1
|
Ray S, Gaudet R. Structures and coordination chemistry of transporters involved in manganese and iron homeostasis. Biochem Soc Trans 2023; 51:897-923. [PMID: 37283482 PMCID: PMC10330786 DOI: 10.1042/bst20210699] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 05/23/2023] [Accepted: 05/25/2023] [Indexed: 06/08/2023]
Abstract
A repertoire of transporters plays a crucial role in maintaining homeostasis of biologically essential transition metals, manganese, and iron, thus ensuring cell viability. Elucidating the structure and function of many of these transporters has provided substantial understanding into how these proteins help maintain the optimal cellular concentrations of these metals. In particular, recent high-resolution structures of several transporters bound to different metals enable an examination of how the coordination chemistry of metal ion-protein complexes can help us understand metal selectivity and specificity. In this review, we first provide a comprehensive list of both specific and broad-based transporters that contribute to cellular homeostasis of manganese (Mn2+) and iron (Fe2+ and Fe3+) in bacteria, plants, fungi, and animals. Furthermore, we explore the metal-binding sites of the available high-resolution metal-bound transporter structures (Nramps, ABC transporters, P-type ATPase) and provide a detailed analysis of their coordination spheres (ligands, bond lengths, bond angles, and overall geometry and coordination number). Combining this information with the measured binding affinity of the transporters towards different metals sheds light into the molecular basis of substrate selectivity and transport. Moreover, comparison of the transporters with some metal scavenging and storage proteins, which bind metal with high affinity, reveal how the coordination geometry and affinity trends reflect the biological role of individual proteins involved in the homeostasis of these essential transition metals.
Collapse
Affiliation(s)
- Shamayeeta Ray
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, U.S.A
| | - Rachelle Gaudet
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, U.S.A
| |
Collapse
|
2
|
Li F, Huang K, Wang J, Yuan K, Yang Y, Liu Y, Zhou X, Kong K, Yang T, He J, Liu C, Ao H, Liu F, Liu Q, Tang T, Yang S. A dual functional Ti-Ga alloy: inhibiting biofilm formation and osteoclastogenesis differentiation via disturbing iron metabolism. Biomater Res 2023; 27:24. [PMID: 36978196 PMCID: PMC10053110 DOI: 10.1186/s40824-023-00362-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2022] [Accepted: 03/05/2023] [Indexed: 03/30/2023] Open
Abstract
BACKGROUND Although biomedical implants have been widely used in orthopedic treatments, two major clinical challenges remain to be solved, one is the bacterial infection resulting in biofilm formation, and the other is aseptic loosening during implantation due to over-activated osteoclastogenesis. These factors can cause many clinical issues and even lead to implant failure. Thus, it is necessary to endow implants with antibiofilm and aseptic loosening-prevention properties, to facilitate the integration between implants and bone tissues for successful implantation. To achieve this goal, this study aimed to develop a biocompatible titanium alloy with antibiofilm and anti-aseptic loosening dual function by utilizing gallium (Ga) as a component. METHODS A series of Ti-Ga alloys were prepared. We examined the Ga content, Ga distribution, hardness, tensile strength, biocompatibility, and anti-biofilm performance in vitro and in vivo. We also explored how Ga3+ ions inhibited the biofilm formation of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) and osteoclast differentiation. RESULTS The alloy exhibited outstanding antibiofilm properties against both S. aureus and E. coli in vitro and decent antibiofilm performance against S. aureus in vivo. The proteomics results demonstrated that Ga3+ ions could disturb the bacterial Fe metabolism of both S. aureus and E. coli, inhibiting bacterial biofilm formation. In addition, Ti-Ga alloys could inhibit receptor activator of nuclear factor-κB ligand (RANKL)-dependent osteoclast differentiation and function by targeting iron metabolism, then suppressing the activation of the NF-κB signaling pathway, thus, showing their potential to prevent aseptic loosening. CONCLUSION This study provides an advanced Ti-Ga alloy that can be used as a promising orthopedic implant raw material for various clinical scenarios. This work also revealed that iron metabolism is the common target of Ga3+ ions to inhibit biofilm formation and osteoclast differentiation.
Collapse
Affiliation(s)
- Fupeng Li
- Department of Orthopaedic Surgery, Shanghai Ninth People's Hospital, Shanghai Key Laboratory of Orthopaedic Implants, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
| | - Kai Huang
- Department of Orthopaedic Surgery, Shanghai Ninth People's Hospital, Shanghai Key Laboratory of Orthopaedic Implants, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China.
| | - Jinbing Wang
- Department of Oral and Maxillofacial-Head and Neck Oncology, Shanghai Ninth People's Hospital, College of Stomatology, National Center for Stomatology, National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai Research Institute of Stomatology, Shanghai, 200011, China
| | - Kai Yuan
- Department of Orthopaedic Surgery, Shanghai Ninth People's Hospital, Shanghai Key Laboratory of Orthopaedic Implants, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
| | - Yiqi Yang
- Department of Orthopaedic Surgery, Shanghai Ninth People's Hospital, Shanghai Key Laboratory of Orthopaedic Implants, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
| | - Yihao Liu
- Department of Orthopaedic Surgery, Shanghai Ninth People's Hospital, Shanghai Key Laboratory of Orthopaedic Implants, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
| | - Xianhao Zhou
- Department of Orthopaedic Surgery, Shanghai Ninth People's Hospital, Shanghai Key Laboratory of Orthopaedic Implants, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
| | - Keyu Kong
- Department of Orthopaedic Surgery, Shanghai Ninth People's Hospital, Shanghai Key Laboratory of Orthopaedic Implants, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
| | - Tao Yang
- Department of Materials Science and Engineering, Hong Kong Institute for Advanced Study, College of Science and Engineering, City University of Hong Kong, Hong Kong, China
| | - Jian He
- M-Duke Medical Technology (Shanghai) Co., Ltd, Shanghai, Shanghai, China
| | - Chunjie Liu
- M-Duke Medical Technology (Shanghai) Co., Ltd, Shanghai, Shanghai, China
| | - Haiyong Ao
- Jiangxi Key Laboratory of Nanobiomaterials & School of Materials Science and Engineering, East China Jiaotong University, Nanchang, 330000, China
| | - Fengxiang Liu
- Department of Orthopaedic Surgery, Shanghai Ninth People's Hospital, Shanghai Key Laboratory of Orthopaedic Implants, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China.
| | - Qian Liu
- Department of laboratory medicine, Ren Ji Hospital, Shanghai Jiao tong university school of medicine, Shanghai, 200127, China.
| | - Tingting Tang
- Department of Orthopaedic Surgery, Shanghai Ninth People's Hospital, Shanghai Key Laboratory of Orthopaedic Implants, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China.
| | - Shengbing Yang
- Department of Orthopaedic Surgery, Shanghai Ninth People's Hospital, Shanghai Key Laboratory of Orthopaedic Implants, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China.
| |
Collapse
|
3
|
Mohammad M, Ali A, Nguyen MT, Götz F, Pullerits R, Jin T. Staphylococcus aureus lipoproteins in infectious diseases. Front Microbiol 2022; 13:1006765. [PMID: 36262324 PMCID: PMC9574248 DOI: 10.3389/fmicb.2022.1006765] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 09/06/2022] [Indexed: 11/13/2022] Open
Abstract
Infections with the Gram-positive bacterial pathogen Staphylococcus aureus remain a major challenge for the healthcare system and demand new treatment options. The increasing antibiotic resistance of S. aureus poses additional challenges, consequently inflicting a huge strain in the society due to enormous healthcare costs. S. aureus expresses multiple molecules, including bacterial lipoproteins (Lpps), which play a role not only in immune response but also in disease pathogenesis. S. aureus Lpps, the predominant ligands of TLR2, are important for bacterial survival as they maintain the metabolic activity of the bacteria. Moreover, Lpps possess many diverse properties that are of vital importance for the bacteria. They also contribute to host cell invasion but so far their role in different staphylococcal infections has not been fully defined. In this review, we summarize the current knowledge about S. aureus Lpps and their distinct roles in various infectious disease animal models, such as septic arthritis, sepsis, and skin and soft tissue infections. The molecular and cellular response of the host to S. aureus Lpp exposure is also a primary focus.
