfer heme suggesting their involvement in B. cereus heme acquisition. GENERAL SIGNIFICANCE An important role for the complete Isd system in heme-associated bacterial growth is demonstrated and new insights into the interplay between an Isd NEAT surface protein and an IlsA-NEAT-LRR protein, both of which appear to be involved in heme-iron acquisition in B. cereus are revealed.
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Affiliation(s)
- Elise Abi-Khalil
- INRA, UMR 1319 Micalis-AgroParisTech, AgroParisTech UMR Micalis, F-78352 Jouy en Josas, France; Laboratory of Biotechnology, Saint-Joseph University, Beyrouth, Lebanon; Department of Chemistry, State University of New York at Potsdam, Potsdam, NY 13676, USA
| | - Diego Segond
- INRA, UMR 1319 Micalis-AgroParisTech, AgroParisTech UMR Micalis, F-78352 Jouy en Josas, France
| | - Tyson Terpstra
- Department of Chemistry, State University of New York at Potsdam, Potsdam, NY 13676, USA
| | | | - Mireille Kallassy
- Laboratory of Biotechnology, Saint-Joseph University, Beyrouth, Lebanon
| | - Didier Lereclus
- INRA, UMR 1319 Micalis-AgroParisTech, AgroParisTech UMR Micalis, F-78352 Jouy en Josas, France
| | - Fadi Bou-Abdallah
- Department of Chemistry, State University of New York at Potsdam, Potsdam, NY 13676, USA
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16
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Dickson CF, Jacques DA, Clubb RT, Guss JM, Gell DA. The structure of haemoglobin bound to the haemoglobin receptor IsdH from Staphylococcus aureus shows disruption of the native α-globin haem pocket. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2015; 71:1295-306. [PMID: 26057669 PMCID: PMC8518021 DOI: 10.1107/s1399004715005817] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Accepted: 03/23/2015] [Indexed: 12/13/2022]
Abstract
Staphylococcus aureus is a common and serious cause of infection in humans. The bacterium expresses a cell-surface receptor that binds to, and strips haem from, human haemoglobin (Hb). The binding interface has previously been identified; however, the structural changes that promote haem release from haemoglobin were unknown. Here, the structure of the receptor-Hb complex is reported at 2.6 Å resolution, which reveals a conformational change in the α-globin F helix that disrupts the haem-pocket structure and alters the Hb quaternary interactions. These features suggest potential mechanisms by which the S. aureus Hb receptor induces haem release from Hb.
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17
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Renberg RL, Yuan X, Samuel TK, Miguel DC, Hamza I, Andrews NW, Flannery AR. The Heme Transport Capacity of LHR1 Determines the Extent of Virulence in Leishmania amazonensis. PLoS Negl Trop Dis 2015; 9:e0003804. [PMID: 26001191 PMCID: PMC4441390 DOI: 10.1371/journal.pntd.0003804] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 05/01/2015] [Indexed: 12/14/2022] Open
Abstract
Leishmania spp. are trypanosomatid parasites that replicate intracellularly in macrophages, causing serious human morbidity and mortality throughout the world. Trypanosomatid protozoa cannot synthesize heme, so must acquire this essential cofactor from their environment. Earlier studies identified LHR1 as a Leishmania amazonensis transmembrane protein that mediates heme uptake. Null mutants of LHR1 are not viable and single knockout strains have reduced virulence, but very little is known about the properties of LHR1 directly associated with heme transport. Here, we use functional assays in Saccharomyces cerevisiae to show that specific tyrosine residues within the first three predicted transmembrane domains of LHR1 are required for efficient heme uptake. These tyrosines are unique to LHR1, consistent with the low similarity between LHR1 and its corresponding homologs in C. elegans and human. Substitution of these tyrosines in LHR1 resulted in varying degrees of heme transport inhibition, phenotypes that closely mirrored the impaired ability of L. amazonensis to replicate as intracellular amastigotes in macrophages and generate cutaneous lesions in mice. Taken together, our results imply that the mechanism for heme transport by LHR1 is distinctive and may have adapted to secure heme, a limiting cofactor, inside the host. Since LHR1 is significantly divergent from the human heme transporter HRG1, our findings lay the groundwork for selective targeting of LHR1 by small molecule antagonists. Leishmania are protozoan parasites that infect humans and replicate intracellularly in macrophages, cells normally engaged in protecting the host from pathogens. These parasites have several strategies to survive inside the hostile environment of the host macrophage, and one of these strategies involves heme acquisition. Heme is an iron-containing molecule that is essential for many cellular functions. Unlike mammalian cells, Leishmania parasites cannot synthesize heme, so must acquire it from the host cell. In earlier work we found that the parasites express a surface protein, LHR1, which transports heme into the parasites. In this study we identified specific amino acids in LHR1 that are required for heme transport. When expressed in yeast cells, LHR1 carrying these mutations had defects in heme transport that were equivalent to the inhibition in virulence observed when these proteins were expressed in Leishmania and tested in macrophage and mouse infection assays. These critical amino acids do not exist in the human heme transporter, indicating that LHR1 is a promising target for the development of specific drugs for the treatment of leishmaniasis and possibly other serious parasitic diseases, such as Chagas’ disease and sleeping sickness.
