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Li Y, Han S, Gao H. Heme homeostasis and its regulation by hemoproteins in bacteria. MLIFE 2024; 3:327-342. [PMID: 39359680 PMCID: PMC11442138 DOI: 10.1002/mlf2.12120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 02/08/2024] [Accepted: 02/23/2024] [Indexed: 10/04/2024]
Abstract
Heme is an important cofactor and a regulatory molecule involved in various physiological processes in virtually all living cellular organisms, and it can also serve as the primary iron source for many bacteria, particularly pathogens. However, excess heme is cytotoxic to cells. In order to meet physiological needs while preventing deleterious effects, bacteria have evolved sophisticated cellular mechanisms to maintain heme homeostasis. Recent advances in technologies have shaped our understanding of the molecular mechanisms that govern the biological processes crucial to heme homeostasis, including synthesis, acquisition, utilization, degradation, trafficking, and efflux, as well as their regulation. Central to these mechanisms is the regulation of the heme, by the heme, and for the heme. In this review, we present state-of-the-art findings covering the biochemical, physiological, and structural characterization of important, newly identified hemoproteins/systems involved in heme homeostasis.
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Affiliation(s)
- Yingxi Li
- Institute of Microbiology and College of Life SciencesZhejiang UniversityHangzhouChina
| | - Sirui Han
- Institute of Microbiology and College of Life SciencesZhejiang UniversityHangzhouChina
| | - Haichun Gao
- Institute of Microbiology and College of Life SciencesZhejiang UniversityHangzhouChina
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2
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Knejski PP, Erramilli SK, Kossiakoff AA. Chaperone-assisted cryo-EM structure of P. aeruginosa PhuR reveals molecular basis for heme binding. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.08.01.551527. [PMID: 37577460 PMCID: PMC10418163 DOI: 10.1101/2023.08.01.551527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
Pathogenic bacteria, such as Pseudomonas aeruginosa, depend on scavenging heme for the acquisition of iron, an essential nutrient. The TonB-dependent transporter (TBDT) PhuR is the major heme uptake protein in P. aeruginosa clinical isolates. However, a comprehensive understanding of heme recognition and TBDT transport mechanisms, especially PhuR, remains limited. In this study, we employed single-particle cryogenic electron microscopy (cryo-EM) and a phage display-generated synthetic antibody (sAB) as a fiducial marker to enable the determination of a high-resolution (2.5 Å) structure of PhuR with a bound heme. Notably, the structure reveals iron coordination by Y529 on a conserved extracellular loop, shedding light on the role of tyrosine in heme binding. Biochemical assays and negative-stain EM demonstrated that the sAB specifically targets the heme-bound state of PhuR. These findings provide insights into PhuR's heme binding and offer a template for developing conformation-specific sABs against outer membrane proteins (OMPs) for structure-function investigations.
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Affiliation(s)
- Paweł P. Knejski
- Deparment of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
- Laboratory of Medical Biology, Faculty of Biotechnology, University of Wrocław, Wrocław 50-383, Poland
- Present address: Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zürich, Zürich 8093, Switzerland
| | - Satchal K. Erramilli
- Deparment of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
- Present address: Meso Scale Diagnostics, LLC, Rockville, Maryland 20850, USA
| | - Anthony A. Kossiakoff
- Deparment of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
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3
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Knejski PP, Erramilli SK, Kossiakoff AA. Chaperone-assisted cryo-EM structure of P. aeruginosa PhuR reveals molecular basis for heme binding. Structure 2024; 32:411-423.e6. [PMID: 38325368 PMCID: PMC10997469 DOI: 10.1016/j.str.2024.01.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 12/14/2023] [Accepted: 01/11/2024] [Indexed: 02/09/2024]
Abstract
Pathogenic bacteria, such as Pseudomonas aeruginosa, depend on scavenging heme for the acquisition of iron, an essential nutrient. The TonB-dependent transporter (TBDT) PhuR is the major heme uptake protein in P. aeruginosa clinical isolates. However, a comprehensive understanding of heme recognition and TBDT transport mechanisms, especially PhuR, remains limited. In this study, we employed single-particle cryogenic electron microscopy (cryo-EM) and a phage display-generated synthetic antibody (sAB) as a fiducial marker to enable the determination of a high-resolution (2.5 Å) structure of PhuR with a bound heme. Notably, the structure reveals iron coordination by Y529 on a conserved extracellular loop, shedding light on the role of tyrosine in heme binding. Biochemical assays and negative-stain EM demonstrated that the sAB specifically targets the heme-bound state of PhuR. These findings provide insights into PhuR's heme binding and offer a template for developing conformation-specific sABs against outer membrane proteins (OMPs) for structure-function investigations.