Collapse
Affiliation(s)
- Majd Mohammad
- Department of Rheumatology and Inflammation Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- *Correspondence: Majd Mohammad,
| | - Abukar Ali
- Department of Rheumatology and Inflammation Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Minh-Thu Nguyen
- Section of Medical and Geographical Infectiology, Institute of Medical Microbiology, University Hospital of Münster, Münster, Germany
| | - Friedrich Götz
- Department of Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, Germany
| | - Rille Pullerits
- Department of Rheumatology and Inflammation Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Department of Clinical Immunology and Transfusion Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Tao Jin
- Department of Rheumatology and Inflammation Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Department of Rheumatology, Sahlgrenska University Hospital, Gothenburg, Sweden
| |
Collapse
|
4
|
Mixed Populations and Co-Infection: Pseudomonas aeruginosa and Staphylococcus aureus. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1386:397-424. [DOI: 10.1007/978-3-031-08491-1_15] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
|
5
|
Overview of structurally homologous flavoprotein oxidoreductases containing the low M r thioredoxin reductase-like fold - A functionally diverse group. Arch Biochem Biophys 2021; 702:108826. [PMID: 33684359 DOI: 10.1016/j.abb.2021.108826] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 02/23/2021] [Accepted: 02/27/2021] [Indexed: 01/12/2023]
Abstract
Structural studies show that enzymes have a limited number of unique folds, although structurally related enzymes have evolved to perform a large variety of functions. In this review, we have focused on enzymes containing the low molecular weight thioredoxin reductase (low Mr TrxR) fold. This fold consists of two domains, both containing a three-layer ββα sandwich Rossmann-like fold, serving as flavin adenine dinucleotide (FAD) and, in most cases, pyridine nucleotide (NAD(P)H) binding-domains. Based on a search of the Protein Data Bank for all published structures containing the low Mr TrxR-like fold, we here present a comprehensive overview of enzymes with this structural architecture. These range from TrxR-like ferredoxin/flavodoxin NAD(P)+ oxidoreductases, through glutathione reductase, to NADH peroxidase. Some enzymes are solely composed of the low Mr TrxR-like fold, while others contain one or two additional domains. In this review, we give a detailed description of selected enzymes containing only the low Mr TrxR-like fold, however, catalyzing a diversity of chemical reactions. Our overview of this structurally similar, yet functionally distinct group of flavoprotein oxidoreductases highlights the fascinating and increasing number of studies describing the diversity among these enzymes, especially during the last decade(s).
Collapse
|
6
|
Jochim A, Adolf L, Belikova D, Schilling NA, Setyawati I, Chin D, Meyers S, Verhamme P, Heinrichs DE, Slotboom DJ, Heilbronner S. An ECF-type transporter scavenges heme to overcome iron-limitation in Staphylococcus lugdunensis. eLife 2020; 9:e57322. [PMID: 32515736 PMCID: PMC7299338 DOI: 10.7554/elife.57322] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 06/09/2020] [Indexed: 01/03/2023] Open
Abstract
Energy-coupling factor type transporters (ECF) represent trace nutrient acquisition systems. Substrate binding components of ECF-transporters are membrane proteins with extraordinary affinity, allowing them to scavenge trace amounts of ligand. A number of molecules have been described as substrates of ECF-transporters, but an involvement in iron-acquisition is unknown. Host-induced iron limitation during infection represents an effective mechanism to limit bacterial proliferation. We identified the iron-regulated ECF-transporter Lha in the opportunistic bacterial pathogen Staphylococcus lugdunensis and show that the transporter is specific for heme. The recombinant substrate-specific subunit LhaS accepted heme from diverse host-derived hemoproteins. Using isogenic mutants and recombinant expression of Lha, we demonstrate that its function is independent of the canonical heme acquisition system Isd and allows proliferation on human cells as sources of nutrient iron. Our findings reveal a unique strategy of nutritional heme acquisition and provide the first example of an ECF-transporter involved in overcoming host-induced nutritional limitation.
Collapse
Affiliation(s)
- Angelika Jochim
- Interfaculty Institute of Microbiology and Infection Medicine, Department of Infection Biology, University of TübingenTübingenGermany
| | - Lea Adolf
- Interfaculty Institute of Microbiology and Infection Medicine, Department of Infection Biology, University of TübingenTübingenGermany
| | - Darya Belikova
- Interfaculty Institute of Microbiology and Infection Medicine, Department of Infection Biology, University of TübingenTübingenGermany
| | | | - Inda Setyawati
- Groningen Biomolecular Sciences and Biotechnology Institute, University of GroningenGroningenNetherlands
| | - Denny Chin
- Department of Microbiology and Immunology, University of Western OntarioLondonCanada
| | | | | | - David E Heinrichs
- Department of Microbiology and Immunology, University of Western OntarioLondonCanada
| | - Dirk J Slotboom
- Groningen Biomolecular Sciences and Biotechnology Institute, University of GroningenGroningenNetherlands
| | - Simon Heilbronner
- Interfaculty Institute of Microbiology and Infection Medicine, Department of Infection Biology, University of TübingenTübingenGermany
- German Centre for Infection Research (DZIF), Partner Site TübingenTübingenGermany
- (DFG) Cluster of Excellence EXC 2124 Controlling Microbes to Fight InfectionsTübingenGermany
| |
Collapse
|
7
|
Marchetti M, De Bei O, Bettati S, Campanini B, Kovachka S, Gianquinto E, Spyrakis F, Ronda L. Iron Metabolism at the Interface between Host and Pathogen: From Nutritional Immunity to Antibacterial Development. Int J Mol Sci 2020; 21:E2145. [PMID: 32245010 PMCID: PMC7139808 DOI: 10.3390/ijms21062145] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 03/16/2020] [Accepted: 03/17/2020] [Indexed: 02/08/2023] Open
Abstract
Nutritional immunity is a form of innate immunity widespread in both vertebrates and invertebrates. The term refers to a rich repertoire of mechanisms set up by the host to inhibit bacterial proliferation by sequestering trace minerals (mainly iron, but also zinc and manganese). This strategy, selected by evolution, represents an effective front-line defense against pathogens and has thus inspired the exploitation of iron restriction in the development of innovative antimicrobials or enhancers of antimicrobial therapy. This review focuses on the mechanisms of nutritional immunity, the strategies adopted by opportunistic human pathogen Staphylococcus aureus to circumvent it, and the impact of deletion mutants on the fitness, infectivity, and persistence inside the host. This information finally converges in an overview of the current development of inhibitors targeting the different stages of iron uptake, an as-yet unexploited target in the field of antistaphylococcal drug discovery.
Collapse
Affiliation(s)
- Marialaura Marchetti
- Interdepartmental Center Biopharmanet-TEC, University of Parma, 43124 Parma, Italy; (M.M.); (S.B.)
| | - Omar De Bei
- Department of Food and Drug, University of Parma, 43124 Parma, Italy; (O.D.B.); (B.C.)
| | - Stefano Bettati
- Interdepartmental Center Biopharmanet-TEC, University of Parma, 43124 Parma, Italy; (M.M.); (S.B.)