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Affiliation(s)
- Rebecca L. Renberg
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, United States of America
| | - Xiaojing Yuan
- Department of Animal and Avian Sciences, University of Maryland, College Park, Maryland, United States of America
| | - Tamika K. Samuel
- Department of Animal and Avian Sciences, University of Maryland, College Park, Maryland, United States of America
| | - Danilo C. Miguel
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, United States of America
| | - Iqbal Hamza
- Department of Animal and Avian Sciences, University of Maryland, College Park, Maryland, United States of America
| | - Norma W. Andrews
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, United States of America
- * E-mail: ,
| | - Andrew R. Flannery
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, United States of America
- PathSensors, Inc., Baltimore, Maryland, United States of America
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18
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Smith AD, Modi AR, Sun S, Dawson JH, Wilks A. Spectroscopic Determination of Distinct Heme Ligands in Outer-Membrane Receptors PhuR and HasR of Pseudomonas aeruginosa. Biochemistry 2015; 54:2601-12. [PMID: 25849630 DOI: 10.1021/acs.biochem.5b00017] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Pseudomonas aeruginosa PAO1 encodes two outer membrane receptors, PhuR (Pseudomonas heme uptake) and HasR (heme assimilation system). The HasR receptor acquires heme through interaction with a secreted hemophore, HasAp. The non-hemophore-dependent PhuR is encoded along with proteins required for heme translocation into the cytoplasm. Herein, we report the isolation and characterization of the HasR and PhuR receptors. Absorption and MCD spectroscopy confirmed that, similar to other Gram-negative OM receptors, HasR coordinates heme through the conserved N-terminal plug His-221 and His-624 of the surface-exposed FRAP-loop. In contrast, PhuR showed distinct absorption and MCD spectra consistent with coordination through a Tyr residue. Sequence alignment of PhuR with all known Gram-negative OM heme receptors revealed a lack of a conserved His within the FRAP loop but two Tyr residues at positions 519 and 529. Site-directed mutagenesis and spectroscopic characterization confirmed Tyr-519 and the N-terminal plug His-124 provide the heme ligands in PhuR. We propose that PhuR and HasR represent nonredundant heme receptors capable of sensing and accessing heme across a wide range of physiological conditions on colonization and infection of the host.
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Affiliation(s)
- Aaron D Smith
- †Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201, United States
| | - Anuja R Modi
- ‡Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Shengfang Sun
- ‡Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - John H Dawson
- ‡Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Angela Wilks
- †Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201, United States
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19
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Sheldon JR, Heinrichs DE. Recent developments in understanding the iron acquisition strategies of gram positive pathogens. FEMS Microbiol Rev 2015; 39:592-630. [DOI: 10.1093/femsre/fuv009] [Citation(s) in RCA: 166] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/04/2015] [Indexed: 12/26/2022] Open
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20
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Smith AD, Wilks A. Differential contributions of the outer membrane receptors PhuR and HasR to heme acquisition in Pseudomonas aeruginosa. J Biol Chem 2015; 290:7756-66. [PMID: 25616666 DOI: 10.1074/jbc.m114.633495] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Pseudomonas aeruginosa PAO1 encodes two outer membrane receptors, PhuR (Pseudomonas heme uptake) and HasR (heme assimilation system). The HasR and PhuR receptors have distinct heme coordinating ligands and substrate specificities. HasR is encoded in an operon with a secreted hemophore, HasAp. In contrast the non-hemophore-dependent PhuR is encoded within an operon along with proteins required for heme translocation into the cytoplasm. Herein we report on the contributions of the HasR and PhuR receptors to heme uptake and utilization. Employing bacterial genetics and isotopic [(13)C]heme labeling studies we have shown both PhuR and HasR are required for optimal heme utilization. However, the unique His-Tyr-ligated PhuR plays a major role in the acquisition of heme. In contrast the HasR receptor plays a primary role in the sensing of extracellular heme and a supplementary role in heme uptake. We propose PhuR and HasR represent non-redundant heme receptors, capable of accessing heme across a wide range of physiological conditions on colonization of the host.
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Affiliation(s)
- Aaron D Smith
- From the Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201
| | - Angela Wilks
- From the Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201
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21
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Ascenzi P, di Masi A, Leboffe L, Frangipani E, Nardini M, Verde C, Visca P. Structural Biology of Bacterial Haemophores. Adv Microb Physiol 2015; 67:127-76. [PMID: 26616517 DOI: 10.1016/bs.ampbs.2015.09.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Iron plays a key role in a wide range of metabolic and signalling functions representing an essential nutrient for almost all forms of life. However, the ferric form is hardly soluble, whereas the ferrous form is highly toxic. Thus, in biological fluids, most of the iron is sequestered in iron- or haem-binding proteins and the level of free iron is low, making haem and iron acquisition a challenge for pathogenic bacteria during infections. Although toxic to the host, free haem is a major and readily available source of iron for several pathogenic microorganisms. Both Gram-positive and Gram-negative bacteria have developed several strategies to acquire free haem-Fe and protein-bound haem-Fe. Haemophores are a class of secreted and cell surface-exposed proteins promoting free-haem uptake, haem extraction from host haem proteins, and haem presentation to specific outer-membrane receptors that internalize the metal-porphyrins. Here, structural biology of bacterial haemophores is reviewed focusing on haem acquisition, haem internalization, and haem-degrading systems.
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Affiliation(s)
- Paolo Ascenzi
- Laboratorio Interdipartimentale di Microscopia Elettronica, Università Roma Tre, Roma, Italy; Istituto di Bioscienze e BioRisorse, Consiglio Nazionale delle Ricerche, Napoli, Italy.