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Affiliation(s)
- Paweł P Knejski
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA; Laboratory of Medical Biology, Faculty of Biotechnology, University of Wrocław, 50-383 Wrocław, Poland
| | - Satchal K Erramilli
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA.
| | - Anthony A Kossiakoff
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA; Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA.
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4
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Gouda AM, Soltan MA, Abd-Elghany K, Sileem AE, Elnahas HM, Ateya MAM, Elbatreek MH, Darwish KM, Bogari HA, Lashkar MO, Aldurdunji MM, Elhady SS, Ahmad TA, Said AM. Integration of immunoinformatics and cheminformatics to design and evaluate a multitope vaccine against Klebsiella pneumoniae and Pseudomonas aeruginosa coinfection. Front Mol Biosci 2023; 10:1123411. [PMID: 36911530 PMCID: PMC9999731 DOI: 10.3389/fmolb.2023.1123411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Accepted: 01/26/2023] [Indexed: 02/16/2023] Open
Abstract
Introduction: Klebsiella pneumoniae (K. pneumoniae) and Pseudomonas aeruginosa (P. aeruginosa) are the most common Gram-negative bacteria associated with pneumonia and coinfecting the same patient. Despite their high virulence, there is no effective vaccine against them. Methods: In the current study, the screening of several proteins from both pathogens highlighted FepA and OmpK35 for K. pneumonia in addition to HasR and OprF from P. aeruginosa as promising candidates for epitope mapping. Those four proteins were linked to form a multitope vaccine, that was formulated with a suitable adjuvant, and PADRE peptides to finalize the multitope vaccine construct. The final vaccine's physicochemical features, antigenicity, toxicity, allergenicity, and solubility were evaluated for use in humans. Results: The output of the computational analysis revealed that the designed multitope construct has passed these assessments with satisfactory scores where, as the last stage, we performed a molecular docking study between the potential vaccine construct and K. pneumonia associated immune receptors, TLR4 and TLR2, showing affinitive to both targets with preferentiality for the TLR4 receptor protein. Validation of the docking studies has proceeded through molecular dynamics simulation, which estimated a strong binding and supported the nomination of the designed vaccine as a putative solution for K. pneumoniae and P. aeruginosa coinfection. Here, we describe the approach for the design and assessment of our potential vaccine.
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Affiliation(s)
- Ahmed M Gouda
- Department of Pharmacy Practice, Faculty of Pharmacy, Zagazig University, Zagazig, Egypt
| | - Mohamed A Soltan
- Department of Microbiology and Immunology, Faculty of Pharmacy, Sinai University-Kantara Branch, Ismailia, Egypt
| | - Khalid Abd-Elghany
- Department of Microbiology-Microbial Biotechnology, Egyptian Drug Authority, Giza, Egypt
| | - Ashraf E Sileem
- Department of Chest Diseases, Faculty of Medicine, Zagazig University, Zagazig, Egypt
| | - Hanan M Elnahas
- Department of Pharmaceutical and Industrial Pharmacy, Faculty of Pharmacy, Zagazig University, Zagazig, Egypt
| | | | - Mahmoud H Elbatreek
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Zagazig University, Zagazig, Egypt
| | - Khaled M Darwish
- Department of Medicinal Chemistry, Faculty of Pharmacy, Suez Canal University, Ismailia, Egypt
| | - Hanin A Bogari
- Department of Pharmacy Practice, Faculty of Pharmacy, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Manar O Lashkar
- Department of Pharmacy Practice, Faculty of Pharmacy, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Mohammed M Aldurdunji
- Department of Clinical Pharmacy, College of Pharmacy, Umm Al-Qura University, Makkah, Saudi Arabia
| | - Sameh S Elhady
- Department of Natural Products, Faculty of Pharmacy, King Abdulaziz University, Jeddah, Saudi Arabia.,Center for Artificial Intelligence in Precision Medicines, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Tarek A Ahmad
- Library Sector, Bibliotheca Alexandrina, Alexandria, Egypt
| | - Ahmed Mohamed Said
- Department of Chest Diseases, Faculty of Medicine, Zagazig University, Zagazig, Egypt
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5
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Donegan RK. The role of host heme in bacterial infection. Biol Chem 2022; 403:1017-1029. [PMID: 36228088 DOI: 10.1515/hsz-2022-0192] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Accepted: 09/14/2022] [Indexed: 11/15/2022]
Abstract