- Department of Medicine and Surgery, University of Parma, 43126 Parma, Italy
- Institute of Biophysics, National Research Council, 56124 Pisa, Italy
- National Institute of Biostructures and Biosystems, 00136 Rome, Italy
| | - Barbara Campanini
- Department of Food and Drug, University of Parma, 43124 Parma, Italy; (O.D.B.); (B.C.)
| | - Sandra Kovachka
- Department of Drug Science and Technology, University of Turin, 10125 Turin, Italy; (S.K.); (E.G.); (F.S.)
| | - Eleonora Gianquinto
- Department of Drug Science and Technology, University of Turin, 10125 Turin, Italy; (S.K.); (E.G.); (F.S.)
| | - Francesca Spyrakis
- Department of Drug Science and Technology, University of Turin, 10125 Turin, Italy; (S.K.); (E.G.); (F.S.)
| | - Luca Ronda
- Interdepartmental Center Biopharmanet-TEC, University of Parma, 43124 Parma, Italy; (M.M.); (S.B.)
- Department of Medicine and Surgery, University of Parma, 43126 Parma, Italy
- Institute of Biophysics, National Research Council, 56124 Pisa, Italy
| |
Collapse
|
8
|
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.
Collapse
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.
| |
Collapse
|
9
|
Wang H, Kraus F, Popella P, Baykal A, Guttroff C, François P, Sass P, Plietker B, Götz F. The Polycyclic Polyprenylated Acylphloroglucinol Antibiotic PPAP 23 Targets the Membrane and Iron Metabolism in Staphylococcus aureus. Front Microbiol 2019; 10:14. [PMID: 30728811 PMCID: PMC6352742 DOI: 10.3389/fmicb.2019.00014] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 01/07/2019] [Indexed: 11/13/2022] Open
Abstract
Recently, a series of endo-type B polycyclic polyprenylated acylphloroglucinols (PPAP) derivatives with high antimicrobial activities were chemically synthesized. One of the derivatives, PPAP 23, which showed high antimicrobial activity and low cytotoxicity, was chosen for further investigation of its bactericidal profiles and mode of action. PPAP 23 showed a better efficacy in killing methicillin resistant Staphylococcus aureus (MRSA) and decreasing the metabolic activity of 5-day-old biofilm cells than vancomycin. Moreover, S. aureus did not appear to develop resistance against PPAP 23. The antimicrobial mechanism of PPAP 23 was investigated by RNA-seq combined with phenotypic and biochemical approaches. RNA-seq suggested that PPAP 23 signaled iron overload to the bacterial cells because genes involved in iron transport were downregulated and iron storage gene was upregulated by PPAP 23. PPAP 23 affected the membrane integrity but did not induce pore formation; it inhibited bacterial respiration. PPAP 23 preferentially inhibited Fe–S cluster enzymes; it has a mild iron chelating activity and supplementation of exogenous iron attenuated its antimicrobial activity. PPAP 23 was more effective in inhibiting the growth of S. aureus under iron-restricted condition. The crystal structure of a benzylated analog of PPAP 23 showed a highly defined octahedral coordination of three PPAP ligands around a Fe (3+) core. This suggests that PPAPs are generally capable of iron chelation and are able to form defined stable complexes. PPAP 23 was found to induce reactive oxygen species (ROS) and oxidative stress. Fluorescence microscopic analysis showed that PPAP 23 caused an enlargement of the bacterial cells, perturbed the membrane, and dislocated the nucleoid. Taken together, we postulate that PPAP 23 interacts with the cytoplasmic membrane with its hydrophobic pocket and interferes with the iron metabolism to exert its antimicrobial activity in Staphylococcus aureus.
Collapse
Affiliation(s)
- Huanhuan Wang
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Tübingen, Germany
| | - Frank Kraus
- Institut für Organische Chemie, Universität Stuttgart, Stuttgart, Germany
| | - Peter Popella
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Tübingen, Germany
| | - Aslihan Baykal
- Institut für Organische Chemie, Universität Stuttgart, Stuttgart, Germany
| | - Claudia Guttroff
- Institut für Organische Chemie, Universität Stuttgart, Stuttgart, Germany
| | - Patrice François
- Genomic Research Laboratory, Division of Infectious Diseases, Geneva University Hospital, Geneva, Switzerland
| | - Peter Sass
- Microbial Bioactive Compounds, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Tübingen, Germany
| | - Bernd Plietker
- Institut für Organische Chemie, Universität Stuttgart, Stuttgart, Germany
| | - Friedrich Götz
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Tübingen, Germany
| |
Collapse
|
10
|
Abstract
During infection, bacteria must steal metals, including iron, from the host tissue. Therefore, pathogenic bacteria have evolved metal acquisition systems to overcome the elaborate processes mammals use to withhold metal from pathogens. Staphylococcus aureus uses IsdB, a hemoglobin receptor, to thieve iron-containing heme from hemoglobin within human blood. We find evidence that primate hemoglobin has undergone rapid evolution at protein surfaces contacted by IsdB. Additionally, variation in the hemoglobin sequences among primates, or variation in IsdB of related staphylococci, reduces bacterial hemoglobin capture. Together, these data suggest that S. aureus has evolved to recognize human hemoglobin in the face of rapid evolution at the IsdB binding interface, consistent with repeated evolutionary conflicts in the battle for iron during host-pathogen interactions. Metals are a limiting resource for pathogenic bacteria and must be scavenged from host proteins. Hemoglobin provides the most abundant source of iron in the human body and is required by several pathogens to cause invasive disease. However, the consequences of hemoglobin evolution for bacterial nutrient acquisition remain unclear. Here we show that the α- and β-globin genes exhibit strikingly parallel signatures of adaptive evolution across simian primates. Rapidly evolving sites in hemoglobin correspond to binding interfaces of IsdB, a bacterial hemoglobin receptor harbored by pathogenic Staphylococcus aureus. Using an evolution-guided experimental approach, we demonstrate that the divergence between primates and staphylococcal isolates governs hemoglobin recognition and bacterial growth. The reintroduction of putative adaptive mutations in α- or β-globin proteins was sufficient to impair S. aureus binding, providing a mechanism for the evolution of disease resistance. These findings suggest that bacterial hemoprotein capture has driven repeated evolutionary conflicts with hemoglobin during primate descent.
Collapse
|
11
|
Structural properties of a haemophore facilitate targeted elimination of the pathogen Porphyromonas gingivalis. Nat Commun 2018; 9:4097. [PMID: 30291238 PMCID: PMC6173696 DOI: 10.1038/s41467-018-06470-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 09/05/2018] [Indexed: 12/22/2022] Open
Abstract
Porphyromonas gingivalis is a keystone bacterial pathogen of chronic periodontitis. P. gingivalis is unable to synthesise the porphyrin macrocycle and relies on exogenous porphyrin, including haem or haem biosynthesis intermediates from host sources. We show that under the iron-limited conditions prevailing in tissue environments, P. gingivalis expresses a haemophore-like protein, HusA, to mediate the uptake of essential porphyrin and support pathogen survival within epithelial cells. The structure of HusA, together with titration studies, mutagenesis and in silico docking, show that haem binds in a hydrophobic groove on the α-helical structure without the typical iron coordination seen in other haemophores. This mode of interaction allows HusA to bind to a variety of abiotic and metal-free porphyrins with higher affinities than to haem. We exploit this unusual porphyrin-binding activity of HusA to target a prototypic deuteroporphyrin-metronidazole conjugate with restricted antimicrobial specificity in a Trojan horse strategy that effectively kills intracellular P. gingivalis.