| | | | - Loris Leboffe
- Dipartimento di Scienze, Università Roma Tre, Roma, Italy
| | | | - Marco Nardini
- Dipartimento di Bioscienze, Università di Milano, Milano, Italy
| | - Cinzia Verde
- Istituto di Bioscienze e BioRisorse, Consiglio Nazionale delle Ricerche, Napoli, Italy; Dipartimento di Scienze, Università Roma Tre, Roma, Italy
| | - Paolo Visca
- Dipartimento di Scienze, Università Roma Tre, Roma, Italy
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22
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Malmirchegini GR, Sjodt M, Shnitkind S, Sawaya MR, Rosinski J, Newton SM, Klebba PE, Clubb RT. Novel mechanism of hemin capture by Hbp2, the hemoglobin-binding hemophore from Listeria monocytogenes. J Biol Chem 2014; 289:34886-99. [PMID: 25315777 DOI: 10.1074/jbc.m114.583013] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Iron is an essential nutrient that is required for the growth of the bacterial pathogen Listeria monocytogenes. In cell cultures, this microbe secretes hemin/hemoglobin-binding protein 2 (Hbp2; Lmo2185) protein, which has been proposed to function as a hemophore that scavenges heme from the environment. Based on its primary sequence, Hbp2 contains three NEAr transporter (NEAT) domains of unknown function. Here we show that each of these domains mediates high affinity binding to ferric heme (hemin) and that its N- and C-terminal domains interact with hemoglobin (Hb). The results of hemin transfer experiments are consistent with Hbp2 functioning as an Hb-binding hemophore that delivers hemin to other Hbp2 proteins that are attached to the cell wall. Surprisingly, our work reveals that the central NEAT domain in Hbp2 binds hemin even though its primary sequence lacks a highly conserved YXXXY motif that is used by all other previously characterized NEAT domains to coordinate iron in the hemin molecule. To elucidate the mechanism of hemin binding by Hbp2, we determined crystal structures of its central NEAT domain (Hbp2(N2); residues 183-303) in its free and hemin-bound states. The structures reveal an unprecedented mechanism of hemin binding in which Hbp2(N2) undergoes a major conformational rearrangement that facilitates metal coordination by a non-canonical tyrosine residue. These studies highlight previously unrecognized plasticity in the hemin binding mechanism of NEAT domains and provide insight into how L. monocytogenes captures heme iron.
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Affiliation(s)
- G Reza Malmirchegini
- From the Department of Chemistry and Biochemistry and the UCLA-Department of Energy Institute for Genomics and Proteomics, UCLA, Los Angeles, California 90095 and
| | - Megan Sjodt
- From the Department of Chemistry and Biochemistry and the UCLA-Department of Energy Institute for Genomics and Proteomics, UCLA, Los Angeles, California 90095 and
| | - Sergey Shnitkind
- From the Department of Chemistry and Biochemistry and the UCLA-Department of Energy Institute for Genomics and Proteomics, UCLA, Los Angeles, California 90095 and
| | - Michael R Sawaya
- From the Department of Chemistry and Biochemistry and the UCLA-Department of Energy Institute for Genomics and Proteomics, UCLA, Los Angeles, California 90095 and Howard Hughes Medical Institute and
| | - Justin Rosinski
- From the Department of Chemistry and Biochemistry and the UCLA-Department of Energy Institute for Genomics and Proteomics, UCLA, Los Angeles, California 90095 and
| | - Salete M Newton
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66502
| | - Phillip E Klebba
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66502
| | - Robert T Clubb
- From the Department of Chemistry and Biochemistry and the UCLA-Department of Energy Institute for Genomics and Proteomics, UCLA, Los Angeles, California 90095 and
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23
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Molecular and evolutionary analysis of NEAr-iron Transporter (NEAT) domains. PLoS One 2014; 9:e104794. [PMID: 25153520 PMCID: PMC4143258 DOI: 10.1371/journal.pone.0104794] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 07/18/2014] [Indexed: 12/25/2022] Open
Abstract
Iron is essential for bacterial survival, being required for numerous biological processes. NEAr-iron Transporter (NEAT) domains have been studied in pathogenic Gram-positive bacteria to understand how their proteins obtain heme as an iron source during infection. While a 2002 study initially discovered and annotated the NEAT domain encoded by the genomes of several Gram-positive bacteria, there remains a scarcity of information regarding the conservation and distribution of NEAT domains throughout the bacterial kingdom, and whether these domains are restricted to pathogenic bacteria. This study aims to expand upon initial bioinformatics analysis of predicted NEAT domains, by exploring their evolution and conserved function. This information was used to identify new candidate domains in both pathogenic and nonpathogenic organisms. We also searched metagenomic datasets, specifically sequence from the Human Microbiome Project. Here, we report a comprehensive phylogenetic analysis of 343 NEAT domains, encoded by Gram-positive bacteria, mostly within the phylum Firmicutes, with the exception of Eggerthella sp. (Actinobacteria) and an unclassified Mollicutes bacterium (Tenericutes). No new NEAT sequences were identified in the HMP dataset. We detected specific groups of NEAT domains based on phylogeny of protein sequences, including a cluster of novel clostridial NEAT domains. We also identified environmental and soil organisms that encode putative NEAT proteins. Biochemical analysis of heme binding by a NEAT domain from a protein encoded by the soil-dwelling organism Paenibacillus polymyxa demonstrated that the domain is homologous in function to NEAT domains encoded by pathogenic bacteria. Together, this study provides the first global bioinformatics analysis and phylogenetic evidence that NEAT domains have a strong conservation of function, despite group-specific differences at the amino acid level. These findings will provide information useful for future projects concerning the structure and function of NEAT domains, particularly in pathogens where they have yet to be studied.
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24
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Fonner BA, Tripet BP, Eilers BJ, Stanisich J, Sullivan-Springhetti RK, Moore R, Liu M, Lei B, Copié V. Solution structure and molecular determinants of hemoglobin binding of the first NEAT domain of IsdB in Staphylococcus aureus. Biochemistry 2014; 53:3922-33. [PMID: 24871270 PMCID: PMC4072347 DOI: 10.1021/bi5005188] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
![]()
The
human pathogen Staphylococcus aureus acquires heme iron from hemoglobin (Hb) via the action of a series
of iron-regulated surface determinant (Isd) proteins. The cell wall
anchored IsdB protein is recognized as the predominant Hb receptor,
and is comprised of two NEAr transporter (NEAT) domains that act in
concert to bind, extract, and transfer heme from Hb to downstream
Isd proteins. Structural details of the NEAT 2 domain of IsdB have
been investigated, but the molecular coordination between NEAT 2 and
NEAT 1 to extract heme from hemoglobin has yet to be characterized.