Heme is an indispensable cofactor for almost all aerobic life, including the human host and many bacterial pathogens. During infection, heme and hemoproteins are the largest source of bioavailable iron, and pathogens have evolved various heme acquisition pathways to satisfy their need for iron and heme. Many of these pathways are regulated transcriptionally by intracellular iron levels, however, host heme availability and intracellular heme levels have also been found to regulate heme uptake in some species. Knowledge of these pathways has helped to uncover not only how these bacteria incorporate host heme into their metabolism but also provided insight into the importance of host heme as a nutrient source during infection. Within this review is covered multiple aspects of the role of heme at the host pathogen interface, including the various routes of heme biosynthesis, how heme is sequestered by the host, and how heme is scavenged by bacterial pathogens. Also discussed is how heme and hemoproteins alter the behavior of the host immune system and bacterial pathogens. Finally, some unanswered questions about the regulation of heme uptake and how host heme is integrated into bacterial metabolism are highlighted.
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Affiliation(s)
- Rebecca K Donegan
- Department of Chemistry, Barnard College, 3009 Broadway, New York, NY, 10027, USA
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6
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Krüger A, Keppel M, Sharma V, Frunzke J. The diversity of heme sensor systems - heme-responsive transcriptional regulation mediated by transient heme protein interactions. FEMS Microbiol Rev 2022; 46:6506450. [PMID: 35026033 DOI: 10.1093/femsre/fuac002] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 12/21/2021] [Accepted: 01/11/2022] [Indexed: 11/13/2022] Open
Abstract
Heme is a versatile molecule that is vital for nearly all cellular life by serving as prosthetic group for various enzymes or as nutritional iron source for diverse microbial species. However, elevated levels of heme molecule are toxic to cells. The complexity of this stimulus has shaped the evolution of diverse heme sensor systems, which are involved in heme-dependent transcriptional regulation in eukaryotes and prokaryotes. The functions of these systems are manifold - ranging from the specific control of heme detoxification or uptake systems to the global integration of heme and iron homeostasis. This review focuses on heme sensor systems, regulating heme homeostasis by transient heme protein interaction. We provide an overview of known heme-binding motifs in prokaryotic and eukaryotic transcription factors. Besides the central ligands, the surrounding amino acid environment was shown to play a pivotal role in heme binding. The diversity of heme-regulatory systems therefore illustrates that prediction based on pure sequence information is hardly possible and requires careful experimental validation. Comprehensive understanding of heme-regulated processes is not only important for our understanding of cellular physiology, but also provides a basis for the development of novel antibacterial drugs and metabolic engineering strategies.
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Affiliation(s)
- Aileen Krüger
- Forschungszentrum Jülich GmbH, Institute for Bio- and Geosciences 1, IBG1, 52425 Jülich, Germany
| | - Marc Keppel
- Forschungszentrum Jülich GmbH, Institute for Bio- and Geosciences 1, IBG1, 52425 Jülich, Germany
| | - Vikas Sharma
- Forschungszentrum Jülich GmbH, Institute for Bio- and Geosciences 1, IBG1, 52425 Jülich, Germany
| | - Julia Frunzke
- Forschungszentrum Jülich GmbH, Institute for Bio- and Geosciences 1, IBG1, 52425 Jülich, Germany
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7
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Robinson EA, Frankenberg-Dinkel N, Xue F, Wilks A. Recombinant Production of Biliverdin IXβ and δ Isomers in the T7 Promoter Compatible Escherichia coli Nissle. Front Microbiol 2021; 12:787609. [PMID: 34956154 PMCID: PMC8692735 DOI: 10.3389/fmicb.2021.787609] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 11/11/2021] [Indexed: 11/23/2022] Open
Abstract
The ability to obtain purified biliverdin IX (BVIX) isomers other than the commercially available BVIXα is limited due to the low yields obtained by the chemical coupled oxidation of heme. Chemical oxidation requires toxic chemicals, has very poor BVIX yields (<0.05%), and is not conducive to scalable production. Alternative approaches utilizing recombinant E. coli BL21 expressing a cyanobacterial heme oxygenase have been employed for the production BVIXα, but yields are limited by the rate of endogenous heme biosynthesis. Furthermore, the emerging roles of BVIXβ and BVIXδ in biology and their lack of commercial availability has led to a need for an efficient and scalable method with the flexibility to produce all three physiologically relevant BVIX isomers. Herein, we have taken advantage of an optimized non-pathogenic E. coli Nissle (EcN(T7)) strain that encodes an endogenous heme transporter and an integrated T7 polymerase gene. Protein production of the Pseudomonas aeruginosa BVIXβ and BVIXδ selective heme oxygenase (HemO) or its BVIXα producing mutant (HemOα) in the EcN(T7) strain provides a scalable method to obtain all three isomers, that is not limited by the rate of endogenous heme biosynthesis, due to the natural ability of EcN(T7) to transport extracellular heme. Additionally, we have optimized our previous LC-MS/MS protocol for semi-preparative separation and validation of the BVIX isomers. Utilizing this new methodology for scalable production and separation we have increased the yields of the BVIXβ and -δ isomers >300-fold when compared to the chemical oxidation of heme.