Collapse
|
12
|
Bartual SG, Alcorlo M, Martínez-Caballero S, Molina R, Hermoso JA. Three-dimensional structures of Lipoproteins from Streptococcus pneumoniae and Staphylococcus aureus. Int J Med Microbiol 2018; 308:692-704. [DOI: 10.1016/j.ijmm.2017.10.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 10/21/2017] [Indexed: 01/01/2023] Open
|
13
|
Bowden CFM, Chan ACK, Li EJW, Arrieta AL, Eltis LD, Murphy MEP. Structure-function analyses reveal key features in Staphylococcus aureus IsdB-associated unfolding of the heme-binding pocket of human hemoglobin. J Biol Chem 2017; 293:177-190. [PMID: 29109153 DOI: 10.1074/jbc.m117.806562] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 10/19/2017] [Indexed: 11/06/2022] Open
Abstract
IsdB is a receptor on the surface of the bacterial pathogen Staphylococcus aureus that extracts heme from hemoglobin (Hb) to enable growth on Hb as a sole iron source. IsdB is critically important both for in vitro growth on Hb and in infection models and is also highly up-regulated in blood, serum, and tissue infection models, indicating a key role of this receptor in bacterial virulence. However, structural information for IsdB is limited. We present here a crystal structure of a complex between human Hb and IsdB. In this complex, the α subunits of Hb are refolded with the heme displaced to the interface with IsdB. We also observe that atypical residues of Hb, His58 and His89 of αHb, coordinate to the heme iron, which is poised for transfer into the heme-binding pocket of IsdB. Moreover, the porphyrin ring interacts with IsdB residues Tyr440 and Tyr444 Previously, Tyr440 was observed to coordinate heme iron in an IsdB·heme complex structure. A Y440F/Y444F IsdB variant we produced was defective in heme transfer yet formed a stable complex with Hb (Kd = 6 ± 2 μm) in solution with spectroscopic features of the bis-His species observed in the crystal structure. Haptoglobin binds to a distinct site on Hb to inhibit heme transfer to IsdB and growth of S. aureus, and a ternary complex of IsdB·Hb·Hp was observed. We propose a model for IsdB heme transfer from Hb that involves unfolding of Hb and heme iron ligand exchange.
Collapse
Affiliation(s)
- Catherine F M Bowden
- Department of Microbiology and Immunology, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Anson C K Chan
- Department of Microbiology and Immunology, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Emily J W Li
- Department of Microbiology and Immunology, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Angelé L Arrieta
- Department of Microbiology and Immunology, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Lindsay D Eltis
- Department of Microbiology and Immunology, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Michael E P Murphy
- Department of Microbiology and Immunology, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
| |
Collapse
|
14
|
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.
Collapse
|
15
|
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.
Collapse
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;
| |
Collapse
|
16
|
Brewitz HH, Hagelueken G, Imhof D. Structural and functional diversity of transient heme binding to bacterial proteins. Biochim Biophys Acta Gen Subj 2017; 1861:683-697. [DOI: 10.1016/j.bbagen.2016.12.021] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 12/15/2016] [Accepted: 12/20/2016] [Indexed: 11/27/2022]
|
17
|
Diverse structural approaches to haem appropriation by pathogenic bacteria. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2017; 1865:422-433. [PMID: 28130069 DOI: 10.1016/j.bbapap.2017.01.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 01/16/2017] [Accepted: 01/23/2017] [Indexed: 11/24/2022]
Abstract
The critical need for iron presents a challenge for pathogenic bacteria that must survive in an environment bereft of accessible iron due to a natural low bioavailability and their host's nutritional immunity. Appropriating haem, either direct from host haemoproteins or by secreting haem-scavenging haemophores, is one way pathogenic bacteria can overcome this challenge. After capturing their target, haem appropriation systems must remove haem from a high-affinity binding site (on the host haemoprotein or bacterial haemophore) and transfer it to a binding site of lower affinity on a bacterial receptor. Structural information is now available to show how, using a combination of induced structural changes and steric clashes, bacteria are able to extract haem from haemophores, haemopexin and haemoglobin. This review focuses on structural descriptions of these bacterial haem acquisition systems, summarising how they bind haem and their target haemoproteins with particularly emphasis on the mechanism of haem extraction.
Collapse
|
18
|
Shahmirzadi SV, Nguyen MT, Götz F. Evaluation of Staphylococcus aureus Lipoproteins: Role in Nutritional Acquisition and Pathogenicity. Front Microbiol 2016; 7:1404. [PMID: 27679612 PMCID: PMC5020093 DOI: 10.3389/fmicb.2016.01404] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 08/24/2016] [Indexed: 01/22/2023] Open
Abstract
Bacterial lipoproteins (Lpp) represent a major class of membrane proteins. They are distinguished by a lipid moiety at the N-terminus by which they are anchored either in the outer leaflet of the cytoplasmic membrane or, in Gram-negative bacteria, also in the inner leaflet of the outer membrane. In Gram-positive bacteria Lpp significantly contribute to nutrient transport, Toll-like receptor 2 activation and pathogenicity. Here we examine the Lpp of Staphylococcus aureus USA300, as a prototype for a multiple antibiotic resistant and community-acquired pathogen that is rapidly spreading worldwide. The compiled Lpp were grouped according to the postulated function and dissemination of homologs in the genus Staphylococcus and beyond. Based on this evaluation we also point out Lpp as promising vaccine candidates.
Collapse
Affiliation(s)
- Shideh V Shahmirzadi
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen Tübingen, Germany
| | - Minh-Thu Nguyen
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen Tübingen, Germany
| | - Friedrich Götz
- Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen Tübingen, Germany
| |
Collapse
|
19
|
Vu CH, Kolata J, Stentzel S, Beyer A, Gesell Salazar M, Steil L, Pané-Farré J, Rühmling V, Engelmann S, Götz F, van Dijl JM, Hecker M, Mäder U, Schmidt F, Völker U, Bröker BM. Adaptive immune response to lipoproteins of Staphylococcus aureus in healthy subjects. Proteomics 2016; 16:2667-2677. [PMID: 27324828 PMCID: PMC5096053 DOI: 10.1002/pmic.201600151] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 05/31/2016] [Accepted: 06/16/2016] [Indexed: 01/03/2023]
Abstract
Staphylococcus aureus is a frequent commensal but also a dangerous pathogen, causing many forms of infection ranging from mild to life‐threatening conditions. Among its virulence factors are lipoproteins, which are anchored in the bacterial cell membrane. Lipoproteins perform various functions in colonization, immune evasion, and immunomodulation. These proteins are potent activators of innate immune receptors termed Toll‐like receptors 2 and 6. This study addressed the specific B‐cell and T‐cell responses directed to lipoproteins in human S. aureus carriers and non‐carriers. 2D immune proteomics and ELISA approaches revealed that titers of antibodies (IgG) binding to S. aureus lipoproteins were very low. Proliferation assays and cytokine profiling data showed only subtle responses of T cells; some lipoproteins did not elicit proliferation. Hence, the robust activation of the innate immune system by S. aureus lipoproteins does not translate into a strong adaptive immune response. Reasons for this may include inaccessibility of lipoproteins for B cells as well as ineffective processing and presentation of the antigens to T cells.