To obtain a more complete understanding of IsdB structure and function,
we have solved the 3D solution structure of the NEAT 1 domain of IsdB
(IsdBN1) spanning residues 125–272 of the full-length
protein by NMR. The structure reveals a canonical NEAT domain fold
and has particular structural similarity to the NEAT 1 and NEAT 2
domains of IsdH, which also interact with Hb. IsdBN1 is
also comprised of a short N-terminal helix, which has not been previously
observed in other NEAT domain structures. Interestingly, the Hb binding
region (loop 2 of IsdBN1) is disordered in solution. Analysis
of Hb binding demonstrates that IsdBN1 can bind metHb weakly
and the affinity of this interaction is further increased by the presence
of IsdB linker domain. IsdBN1 loop 2 variants reveal that
phenylalanine 164 (F164) of IsdB is necessary for Hb binding and rapid
heme transfer from metHb to IsdB. Together, these findings provide
a structural role for IsdBN1 in enhancing the rate of extraction
of metHb heme by the IsdB NEAT 2 domain.
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Affiliation(s)
- Brittany A Fonner
- Department of Chemistry and Biochemistry, Montana State University , 103 Chemistry and Biochemistry Building, PO Box 173400, Bozeman, Montana 59717-3400, United States
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25
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Bowden CFM, Verstraete MM, Eltis LD, Murphy MEP. Hemoglobin binding and catalytic heme extraction by IsdB near iron transporter domains. Biochemistry 2014; 53:2286-94. [PMID: 24645787 DOI: 10.1021/bi500230f] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Isd (iron-regulated surface determinant) system is a multiprotein transporter that allows bacterium Staphylococcus aureus to take up iron from hemoglobin (Hb) during human infection. In this system, IsdB is a cell wall-anchored surface protein that contains two near iron transporter (NEAT) domains, one of which binds heme. IsdB rapidly extracts heme from Hb and transfers it to IsdA for relay into the bacterial cell. Using a series of recombinant IsdB constructs that included at least one NEAT domain, we demonstrated that both domains are required to bind Hb with high affinity (KD = 0.42 ± 0.05 μM) and to extract heme from Hb. Moreover, IsdB extracted heme only from oxidized metHb, although it also bound oxyHb and the Hb-CO complex. In a reconstituted model of the biological heme relay pathway, IsdB catalyzed the transfer of heme from metHb to IsdA with a Km for metHb of 0.75 ± 0.07 μN and a kcat of 0.22 ± 0.01 s(-1). The latter is consistent with the transfer of heme from metHb to IsdB being the rate-limiting step. With both NEAT domains and the linker region present in a single contiguous polypeptide, high-affinity Hb binding was achieved, rapid heme uptake was observed, and multiple turnovers of heme extraction from metHb and transfer to IsdA were conducted, representing all known Hb-heme uptake functions of the full-length IsdB protein.
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Affiliation(s)
- Catherine F M Bowden
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia , Vancouver, BC, Canada V6T 1Z3
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26
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Dickson CF, Kumar KK, Jacques DA, Malmirchegini GR, Spirig T, Mackay JP, Clubb RT, Guss JM, Gell DA. Structure of the hemoglobin-IsdH complex reveals the molecular basis of iron capture by Staphylococcus aureus. J Biol Chem 2014; 289:6728-6738. [PMID: 24425866 DOI: 10.1074/jbc.m113.545566] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Staphylococcus aureus causes life-threatening disease in humans. The S. aureus surface protein iron-regulated surface determinant H (IsdH) binds to mammalian hemoglobin (Hb) and extracts heme as a source of iron, which is an essential nutrient for the bacteria. However, the process of heme transfer from Hb is poorly understood. We have determined the structure of IsdH bound to human Hb by x-ray crystallography at 4.2 Å resolution, revealing the structural basis for heme transfer. One IsdH molecule is bound to each α and β Hb subunit, suggesting that the receptor acquires iron from both chains by a similar mechanism. Remarkably, two near iron transporter (NEAT) domains in IsdH perform very different functions. An N-terminal NEAT domain binds α/β globin through a site distant from the globin heme pocket and, via an intervening structural domain, positions the C-terminal heme-binding NEAT domain perfectly for heme transfer. These data, together with a 2.3 Å resolution crystal structure of the isolated N-terminal domain bound to Hb and small-angle x-ray scattering of free IsdH, reveal how multiple domains of IsdH cooperate to strip heme from Hb. Many bacterial pathogens obtain iron from human hemoglobin using proteins that contain multiple NEAT domains and other domains whose functions are poorly understood. Our results suggest that, rather than acting as isolated units, NEAT domains may be integrated into higher order architectures that employ multiple interaction interfaces to efficiently extract heme from host proteins.
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Affiliation(s)
- Claire F Dickson
- Menzies Research Institute Tasmania, University of Tasmania, Hobart, Tasmania 7000, Australia
| | - Kaavya Krishna Kumar
- School of Molecular Bioscience, University of Sydney, Sydney, New South Wales 2006, Australia
| | - David A Jacques
- School of Molecular Bioscience, University of Sydney, Sydney, New South Wales 2006, Australia
| | | | - Thomas Spirig
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095
| | - Joel P Mackay
- School of Molecular Bioscience, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Robert T Clubb
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095
| | - J Mitchell Guss
- School of Molecular Bioscience, University of Sydney, Sydney, New South Wales 2006, Australia
| | - David A Gell
- Menzies Research Institute Tasmania, University of Tasmania, Hobart, Tasmania 7000, Australia.