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Affiliation(s)
- Elizabeth A. Robinson
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD, United States
| | - Nicole Frankenberg-Dinkel
- Fachbereich Biologie, Abt. Mikrobiologie, Technische Universität Kaiserlautern, Kaiserslautern, Germany
| | - Fengtian Xue
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD, United States
| | - Angela Wilks
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD, United States
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8
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Extracellular haem utilization by the opportunistic pathogen Pseudomonas aeruginosa and its role in virulence and pathogenesis. Adv Microb Physiol 2021; 79:89-132. [PMID: 34836613 DOI: 10.1016/bs.ampbs.2021.07.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Iron is an essential micronutrient for all bacteria but presents a significant challenge given its limited bioavailability. Furthermore, iron's toxicity combined with the need to maintain iron levels within a narrow physiological range requires integrated systems to sense, regulate and transport a variety of iron complexes. Most bacteria encode systems to chelate and transport ferric iron (Fe3+) via siderophore receptor mediated uptake or via cytoplasmic energy dependent transport systems. Pathogenic bacteria have further lowered the barrier to iron acquisition by employing systems to utilize haem as a source of iron. Haem, a lipophilic and toxic molecule, presents a significant challenge for transport into the cell. As such pathogenic bacteria have evolved sophisticated cell surface signaling (CSS) and transport systems to sense and obtain haem from the host. Once internalized haem is cleaved by both oxidative and non-oxidative mechanisms to release iron. Herein we summarize our current understanding of the mechanism of haem sensing, uptake and utilization in Pseudomonas aeruginosa, its role in pathogenesis and virulence, and the potential of these systems as antimicrobial targets.
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9
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Stasiuk R, Krucoń T, Matlakowska R. Biosynthesis of Tetrapyrrole Cofactors by Bacterial Community Inhabiting Porphyrine-Containing Shale Rock (Fore-Sudetic Monocline). Molecules 2021; 26:6746. [PMID: 34771152 PMCID: PMC8587615 DOI: 10.3390/molecules26216746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Revised: 10/28/2021] [Accepted: 11/04/2021] [Indexed: 11/16/2022] Open
Abstract
This study describes for the first time the comprehensive characterization of tetrapyrrole cofactor biosynthetic pathways developed for bacterial community (BC) inhabiting shale rock. Based on the genomic and proteomic metadata, we have detailed the biosynthesis of siroheme, heme, cobalamin, and the major precursor uroporphyrinogen III by a deep BC living on a rock containing sedimentary tetrapyrrole compounds. The obtained results showed the presence of incomplete heme and cobalamin biosynthesis pathways in the studied BC. At the same time, the production of proteins containing these cofactors, such as cytochromes, catalases and sulfite reductase, was observed. The results obtained are crucial for understanding the ecology of bacteria inhabiting shale rock, as well as their metabolism and potential impact on the biogeochemistry of these rocks. Based on the findings, we hypothesize that the bacteria may use primary or modified sedimentary porphyrins and their degradation products as precursors for synthesizing tetrapyrrole cofactors. Experimental testing of this hypothesis is of course necessary, but its evidence would point to an important and unique phenomenon of the tetrapyrrole ring cycle on Earth involving bacteria.