Collapse
Affiliation(s)
- Chi Hai Vu
- Institute of Immunology and Transfusion Medicine, University Medicine Greifswald, Greifswald, Germany
| | - Julia Kolata
- Institute of Immunology and Transfusion Medicine, University Medicine Greifswald, Greifswald, Germany.,Medical Microbiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Sebastian Stentzel
- Institute of Immunology and Transfusion Medicine, University Medicine Greifswald, Greifswald, Germany
| | - Anica Beyer
- Institute of Microbiology, University of Greifswald, Greifswald, Germany
| | - Manuela Gesell Salazar
- Interfaculty Institute of Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Leif Steil
- Interfaculty Institute of Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Jan Pané-Farré
- Institute of Microbiology, University of Greifswald, Greifswald, Germany
| | - Vanessa Rühmling
- Institute of Microbiology, University of Greifswald, Greifswald, Germany
| | - Susanne Engelmann
- Institute of Microbiology, University of Greifswald, Greifswald, Germany.,Helmholtz Center for Infection Research, Microbial Proteomics, Braunschweig, Germany.,Institute for Microbiology, University of Braunschweig, Braunschweig, Germany
| | - Friedrich Götz
- Department of Microbial Genetics, University of Tübingen, Tübingen, Germany
| | - Jan Maarten van Dijl
- Department of Medical Microbiology, University Medical Center Groningen, Groningen, The Netherlands
| | - Michael Hecker
- Institute of Microbiology, University of Greifswald, Greifswald, Germany
| | - Ulrike Mäder
- Interfaculty Institute of Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Frank Schmidt
- Interfaculty Institute of Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Uwe Völker
- Interfaculty Institute of Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Barbara M Bröker
- Institute of Immunology and Transfusion Medicine, University Medicine Greifswald, Greifswald, Germany.
| |
Collapse
|
20
|
Structural Characterization of Heme Environmental Mutants of CgHmuT that Shuttles Heme Molecules to Heme Transporters. Int J Mol Sci 2016; 17:ijms17060829. [PMID: 27240352 PMCID: PMC4926363 DOI: 10.3390/ijms17060829] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 05/19/2016] [Accepted: 05/24/2016] [Indexed: 01/19/2023] Open
Abstract
Corynebacteria contain a heme uptake system encoded in hmuTUV genes, in which HmuT protein acts as a heme binding protein to transport heme to the cognate transporter HmuUV. The crystal structure of HmuT from Corynebacterium glutamicum (CgHmuT) reveals that heme is accommodated in the central cleft with His141 and Tyr240 as the axial ligands and that Tyr240 forms a hydrogen bond with Arg242. In this work, the crystal structures of H141A, Y240A, and R242A mutants were determined to understand the role of these residues for the heme binding of CgHmuT. Overall and heme environmental structures of these mutants were similar to those of the wild type, suggesting that there is little conformational change in the heme-binding cleft during heme transport reaction with binding and the dissociation of heme. A loss of one axial ligand or the hydrogen bonding interaction with Tyr240 resulted in an increase in the redox potential of the heme for CgHmuT to be reduced by dithionite, though the wild type was not reduced under physiological conditions. These results suggest that the heme environmental structure stabilizes the ferric heme binding in CgHmuT, which will be responsible for efficient heme uptake under aerobic conditions where Corynebacteria grow.
Collapse
|
21
|
Akbas N, Draganova EB, Block DR, Sook BR, Chan YF, Zhuo J, Eichenbaum Z, Rodgers KR, Dixon DW. Heme-bound SiaA from Streptococcus pyogenes: Effects of mutations and oxidation state on protein stability. J Inorg Biochem 2016; 158:99-109. [PMID: 26746808 PMCID: PMC4943329 DOI: 10.1016/j.jinorgbio.2015.10.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 10/01/2015] [Accepted: 10/28/2015] [Indexed: 11/30/2022]
Abstract
The protein SiaA (HtsA) is part of a heme uptake pathway in Streptococcus pyogenes. In this report, we present the heme binding of the alanine mutants of the axial histidine (H229A) and methionine (M79A) ligands, as well as a lysine (K61A) and cysteine (C58A) located near the heme propionates (based on homology modeling) and a control mutant (C47A). pH titrations gave pKa values ranging from 9.0 to 9.5, close to the value of 9.7 for WT SiaA. Resonance Raman spectra of the mutants suggested that the ferric heme environment may be distinct from the wild-type; spectra of the ferrous states were similar. The midpoint reduction potential of the K61A mutant was determined by spectroelectrochemical titration to be 61±3mV vs. SHE, similar to the wild-type protein (68±3mV). The addition of guanidine hydrochloride showed two processes for protein denaturation, consistent with heme loss from protein forms differing by the orientation of the heme in the binding pocket (the half-life for the slower process ranged from less than half a day to two days). The ease of protein unfolding was related to the strength of interaction of the residues with the heme. We hypothesize that kinetically facile but only partial unfolding, followed by a very slow approach to the completely unfolded state, may be a fundamental attribute of heme trafficking proteins. Small motions to release/transfer the heme accompanied by resistance to extensive unfolding may preserve the three dimensional form of the protein for further uptake and release.
Collapse
Affiliation(s)
- Neval Akbas
- Department of Chemistry, Georgia State University, Atlanta, GA 30302-3965, USA
| | | | - Darci R Block
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA
| | - Brian R Sook
- Department of Chemistry, Georgia State University, Atlanta, GA 30302-3965, USA
| | - Yau Fong Chan
- Department of Chemistry, Georgia State University, Atlanta, GA 30302-3965, USA
| | - Joy Zhuo
- Department of Chemistry, Georgia State University, Atlanta, GA 30302-3965, USA
| | - Zehava Eichenbaum
- Department of Biology, Georgia State University, Atlanta, GA 30303, USA
| | - Kenton R Rodgers
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA
| | - Dabney W Dixon
- Department of Chemistry, Georgia State University, Atlanta, GA 30302-3965, USA.
| |
Collapse
|
22
|
Tyrrell J, Callaghan M. Iron acquisition in the cystic fibrosis lung and potential for novel therapeutic strategies. MICROBIOLOGY-SGM 2015; 162:191-205. [PMID: 26643057 DOI: 10.1099/mic.0.000220] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Iron acquisition is vital to microbial survival and is implicated in the virulence of many of the pathogens that reside in the cystic fibrosis (CF) lung. The multifaceted nature of iron acquisition by both bacterial and fungal pathogens encompasses a range of conserved and species-specific mechanisms, including secretion of iron-binding siderophores, utilization of siderophores from other species, release of iron from host iron-binding proteins and haemoproteins, and ferrous iron uptake. Pathogens adapt and deploy specific systems depending on iron availability, bioavailability of the iron pool, stage of infection and presence of competing pathogens. Understanding the dynamics of pathogen iron acquisition has the potential to unveil new avenues for therapeutic intervention to treat both acute and chronic CF infections. Here, we examine the range of strategies utilized by the primary CF pathogens to acquire iron and discuss the different approaches to targeting iron acquisition systems as an antimicrobial strategy.
Collapse
Affiliation(s)
- Jean Tyrrell
- Centre of Microbial Host Interactions, Institute of Technology Tallaght, Dublin D24KT9, Ireland
| | - Máire Callaghan
- Centre of Microbial Host Interactions, Institute of Technology Tallaght, Dublin D24KT9, Ireland
| |
Collapse
|
23
|
Li K, Bruner SD. Structure and functional analysis of the siderophore periplasmic binding protein from the fuscachelin gene cluster of T
hermobifida fusca. Proteins 2015; 84:118-28. [DOI: 10.1002/prot.24959] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Revised: 10/19/2015] [Accepted: 10/23/2015] [Indexed: 11/10/2022]
Affiliation(s)
- Kunhua Li
- Department of Chemistry; University of Florida; Gainesville Florida 32611
| | - Steven D. Bruner
- Department of Chemistry; University of Florida; Gainesville Florida 32611
| |
Collapse
|
24
|
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.