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Pishchany G, Sheldon JR, Dickson CF, Alam MT, Read TD, Gell DA, Heinrichs DE, Skaar EP. IsdB-dependent hemoglobin binding is required for acquisition of heme by Staphylococcus aureus. J Infect Dis 2013; 209:1764-72. [PMID: 24338348 DOI: 10.1093/infdis/jit817] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Staphylococcus aureus is a Gram-positive pathogen responsible for tremendous morbidity and mortality. As with most bacteria, S. aureus requires iron to cause disease, and it can acquire iron from host hemoglobin. The current model for staphylococcal hemoglobin-iron acquisition proposes that S. aureus binds hemoglobin through the surface-exposed hemoglobin receptor IsdB. IsdB removes heme from bound hemoglobin and transfers this cofactor to other proteins of the Isd system, which import and degrade heme to release iron in the cytoplasm. Here we demonstrate that the individual components of the Isd system are required for growth on low nanomolar concentrations of hemoglobin as a sole source of iron. An in-depth study of hemoglobin binding by IsdB revealed key residues that are required for hemoglobin binding. Further, we show that these residues are necessary for heme extraction from hemoglobin and growth on hemoglobin as a sole iron source. These processes are found to contribute to the pathogenicity of S. aureus in a murine model of infection. Together these results build on the model for Isd-mediated hemoglobin binding and heme-iron acquisition during the pathogenesis of S. aureus infection.
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Affiliation(s)
- Gleb Pishchany
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee
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28
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Ouattara M, Pennati A, Devlin DJ, Huang YS, Gadda G, Eichenbaum Z. Kinetics of heme transfer by the Shr NEAT domains of Group A Streptococcus. Arch Biochem Biophys 2013; 538:71-9. [PMID: 23993953 DOI: 10.1016/j.abb.2013.08.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Revised: 08/06/2013] [Accepted: 08/14/2013] [Indexed: 01/07/2023]
Abstract
The hemolytic Group A Streptococcus (GAS) is a notorious human pathogen. Shr protein of GAS participates in iron acquisition by obtaining heme from host hemoglobin and delivering it to the adjacent receptor on the surface, Shp. Heme is then conveyed to the SiaABC proteins for transport across the membrane. Using rapid kinetic studies, we investigated the role of the two heme binding NEAT modules of Shr. Stopped-flow analysis showed that holoNEAT1 quickly delivered heme to apoShp. HoloNEAT2 did not exhibit such activity; only little and slow transfer of heme from NEAT2 to apoShp was seen, suggesting that Shr NEAT domains have distinctive roles in heme transport. HoloNEAT1 also provided heme to apoNEAT2, by a fast and reversible process. To the best of our knowledge this is the first transfer observed between isolated NEAT domains of the same receptor. Sequence alignment revealed that Shr NEAT domains belong to two families of NEAT domains that are conserved in Shr orthologs from several species. Based on the heme transfer kinetics, we propose that Shr proteins modulate heme uptake according to heme availability by a mechanism where NEAT1 facilitates fast heme delivery to Shp, whereas NEAT2 serves as a temporary storage for heme on the bacterial surface.
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Affiliation(s)
- Mahamoudou Ouattara
- Department of Biology, College of Arts and Sciences, Georgia State University, Atlanta, GA 30303, USA
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29
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Vu NT, Moriwaki Y, Caaveiro JMM, Terada T, Tsutsumi H, Hamachi I, Shimizu K, Tsumoto K. Selective binding of antimicrobial porphyrins to the heme-receptor IsdH-NEAT3 of Staphylococcus aureus. Protein Sci 2013; 22:942-53. [PMID: 23649633 DOI: 10.1002/pro.2276] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 04/24/2013] [Accepted: 04/25/2013] [Indexed: 12/20/2022]
Abstract
The Isd (iron-regulated surface determinant) system of the human pathogen Staphylococcus aureus is responsible for the acquisition of heme from the host organism. We recently reported that the extracellular heme receptor IsdH-NEAT3 captures and transfers noniron antimicrobial porphyrins containing metals in oxidation state (III). However, it is unclear if geometric factors such as the size of the metal (ionic radius) affect binding and transfer of metalloporphyrins. We carried out an ample structural, functional, and thermodynamic analysis of the binding properties of antimicrobial indium(III)-porphyrin, which bears a much larger metal ion than the iron(III) of the natural ligand heme. The results demonstrate that the NEAT3 receptor recognizes the In(III)-containing PPIX in a manner very similar to that of heme. Site-directed mutagenesis identifies Tyr642 as the central element in the recognition mechanism as suggested from the crystal structures. Importantly, the NEAT3 receptor possesses the remarkable ability to capture dimers of metalloporphyrin. Molecular dynamics simulations reveal that IsdH-NEAT3 does not require conformational changes, or large rearrangements of the residues within its binding site, to accommodate the much larger (heme)2 ligand. We discuss the implications of these findings for the design of potent inhibitors against this family of key receptors of S. aureus.
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Affiliation(s)
- Nhuan T Vu
- Medical Proteomics Laboratory, Institute of Medical Science, The University of Tokyo, Tokyo, 108-8639, Japan
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30
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Pishchany G, Haley KP, Skaar EP. Staphylococcus aureus growth using human hemoglobin as an iron source. J Vis Exp 2013:50072. [PMID: 23426144 DOI: 10.3791/50072] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
S. aureus is a pathogenic bacterium that requires iron to carry out vital metabolic functions and cause disease. The most abundant reservoir of iron inside the human host is heme, which is the cofactor of hemoglobin. To acquire iron from hemoglobin, S. aureus utilizes an elaborate system known as the iron-regulated surface determinant (Isd) system. Components of the Isd system first bind host hemoglobin, then extract and import heme, and finally liberate iron from heme in the bacterial cytoplasm. This pathway has been dissected through numerous in vitro studies. Further, the contribution of the Isd system to infection has been repeatedly demonstrated in mouse models. Establishing the contribution of the Isd system to hemoglobin-derived iron acquisition and growth has proven to be more challenging. Growth assays using hemoglobin as a sole iron source are complicated by the instability of commercially available hemoglobin, contaminating free iron in the growth medium, and toxicity associated with iron chelators. Here we present a method that overcomes these limitations. High quality hemoglobin is prepared from fresh blood and is stored in liquid nitrogen. Purified hemoglobin is supplemented into iron-deplete medium mimicking the iron-poor environment encountered by pathogens inside the vertebrate host. By starving S. aureus of free iron and supplementing with a minimally manipulated form of hemoglobin we induce growth in a manner that is entirely dependent on the ability to bind hemoglobin, extract heme, pass heme through the bacterial cell envelope and degrade heme in the cytoplasm. This assay will be useful for researchers seeking to elucidate the mechanisms of hemoglobin-/heme-derived iron acquisition in S. aureus and possibly other bacterial pathogens.