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Affiliation(s)
- Robert Stasiuk
- Department of Geomicrobiology, Institute of Microbiology, Faculty of Biology, University of Warsaw, 02-096 Warsaw, Poland;
| | - Tomasz Krucoń
- Department of Environmental Microbiology and Biotechnology, Institute of Microbiology, Faculty of Biology, University of Warsaw, 02-096 Warsaw, Poland;
| | - Renata Matlakowska
- Department of Geomicrobiology, Institute of Microbiology, Faculty of Biology, University of Warsaw, 02-096 Warsaw, Poland;
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10
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Dent AT, Brimberry M, Albert T, Lanzilotta WN, Moënne-Loccoz P, Wilks A. Axial Heme Coordination by the Tyr-His Motif in the Extracellular Hemophore HasAp Is Critical for the Release of Heme to the HasR Receptor of Pseudomonas aeruginosa. Biochemistry 2021; 60:2549-2559. [PMID: 34324310 DOI: 10.1021/acs.biochem.1c00389] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Pseudomonas aeruginosa senses extracellular heme via an extra cytoplasmic function σ factor that is activated upon interaction of the hemophore holo-HasAp with the HasR receptor. Herein, we show Y75H holo-HasAp interacts with HasR but is unable to release heme for signaling and uptake. To understand this inhibition, we undertook a spectroscopic characterization of Y75H holo-HasAp by resonance Raman (RR), electron paramagnetic resonance (EPR), and X-ray crystallography. The RR spectra are consistent with a mixed six-coordinate high-spin (6cHS), six-coordinate low-spin (6cLS) heme configuration and an H218O exchangeable FeIII-O stretching frequency with 16O/18O and H/D isotope shifts that support a two-body Fe-OH2 oscillator with (iron-hydroxy)-like character as both hydrogen atoms are engaged in short hydrogen bond interactions with protein side chains. Further support comes from the EPR spectrum of Y75H holo-HasAp that shows a LS rhombic signal with ligand-field splitting values intermediate between those of His-hydroxy and bis-His ferric hemes. The crystal structure of Y75H holo-HasAp confirmed the coordinated solvent molecule hydrogen bonded through H75 and H83. The long-range conformational rearrangement of HasAp upon heme binding can still take place in Y75H holo-HasAp, because the intercalation of a hydroxy ligand between the heme iron and H75 allows the variant to reproduce the heme binding pocket observed in wild-type holo-HasAp. However, in the absence of a covalent linkage to the Y75 loop combined with the malleability provided by the bracketing H75 and H83 hydrogen bonds, either the hydroxy sixth ligand remains bound after complexation of Y75H holo-HasAp with HasR or rearrangement and coordination of H85 prevent heme transfer.
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Affiliation(s)
- Alecia T Dent
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, 20 Penn Street, Baltimore, Maryland 21201, United States
| | - Marley Brimberry
- Department of Biochemistry and Molecular Biology, Franklin College of Arts and Sciences, University of Georgia, Athens, Georgia 30602, United States
| | - Therese Albert
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, Portland, Oregon 97239, United States
| | - William N Lanzilotta
- Department of Biochemistry and Molecular Biology, Franklin College of Arts and Sciences, University of Georgia, Athens, Georgia 30602, United States
| | - Pierre Moënne-Loccoz
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, Portland, Oregon 97239, United States
| | - Angela Wilks
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, 20 Penn Street, Baltimore, Maryland 21201, United States
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11
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An Exposed Outer Membrane Hemin-Binding Protein Facilitates Hemin Transport by a TonB-Dependent Receptor in Riemerella anatipestifer. Appl Environ Microbiol 2021; 87:e0036721. [PMID: 33990314 DOI: 10.1128/aem.00367-21] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Iron is an essential element for the replication of most bacteria, including Riemerella anatipestifer, a Gram-negative bacterial pathogen of ducks and other birds. R. anatipestifer utilizes hemoglobin-derived hemin as an iron source; however, the mechanism by which this bacterium acquires hemin from hemoglobin is largely unknown. Here, rhuA disruption was shown to impair iron utilization from duck hemoglobin in R. anatipestifer CH-1. Moreover, the putative lipoprotein RhuA was identified as a surface-exposed, outer membrane hemin-binding protein, but it could not extract hemin from duck hemoglobin. Mutagenesis