Collapse
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
| |
Collapse
|
25
|
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.
Collapse
|
26
|
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
|
27
|
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.
Collapse
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
| |
Collapse
|
28
|
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.
Collapse
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
| |
Collapse
|
29
|
Insights on how the Mycobacterium tuberculosis heme uptake pathway can be used as a drug target. Future Med Chem 2014; 5:1391-403. [PMID: 23919550 DOI: 10.4155/fmc.13.109] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Mycobacterium tuberculosis (Mtb) acquires non-heme iron through salicylate-derived siderophores termed mycobactins whereas heme iron is obtained through a cascade of heme uptake proteins. Three proteins are proposed to mediate Mtb heme iron uptake, a secreted heme transporter (Rv0203), and MmpL3 and MmpL11, which are potential transmembrane heme transfer proteins. Furthermore, MhuD, a cytoplasmic heme-degrading enzyme, has been identified. Rv0203, MmpL3 and MmpL11 are mycobacteria-specific proteins, making them excellent drug targets. Importantly, MmpL3, a necessary protein, has also been implicated in trehalose monomycolate export. Recent drug-discovery efforts revealed that MmpL3 is the target of several compounds with antimycobacterial activity. Inhibition of the Mtb heme uptake pathway has yet to be explored. We propose that inhibitor design could focus on heme analogs, with the goal of blocking specific steps of this pathway. In addition, heme uptake could be hijacked as a method of importing drugs into the mycobacterial cytosol.
Collapse
|
30
|
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.
Collapse
Affiliation(s)
- Gleb Pishchany
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | | | | | | | | | | | | | | |
Collapse
|
31
|
Abstract
Iron is an essential nutrient for both humans and pathogenic microbes. Because of its ability to exist in one of two oxidation states, iron is an ideal redox catalyst for diverse cellular processes including respiration and DNA replication. However, the redox potential of iron also contributes to its toxicity; thus, iron concentration and distribution must be carefully controlled. Given the absolute requirement for iron by virtually all human pathogens, an important facet of the innate immune system is to limit iron availability to invading microbes in a process termed nutritional immunity. Successful human pathogens must therefore possess mechanisms to circumvent nutritional immunity in order to cause disease. In this review, we discuss regulation of iron metabolism in the setting of infection and delineate strategies used by human pathogens to overcome iron-withholding defenses.
Collapse
Affiliation(s)
- James E Cassat
- Department of Pediatrics, Division of Pediatric Infectious Diseases, Vanderbilt University Medical Center, Nashville, TN 37237, USA
| | - Eric P Skaar
- Department of Pathology, Microbiology, & Immunology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
| |
Collapse
|
32
|
Ran Y, Malmirchegini GR, Clubb RT, Lei B. Axial ligand replacement mechanism in heme transfer from streptococcal heme-binding protein Shp to HtsA of the HtsABC transporter. Biochemistry 2013; 52:6537-47. [PMID: 23980583 PMCID: PMC3815476 DOI: 10.1021/bi400965u] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The heme-binding protein Shp of Group A Streptococcus rapidly transfers its heme to HtsA, the lipoprotein component of the HtsABC transporter, in a concerted two-step process with one kinetic phase. Heme axial residue-to-alanine replacement mutant proteins of Shp and HtsA (Shp(M66A), Shp(M153A), HtsA(M79A), and HtsA(H229A)) were used to probe the axial displacement mechanism of this heme transfer reaction. Ferric Shp(M66A) at high pH and Shp(M153A) have a pentacoordinate heme iron complex with a methionine axial ligand. ApoHtsA(M79A) efficiently acquires heme from ferric Shp but alters the reaction mechanism to two kinetic phases from a single phase in the wild-type protein reactions. In contrast, apoHtsA(H229A) cannot assimilate heme from ferric Shp. The conversion of pentacoordinate holoShp(M66A) into pentacoordinate holoHtsA(H229A) involves an intermediate, whereas holoHtsA(H229A) is directly formed from pentacoordinate holoShp(M153A). Conversely, apoHtsA(M79A) reacts with holoShp(M66A) and holoShp(M153A) in mechanisms with one and two kinetic phases, respectively. These results imply that the Met79 and His229 residues of HtsA displace the Met66 and Met153 residues of Shp, respectively. Structural docking analysis supports this mechanism of the specific axial residue displacement. Furthermore, the rates of the cleavage of the axial bond in Shp in the presence of a replacing HtsA axial residue are greater than that in the absence of a replacing HtsA axial residue. These findings reveal a novel heme transfer mechanism of the specific displacement of the Shp axial residues with the HtsA axial residues and the involvement of the HtsA axial residues in the displacement.
Collapse
Affiliation(s)
- Yanchao Ran
- Department of Immunology and Infectious Diseases, Montana State University, Bozeman, MT 59718
| | - G. Reza Malmirchegini
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095
| | - Robert T. Clubb
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095
| | - Benfang Lei
- Department of Immunology and Infectious Diseases, Montana State University, Bozeman, MT 59718
| |
Collapse
|
33
|
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.
Collapse
Affiliation(s)
- Mahamoudou Ouattara
- Department of Biology, College of Arts and Sciences, Georgia State University, Atlanta, GA 30303, USA
| | | | | | | | | | | |
Collapse
|
34
|
Loutet SA, Kobylarz MJ, Chau CHT, Murphy MEP. IruO is a reductase for heme degradation by IsdI and IsdG proteins in Staphylococcus aureus. J Biol Chem 2013; 288:25749-25759. [PMID: 23893407 DOI: 10.1074/jbc.m113.470518] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Staphylococcus aureus is a common hospital- and community-acquired bacterium that can cause devastating infections and is often multidrug-resistant. Iron acquisition is required by S. aureus during an infection, and iron acquisition pathways are potential targets for therapies. The gene NWMN2274 in S. aureus strain Newman is annotated as an oxidoreductase of the diverse pyridine nucleotide-disulfide oxidoreductase (PNDO) family. We show that NWMN2274 is an electron donor to IsdG and IsdI catalyzing the degradation of heme, and we have renamed this protein IruO. Recombinant IruO is a FAD-containing NADPH-dependent reductase. In the presence of NADPH and IruO, either IsdI or IsdG degraded bound heme 10-fold more rapidly than with the chemical reductant ascorbic acid. Varying IsdI-heme substrate and monitoring loss of the heme Soret band gave a K(m) of 15 ± 4 μM, a k(cat) of 5.2 ± 0.7 min(-1), and a k(cat)/K(m) of 5.8 × 10(3) M(-1) s(-1). From HPLC and electronic spectra, the major heme degradation products are 5-oxo-δ-bilirubin and 15-oxo-β-bilirubin (staphylobilins), as observed with ascorbic acid. Although heme degradation by IsdI or IsdG can occur in the presence of H2O2, the addition of catalase and superoxide dismutase did not disrupt NADPH/IruO heme degradation reactions. The degree of electron coupling between IruO and IsdI or IsdG remains to be determined. Homologs of IruO were identified by sequence similarity in the genomes of Gram-positive bacteria that possess IsdG-family heme oxygenases. A phylogeny of these homologs identifies a distinct clade of pyridine nucleotide-disulfide oxidoreductases likely involved in iron uptake systems. IruO is the likely in vivo reductant required for heme degradation by S. aureus.