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Affiliation(s)
- Gleb Pishchany
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical School, Nashville, TN, USA
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31
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Honsa ES, Owens CP, Goulding CW, Maresso AW. The near-iron transporter (NEAT) domains of the anthrax hemophore IsdX2 require a critical glutamine to extract heme from methemoglobin. J Biol Chem 2013; 288:8479-8490. [PMID: 23364793 DOI: 10.1074/jbc.m112.430009] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Several gram-positive pathogenic bacteria employ near-iron transporter (NEAT) domains to acquire heme from hemoglobin during infection. However, the structural requirements and mechanism of action for NEAT-mediated heme extraction remains unknown. Bacillus anthracis exhibits a rapid growth rate during systemic infection, suggesting that the bacterium expresses efficient iron acquisition systems. To understand how B. anthracis acquires iron from heme sources, which account for 80% of mammalian iron stores, we investigated the properties of the five-NEAT domain hemophore IsdX2. Using a combination of bioinformatics and site-directed mutagenesis, we determined that the heme extraction properties of IsdX2 are dependent on an amino acid with an amide side chain within the 310-helix of the NEAT domain. Additionally, we used a spectroscopic analysis to show that IsdX2 NEAT domains only scavenge heme from methemoglobin (metHb) and that autoxidation of oxyhemoglobin to metHb must occur prior to extraction. We also report the crystal structures of NEAT5 wild type and a Q29T mutant and present surface plasmon resonance data that indicate that the loss of this amide side chain reduces the affinity of the NEAT domain for metHb. We propose a model whereby the amide side chain is first required to drive an interaction with metHb that destabilizes heme, which is subsequently extracted and coordinated in the aliphatic heme-binding environment of the NEAT domain. Because an amino acid with an amide side chain in this position is observed in NEAT domains of several genera of gram-positive pathogenic bacteria, these results suggest that specific targeting of this or nearby residues may be an entry point for inhibitor development aimed at blocking bacterial iron acquisition during infection.
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Affiliation(s)
- Erin S Honsa
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas 77030
| | - Cedric P Owens
- Departments of Molecular Biology and Biochemistry, University of California, Irvine, California 92617
| | - Celia W Goulding
- Departments of Molecular Biology and Biochemistry, University of California, Irvine, California 92617
| | - Anthony W Maresso
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas 77030.
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32
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Zapotoczna M, Jevnikar Z, Miajlovic H, Kos J, Foster TJ. Iron-regulated surface determinant B (IsdB) promotes Staphylococcus aureus adherence to and internalization by non-phagocytic human cells. Cell Microbiol 2013; 15:1026-41. [PMID: 23279065 DOI: 10.1111/cmi.12097] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 11/28/2012] [Accepted: 12/13/2012] [Indexed: 01/22/2023]
Abstract
Staphylococcus aureus is a human pathogen that causes invasive and recurring infections. The ability to internalize into and persist within host cells is thought to contribute to infection. Here we report a novel role for the well-characterized iron-regulated surface determinant B (IsdB) protein which we have shown can promote adhesion of 293T, HeLa cells and platelets to immobilized bacteria independently of its ability to bind haemoglobin. IsdB bound to the active form of the platelet integrin αIIb β3 , both on platelets and when the integrin was expressed ectopically in CHO cells. IsdB also promoted bacterial invasion into human cells. This was clearly demonstrated with bacteria lacking fibronectin-binding proteins (FnBPs), which are known to promote invasion in the presence of fibronectin. However, IsdB also contributed significantly to invasion by cells expressing FnBPs in the presence of serum. Thus IsdB appears to be able to interact with the broader family of integrins that bind ligands with the RGD motif and to act as a back up mechanism to promote interactions with mammalian cells.
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Affiliation(s)
- Marta Zapotoczna
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College Dublin, Dublin 2, Ireland
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33
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Tiedemann MT, Heinrichs DE, Stillman MJ. Multiprotein Heme Shuttle Pathway in Staphylococcus aureus: Iron-Regulated Surface Determinant Cog-Wheel Kinetics. J Am Chem Soc 2012; 134:16578-85. [DOI: 10.1021/ja305115y] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Michael T. Tiedemann
- Department of Chemistry, The University of Western Ontario, London, Ontario,
Canada, N6A 5B7
| | - David E. Heinrichs
- Department
of Microbiology and
Immunology, The University of Western Ontario, London, Ontario, Canada, N6A 5C1
| | - Martin J. Stillman
- Department of Chemistry, The University of Western Ontario, London, Ontario,
Canada, N6A 5B7
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34
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Iron-regulated surface determinant (Isd) proteins of Staphylococcus lugdunensis. J Bacteriol 2012; 194:6453-67. [PMID: 23002220 DOI: 10.1128/jb.01195-12] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Staphylococcus lugdunensis is the only coagulase-negative Staphylococcus species with a locus encoding iron-regulated surface determinant (Isd) proteins. In Staphylococcus aureus, the Isd proteins capture heme from hemoglobin and transfer it across the wall to a membrane-bound transporter, which delivers it into the cytoplasm, where heme oxygenases release iron. The Isd proteins of S. lugdunensis are expressed under iron-restricted conditions. We propose that S. lugdunensis IsdB and IsdC proteins perform the same functions as those of S. aureus. S. lugdunensis IsdB is the only hemoglobin receptor within the isd locus. It specifically binds human hemoglobin with a dissociation constant (K(d)) of 23 nM and transfers heme on IsdC. IsdB expression promotes bacterial growth in an iron-limited medium containing human hemoglobin but not mouse hemoglobin. This correlates with weak binding of IsdB to mouse hemoglobin in vitro. Unlike IsdB and IsdC, the proteins IsdJ and IsdK are not sorted to the cell wall in S. lugdunensis. In contrast, IsdJ expressed in S. aureus and Lactococcus lactis is anchored to peptidoglycan, suggesting that S. lugdunensis sortases may differ in signal recognition or could be defective. IsdJ and IsdK are present in the culture supernatant, suggesting that they could acquire heme from the external milieu. The IsdA protein of S. aureus protects bacteria from bactericidal lipids due to its hydrophilic C-terminal domain. IsdJ has a similar region and protected S. aureus and L. lactis as efficiently as IsdA but, possibly due to its location, was less effective in its natural host.
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35
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Tiedemann MT, Pinter TBJ, Stillman MJ. Insight into blocking heme transfer by exploiting molecular interactions in the core Isd heme transporters IsdA-NEAT, IsdC-NEAT, and IsdE of Staphylococcus aureus. Metallomics 2012; 4:751-60. [PMID: 22786442 DOI: 10.1039/c2mt20067h] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The pathogenic bacterium Staphylococcus aureus has adopted specialized mechanisms for scavenging iron from its host. The nine cell wall and membrane-associated iron regulated surface determinant (Isd) proteins (IsdH, IsdB, IsdA, IsdC, IsdDEF, IsdG and IsdI) allow Staphylococcus aureus to scavenge iron from the heme in hemoglobin and haptoglobin-hemoglobin. Of these, it is IsdE that chaperones the heme to the ATP binding cassette-type transmembrane transporter (IsdF). IsdH, IsdB, IsdA and IsdC contain at least one heme binding Near Transporter (NEAT) domain. Previous studies have shown that ferric heme is transferred unidirectionally in the sequence IsdA-NEAT (Tyr - proximal amino acid) → IsdC-NEAT (Tyr) → IsdE (His). IsdA-NEAT does not transfer heme directly to IsdE. In this paper we investigated PPIX transfer through the core cell wall proteins of the Isd system (IsdA-NEAT, IsdC-NEAT and IsdE) with FePPIX-dimethylester, and the metal substituted CoPPIX and MnPPIX using ESI-MS, UV-visible absorption and MCD spectroscopy. IsdA binds each of the rings but the subsequent transfer properties to IsdC-N or IsdE are not the same as found with heme. FePPIX-DME transfers from IsdA-N to IsdC-N but neither protein transfers the ring to IsdE. IsdA-N does not transfer CoPPIX to IsdC-N or IsdE. IsdA-N does transfer MnPPIX to both IsdC-N and IsdE. Significantly, it is possible that since CoPPIX and FePPIX-DME bind to IsdA-N, the lack of transfer to IsdC-N and subsequently to IsdE for CoPPIX could prove to be used as a potential disruption agent to the S. aureus heme transfer system and may identify a possible anti-microbial.
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Affiliation(s)
- Michael T Tiedemann
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada
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36
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Abstract
Haem is the major iron source for bacteria that develop in higher organisms. In these hosts, bacteria have to cope with nutritional immunity imposed by the host, since haem and iron are tightly bound to carrier and storage proteins. Siderophores were the first recognized fighters in the battle for iron between bacteria and host. They are non-proteinaceus organic molecules having an extremely high affinity for Fe(3+) and able to extract it from host proteins. Haemophores, that display functional analogy with siderophores, were more recently discovered. They are a class of secreted proteins with a high affinity for haem; they are able to extract haem from host haemoproteins and deliver it to specific receptors that internalize haem. In the past few years, a wealth of data has accumulated on haem acquisition systems that are dependent on surface exposed/secreted bacterial proteins. They promote haem transfer from its initial source (in most cases, a eukaryotic haem binding protein) to the transporter that carries out the membrane crossing step. Here we review recent discoveries in this field, with particular emphasis on similar and dissimilar mechanisms in haemophores and siderophores, from the initial host source to the binding protein/receptor at the cell surface.
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Affiliation(s)
- Cécile Wandersman
- Unité des Membranes Bactériennes, Institut Pasteur, Département de Microbiologie, 25-28, rue du Dr. Roux, 75724 Paris Cedex 15, France.
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37
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Tiedemann MT, Stillman MJ. Heme binding to the IsdE(M78A; H229A) double mutant: challenging unidirectional heme transfer in the iron-regulated surface determinant protein heme transfer pathway of Staphylococcus aureus. J Biol Inorg Chem 2012; 17:995-1007. [DOI: 10.1007/s00775-012-0914-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Accepted: 06/07/2012] [Indexed: 10/28/2022]
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Abe R, Caaveiro JMM, Kozuka-Hata H, Oyama M, Tsumoto K. Mapping ultra-weak protein-protein interactions between heme transporters of Staphylococcus aureus. J Biol Chem 2012; 287:16477-87. [PMID: 22427659 DOI: 10.1074/jbc.m112.346700] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Iron is an essential nutrient for the proliferation of Staphylococcus aureus during bacterial infections. The iron-regulated surface determinant (Isd) system of S. aureus transports and metabolizes iron porphyrin (heme) captured from the host organism. Transportation of heme across the thick cell wall of this bacterium requires multiple relay points. The mechanism by which heme is physically transferred between Isd transporters is largely unknown because of the transient nature of the interactions involved. Herein, we show that the IsdC transporter not only passes heme ligand to another class of Isd transporter, as previously known, but can also perform self-transfer reactions. IsdA shows a similar ability. A genetically encoded photoreactive probe was used to survey the regions of IsdC involved in self-dimerization. We propose an updated model that explicitly considers self-transfer reactions to explain heme delivery across the cell wall. An analogous photo-cross-linking strategy was employed to map transient interactions between IsdC and IsdE transporters. These experiments identified a key structural element involved in the rapid and specific transfer of heme from IsdC to IsdE. The resulting structural model was validated with a chimeric version of the homologous transporter IsdA. Overall, our results show that the ultra-weak interactions between Isd transporters are governed by bona fide protein structural motifs.