Collapse
Affiliation(s)
- Slade A Loutet
- From the Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Marek J Kobylarz
- From the Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Crystal H T Chau
- From the Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Michael E P Murphy
- From the Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
| |
Collapse
|
35
|
Owens CP, Chim N, Graves AB, Harmston CA, Iniguez A, Contreras H, Liptak MD, Goulding CW. The Mycobacterium tuberculosis secreted protein Rv0203 transfers heme to membrane proteins MmpL3 and MmpL11. J Biol Chem 2013; 288:21714-28. [PMID: 23760277 DOI: 10.1074/jbc.m113.453076] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Mycobacterium tuberculosis is the causative agent of tuberculosis, which is becoming an increasingly global public health problem due to the rise of drug-resistant strains. While residing in the human host, M. tuberculosis needs to acquire iron for its survival. M. tuberculosis has two iron uptake mechanisms, one that utilizes non-heme iron and another that taps into the vast host heme-iron pool. To date, proteins known to be involved in mycobacterial heme uptake are Rv0203, MmpL3, and MmpL11. Whereas Rv0203 transports heme across the bacterial periplasm or scavenges heme from host heme proteins, MmpL3 and MmpL11 are thought to transport heme across the membrane. In this work, we characterize the heme-binding properties of the predicted extracellular soluble E1 domains of both MmpL3 and MmpL11 utilizing absorption, electron paramagnetic resonance, and magnetic circular dichroism spectroscopic methods. Furthermore, we demonstrate that Rv0203 transfers heme to both MmpL3-E1 and MmpL11-E1 domains at a rate faster than passive heme dissociation from Rv0203. This work elucidates a key step in the mycobacterial uptake of heme, and it may be useful in the development of anti-tuberculosis drugs targeting this pathway.
Collapse
Affiliation(s)
- Cedric P Owens
- Department of Molecular Biology and Biochemistry, University of California at Irvine, Irvine, California 92697, USA
| | | | | | | | | | | | | | | |
Collapse
|
36
|
Spirig T, Malmirchegini GR, Zhang J, Robson SA, Sjodt M, Liu M, Krishna Kumar K, Dickson CF, Gell DA, Lei B, Loo JA, Clubb RT. Staphylococcus aureus uses a novel multidomain receptor to break apart human hemoglobin and steal its heme. J Biol Chem 2012; 288:1065-78. [PMID: 23132864 DOI: 10.1074/jbc.m112.419119] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Staphylococcus aureus is a leading cause of life-threatening infections in the United States. It requires iron to grow, which must be actively procured from its host to successfully mount an infection. Heme-iron within hemoglobin (Hb) is the most abundant source of iron in the human body and is captured by S. aureus using two closely related receptors, IsdH and IsdB. Here we demonstrate that each receptor captures heme using two conserved near iron transporter (NEAT) domains that function synergistically. NMR studies of the 39-kDa conserved unit from IsdH (IsdH(N2N3), Ala(326)-Asp(660)) reveals that it adopts an elongated dumbbell-shaped structure in which its NEAT domains are properly positioned by a helical linker domain, whose three-dimensional structure is determined here in detail. Electrospray ionization mass spectrometry and heme transfer measurements indicate that IsdH(N2N3) extracts heme from Hb via an ordered process in which the receptor promotes heme release by inducing steric strain that dissociates the Hb tetramer. Other clinically significant Gram-positive pathogens capture Hb using receptors that contain multiple NEAT domains, suggesting that they use a conserved mechanism.
Collapse
Affiliation(s)
- Thomas Spirig
- Department of Chemistry and Biochemistry and the UCLA-Department of Energy Institute for Genomics and Proteomics, UCLA, Los Angeles, California 90095, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
37
|
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
| |
Collapse
|
38
|
Lewis VG, Ween MP, McDevitt CA. The role of ATP-binding cassette transporters in bacterial pathogenicity. PROTOPLASMA 2012; 249:919-942. [PMID: 22246051 DOI: 10.1007/s00709-011-0360-8] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 11/29/2011] [Indexed: 05/31/2023]
Abstract
The ATP-binding cassette transporter superfamily is present in all three domains of life. This ubiquitous class of integral membrane proteins have diverse biological functions, but their fundamental role involves the unidirectional translocation of compounds across cellular membranes in an ATP coupled process. The importance of this class of proteins in eukaryotic systems is well established as typified by their association with genetic diseases and roles in the multi-drug resistance of cancer. In stark contrast, the ABC transporters of prokaryotes have not been exhaustively investigated due to the sheer number of different roles and organisms in which they function. In this review, we examine the breadth of functions associated with microbial ABC transporters in the context of their contribution to bacterial pathogenicity and virulence.
Collapse
Affiliation(s)
- Victoria G Lewis
- Research Centre for Infectious Diseases, School of Molecular and Biomedical Science, University of Adelaide, Adelaide, South Australia, 5005, Australia
| | | | | |
Collapse
|
39
|
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.
Collapse
Affiliation(s)
- Michael T Tiedemann
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada
| | | | | |
Collapse
|
40
|
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.
Collapse
Affiliation(s)
- Cécile Wandersman
- Unité des Membranes Bactériennes, Institut Pasteur, Département de Microbiologie, 25-28, rue du Dr. Roux, 75724 Paris Cedex 15, France.
| | | |
Collapse
|
41
|
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]
|
42
|
Sheldon JR, Heinrichs DE. The iron-regulated staphylococcal lipoproteins. Front Cell Infect Microbiol 2012; 2:41. [PMID: 22919632 PMCID: PMC3417571 DOI: 10.3389/fcimb.2012.00041] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Accepted: 03/13/2012] [Indexed: 01/01/2023] Open
Abstract
Lipoproteins fulfill diverse roles in antibiotic resistance, adhesion, protein secretion, signaling and sensing, and many also serve as the substrate binding protein (SBP) partner to ABC transporters for the acquisition of a diverse array of nutrients including peptides, sugars, and scarcely abundant metals. In the staphylococci, the iron-regulated SBPs are significantly upregulated during iron starvation and function to sequester and deliver iron into the bacterial cell, enabling staphylococci to circumvent iron restriction imposed by the host environment. Accordingly, this subset of lipoproteins has been implicated in staphylococcal pathogenesis and virulence. Lipoproteins also activate the host innate immune response, triggered through Toll-like receptor-2 (TLR2) and, notably, the iron-regulated subset of lipoproteins are particularly immunogenic. In this review, we discuss the iron-regulated staphylococcal lipoproteins with regard to their biogenesis, substrate specificity, and impact on the host innate immune response.
Collapse
Affiliation(s)
- Jessica R Sheldon
- Department of Microbiology and Immunology, Western University, London ON, Canada
| | | |
Collapse
|
43
|
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.
Collapse
Affiliation(s)
- Ryota Abe
- Department of Medical Genome Sciences, School of Frontier Sciences, University of Tokyo, Minato-ku, Tokyo 108-8639, Japan
| | | | | | | | | |
Collapse
|
44
|
Wright JA, Nair SP. The lipoprotein components of the Isd and Hts transport systems are dispensable for acquisition of heme by Staphylococcus aureus. FEMS Microbiol Lett 2012; 329:177-85. [PMID: 22309509 DOI: 10.1111/j.1574-6968.2012.02519.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 01/31/2012] [Accepted: 02/01/2012] [Indexed: 12/01/2022] Open
Abstract
Heme is a key molecule for Staphylococcus aureus and is involved in many aspects of oxidative metabolism. Crucially, heme is required for the activity of cytochromes of the electron transport chain. Staphylococcus aureus is able to obtain heme either through biosynthesis or through acquisition from the host. Clinically persistent 'small colony variant' (SCV) forms of S. aureus are frequently deficient for heme biosynthesis, and disruption of the hemB gene produces stable heme-auxotrophic strains that reproduce many SCV phenotypes. We sought to address the role of heme transport in SCVs by deleting components of the two described heme import systems, the iron-regulated surface determinant (Isd) and heme transport system (Hts) in wild-type S. aureus and hemB mutant backgrounds. Analysis of the growth of S. aureus hemB strains either singly or doubly deficient in isdE and htsA in the presence and absence of heme or hemoglobin revealed that S. aureus is able to obtain exogenous heme in the absence of these transporter components. These data suggest the presence of additional, as yet unidentified transporter components that enable S. aureus to internalize exogenous heme and contradict the proposed model that IsdE can transfer heme to the HtsBC permease.
Collapse
Affiliation(s)
- John A Wright
- Department of Microbial Diseases, UCL Eastman Dental Institute, University College London, London, UK
| | | |
Collapse
|
45
|
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.
Collapse
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
| |
Collapse
|
46
|
Grigg JC, Mao CX, Murphy ME. Iron-Coordinating Tyrosine Is a Key Determinant of NEAT Domain Heme Transfer. J Mol Biol 2011; 413:684-98. [DOI: 10.1016/j.jmb.2011.08.047] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 08/13/2011] [Accepted: 08/23/2011] [Indexed: 11/29/2022]
|
47
|
Honsa ES, Fabian M, Cardenas AM, Olson JS, Maresso AW. The five near-iron transporter (NEAT) domain anthrax hemophore, IsdX2, scavenges heme from hemoglobin and transfers heme to the surface protein IsdC. J Biol Chem 2011; 286:33652-60. [PMID: 21808055 PMCID: PMC3190864 DOI: 10.1074/jbc.m111.241687] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2011] [Revised: 07/19/2011] [Indexed: 11/06/2022] Open
Abstract
Pathogenic bacteria require iron to replicate inside mammalian hosts. Recent studies indicate that heme acquisition in Gram-positive bacteria is mediated by proteins containing one or more near-iron transporter (NEAT) domains. Bacillus anthracis is a spore-forming, Gram-positive pathogen and the causative agent of anthrax disease. The rapid, extensive, and efficient replication of B. anthracis in host tissues makes this pathogen an excellent model organism for the study of bacterial heme acquisition. B. anthracis secretes two NEAT hemophores, IsdX1 and IsdX2. IsdX1 contains a single NEAT domain, whereas IsdX2 has five, a novel property among hemophores. To understand the functional significance of harboring multiple, non-identical NEAT domains, we purified each individual NEAT domain of IsdX2 as a GST fusion and analyzed the specific function of each domain as it relates to heme acquisition and transport. NEAT domains 1, 3, 4, and 5 all bind heme, with domain 5 having the highest affinity. All NEATs associate with hemoglobin, but only NEAT1 and -5 can extract heme from hemoglobin, seemingly by a specific and active process. NEAT1, -3, and -4 transfer heme to IsdC, a cell wall-anchored anthrax NEAT protein. These results indicate that IsdX2 has all the features required to acquire heme from the host and transport heme to the bacterial cell wall. Additionally, these results suggest that IsdX2 may accelerate iron import rates by acting as a "heme sponge" that enhances B. anthracis replication in iron-starved environments.
Collapse
Affiliation(s)
- Erin Sarah Honsa
- From the Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas 77030 and
| | - Marian Fabian
- the Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77096
| | - Ana Maria Cardenas
- From the Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas 77030 and
| | - John S. Olson
- the Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77096
| | - Anthony William Maresso
- From the Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas 77030 and
| |
Collapse
|
48
|
Nobles CL, Maresso AW. The theft of host heme by Gram-positive pathogenic bacteria. Metallomics 2011; 3:788-96. [PMID: 21725569 DOI: 10.1039/c1mt00047k] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The element iron is essential for bacteria and plays a key role in the virulence and pathology of bacterial diseases. The largest reservoir of iron within the human body is in protoporphyrin IX, the compound commonly referred to as heme and bound by hemoglobin. For many years, the study of heme uptake in bacteria was restricted to Gram-negative organisms. However, recent studies have shed light on how bacteria containing a thick peptidoglycan, such as Gram-positive bacteria, acquire and transport heme. This review summarizes old and new research covering the acquisition, transport, and utilization of heme in Gram-positive bacterial pathogens.
Collapse
Affiliation(s)
- Christopher L Nobles
- Molecular Virology and Microbiology, Baylor College of Medicine, One Baylor Plaza - BCM280, Houston, TX 77030, USA
| | | |
Collapse
|
49
|
Chu BCH, Vogel HJ. A structural and functional analysis of type III periplasmic and substrate binding proteins: their role in bacterial siderophore and heme transport. Biol Chem 2011; 392:39-52. [PMID: 21194366 DOI: 10.1515/bc.2011.012] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In Escherichia coli the Fhu, Fep and Fec transport systems are involved in the uptake of chelated ferric iron-siderophore complexes, whereas in pathogenic strains heme can also be used as an iron source. An essential step in these pathways is the movement of the ferric-siderophore complex or heme from the outer membrane transporter across the periplasm to the cognate cytoplasmic membrane ATP-dependent transporter. This is accomplished in each case by a dedicated periplasmic binding protein (PBP). Ferric-siderophore binding PBPs belong to the PBP protein superfamily and adopt a bilobal type III structural fold in which the two independently folded amino and carboxy terminal domains are linked together by a single long α-helix of approximately 20 amino acids. Recent structural studies reveal how the PBPs of the Fhu, Fep, Fec and Chu systems are able to bind their corresponding ligands. These complex structures will be discussed and placed in the context of our current understanding of the entire type III family of Gram-negative periplasmic binding proteins and related Gram-positive substrate binding proteins.
Collapse
Affiliation(s)
- Byron C H Chu
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | | |
Collapse
|
50
|
Gaudin CFM, Grigg JC, Arrieta AL, Murphy MEP. Unique heme-iron coordination by the hemoglobin receptor IsdB of Staphylococcus aureus. Biochemistry 2011; 50:5443-52. [PMID: 21574663 PMCID: PMC3114464 DOI: 10.1021/bi200369p] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
![]()
Iron is an essential requirement for life for nearly all organisms. The human pathogen Staphylococcus aureus is able to acquire iron from the heme cofactor of hemoglobin (Hb) released from lysed erythrocytes. IsdB, the predominant Hb receptor of S. aureus, is a cell wall-anchored protein that is composed of two NEAT domains. The N-terminal NEAT domain (IsdB-N1) binds Hb, and the C-terminal NEAT domain (IsdB-N2) relays heme to IsdA for transport into the cell. Here we present the 1.45 Å resolution X-ray crystal structure of the IsdB-N2–heme complex. While the structure largely conforms to the eight-strand β-sandwich fold seen in other NEAT domains such as IsdA-N and uses a conserved Tyr residue to coordinate heme-iron, a Met residue is also involved in iron coordination, resulting in a novel Tyr-Met hexacoordinate heme-iron state. The kinetics of the transfer of heme from IsdB-N2 to IsdA-N can be modeled as a two-step process. The rate of transfer of heme between the isolated NEAT domains (82 s–1) was found to be similar to that measured for the full-length proteins. Replacing the iron coordinating Met with Leu did not abrogate high-affinity heme binding but did reduce the heme transfer rate constant by more than half. This unusual Met-Tyr heme coordination may also bestow properties on IsdB that help it to bind heme in different oxidation states or extract heme from hemoglobin.
Collapse
Affiliation(s)
- Catherine F M Gaudin
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, Vancouver, BC, Canada V6T 1Z3
| | | | | | | |
Collapse
|