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Affiliation(s)
- Ryota Abe
- Department of Medical Genome Sciences, School of Frontier Sciences, University of Tokyo, Minato-ku, Tokyo 108-8639, Japan
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39
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Ekworomadu MT, Poor CB, Owens CP, Balderas MA, Fabian M, Olson JS, Murphy F, Balkabasi E, Honsa ES, He C, Goulding CW, Maresso AW. Differential function of lip residues in the mechanism and biology of an anthrax hemophore. PLoS Pathog 2012; 8:e1002559. [PMID: 22412371 PMCID: PMC3297588 DOI: 10.1371/journal.ppat.1002559] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Accepted: 01/16/2012] [Indexed: 11/19/2022] Open
Abstract
To replicate in mammalian hosts, bacterial pathogens must acquire iron. The majority of iron is coordinated to the protoporphyrin ring of heme, which is further bound to hemoglobin. Pathogenic bacteria utilize secreted hemophores to acquire heme from heme sources such as hemoglobin. Bacillus anthracis, the causative agent of anthrax disease, secretes two hemophores, IsdX1 and IsdX2, to acquire heme from host hemoglobin and enhance bacterial replication in iron-starved environments. Both proteins contain NEAr-iron Transporter (NEAT) domains, a conserved protein module that functions in heme acquisition in Gram-positive pathogens. Here, we report the structure of IsdX1, the first of a Gram-positive hemophore, with and without bound heme. Overall, IsdX1 forms an immunoglobin-like fold that contains, similar to other NEAT proteins, a 310-helix near the heme-binding site. Because the mechanistic function of this helix in NEAT proteins is not yet defined, we focused on the contribution of this region to hemophore and NEAT protein activity, both biochemically and biologically in cultured cells. Site-directed mutagenesis of amino acids in and adjacent to the helix identified residues important for heme and hemoglobin association, with some mutations affecting both properties and other mutations affecting only heme stabilization. IsdX1 with mutations that reduced the ability to associate with hemoglobin and bind heme failed to restore the growth of a hemophore-deficient strain of B. anthracis on hemoglobin as the sole iron source. These data indicate that not only is the 310-helix important for NEAT protein biology, but also that the processes of hemoglobin and heme binding can be both separate as well as coupled, the latter function being necessary for maximal heme-scavenging activity. These studies enhance our understanding of NEAT domain and hemophore function and set the stage for structure-based inhibitor design to block NEAT domain interaction with upstream ligands. Pathogenic bacteria need to acquire host iron to replicate during infection. Approximately 80% of mammalian iron is associated with a small molecule termed heme, most of which is bound to circulating hemoglobin and involved in O2 transport in red cells. Bacteria secrete proteins, termed hemophores, to acquire the heme from hemoglobin, a process thought to accelerate delivery of the heme to the bacterial surface for iron import into the cell. The mechanisms by which hemophores extract host heme from hemoglobin are not known. Here, we report that the IsdX1 hemophore from B. anthracis, the causative agent of anthrax disease, uses a conserved structural feature to link hemoglobin association with heme binding and extraction, thereby facilitating bacterial growth in low-iron environments. Such “molecular coupling” suggests that specific inhibition of the hemophore-hemoglobin interaction for this class of proteins may serve as a starting point for new anti-infective therapeutics aimed at short-circuiting iron uptake networks in bacterial pathogens.
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Affiliation(s)
- MarCia T. Ekworomadu
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Catherine B. Poor
- Department of Chemistry, University of Chicago, Chicago, Illinois, United States of America
| | - Cedric P. Owens
- Departments of Molecular Biology and Biochemistry, University of California-Irvine, Irvine, California, United States of America
| | - Miriam A. Balderas
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Marian Fabian
- Department of Biochemistry and Cell Biology, Rice University, Houston, Texas, United States of America
| | - John S. Olson
- Department of Biochemistry and Cell Biology, Rice University, Houston, Texas, United States of America
| | - Frank Murphy
- Northeastern Collaborative Access Team, Argonne National Laboratory, Argonne, Illinois, United States of America
| | - Erol Balkabasi
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Erin S. Honsa
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Chuan He
- Department of Chemistry, University of Chicago, Chicago, Illinois, United States of America
| | - Celia W. Goulding
- Departments of Molecular Biology and Biochemistry, University of California-Irvine, Irvine, California, United States of America
| | - Anthony W. Maresso
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America
- * E-mail:
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40
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Smith AD, Wilks A. Extracellular heme uptake and the challenges of bacterial cell membranes. CURRENT TOPICS IN MEMBRANES 2012; 69:359-92. [PMID: 23046657 PMCID: PMC3731948 DOI: 10.1016/b978-0-12-394390-3.00013-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In bacteria, the fine balance of maintaining adequate iron levels while preventing the deleterious effects of excess iron has led to the evolution of sophisticated cellular mechanisms to obtain, store, and regulate iron. Iron uptake provides a significant challenge given its limited bioavailability and need to be transported across the bacterial cell wall and membranes. Pathogenic bacteria have circumvented the iron-availability issue by utilizing the hosts' heme-containing proteins as a source of iron. Once internalized, iron is liberated from the porphyrin enzymatically for cellular processes within the bacterial cell. Heme, a lipophilic and toxic molecule, poses a significant challenge in terms of transport given its chemical reactivity. As such, pathogenic bacteria have evolved sophisticated membrane transporters to coordinate, sequester, and transport heme. Recent advances in the biochemical and structural characterization of the membrane-bound heme transport proteins are discussed in the context of ligand coordination, protein-protein interaction, and heme transfer.
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Affiliation(s)
- Aaron D. Smith
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, USA
| | - Angela Wilks
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, USA
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