studies showed that recombinant RhuAY144A, RhuAY177A, and RhuAH149A lost hemin-binding ability, suggesting that amino acid sites at tyrosine 144 (Y144), Y177, and histidine 149 (H149) are crucial for hemin binding. Furthermore, rhuR, the gene adjacent to rhuA, encodes a TonB2-dependent hemin transporter. The function of rhuA in duck hemoglobin utilization was abolished in the rhuR mutant strain, and recombinant RhuA was able to bind the cell surface of R. anatipestifer CH-1 ΔrhuA rather than R. anatipestifer CH-1 ΔrhuR ΔrhuA, indicating that RhuA associates with RhuR to function. The sequence of the RhuR-RhuA hemin utilization locus exhibits no similarity to those of characterized hemin transport systems. Thus, this locus is a novel hemin uptake locus with homologues distributed mainly in the Bacteroidetes phylum. IMPORTANCE In vertebrates, hemin from hemoglobin is an important iron source for infectious bacteria. Many bacteria can obtain hemin from hemoglobin, but the mechanisms of hemin acquisition from hemoglobin differ among bacteria. Moreover, most studies have focused on the mechanism of hemin acquisition from mammalian hemoglobin. In this study, we found that the RhuR-RhuA locus of R. anatipestifer CH-1, a duck pathogen, is involved in hemin acquisition from duck hemoglobin via a unique pathway. RhuA was identified as an exposed outer membrane hemin-binding protein, and RhuR was identified as a TonB2-dependent hemin transporter. Moreover, the function of RhuA in hemoglobin utilization is RhuR dependent and not vice versa. The homologues of RhuR and RhuA are widely distributed in bacteria in marine environments, animals, and plants, representing a novel hemin transportation system of Gram-negative bacteria. This study not only was important for understanding hemin uptake in R. anatipestifer but also enriched the knowledge about the hemin transportation pathway in Gram-negative bacteria.
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12
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Robinson EA, Wilks A, Xue F. Repurposing Acitretin as an Antipseudomonal Agent Targeting the Pseudomonas aeruginosa Iron-Regulated Heme Oxygenase. Biochemistry 2021; 60:689-698. [PMID: 33621054 DOI: 10.1021/acs.biochem.0c00895] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Iron is an essential micronutrient for the survival and virulence of the bacterial pathogen Pseudomonas aeruginosa. To overcome iron withholding and successfully colonize a host, P. aeruginosa uses a variety of mechanisms to acquire iron, including the secretion of high-affinity iron chelators (siderophores) or the uptake and utilization of heme. P. aeruginosa heme oxygenase (HemO) plays pivotal roles in heme sensing, uptake, and utilization and has emerged as a therapeutic target for the development of antipseudomonal agents. Using a high-throughput fluorescence quenching assay combined with minimum inhibitory concentration measurements, we screened the Selleck Bioactive collection of 2100 compounds and identified acitretin, a Food and Drug Administration-approved oral retinoid, as a potent and selective inhibitor of HemO. Acitretin binds to HemO with a KD value of 0.10 ± 0.02 μM and inhibits the growth of P. aeruginosa PAO1 with an IC50 of 70 ± 18 μg/mL. In addition, acitretin showed good selectivity for HemO, which uniquely generates BVIXβ/δ, over human heme oxygenase (hHO1) and other BVIXα-producing homologues such as the heme oxygenases from Neisseria meningitidis (nmHO) and Acinetobacter baumannii (abHO). The binding of acitretin within the HemO active site was confirmed by 1H-15N heteronuclear single-quantum coherence nuclear magnetic resonance, and molecular modeling provided further insight into potential interactions of acitretin with residues specific for orienting heme in the β/δ selective HemO. Moreover, at 20 μM, acitretin inhibited the enzymatic activity of HemO in P. aeruginosa cells by >60% and effectively blocked the ability of P. aeruginosa to sense and acquire heme as demonstrated in the β-galactosidase transcriptional reporter assay.
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Affiliation(s)
- Elizabeth A Robinson
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, 20 Penn Street, Baltimore, Maryland 21201, United States
| | - Angela Wilks
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, 20 Penn Street, Baltimore, Maryland 21201, United States
| | - Fengtian Xue
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, 20 Penn Street, Baltimore, Maryland 21201, United States
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13
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Wilson T, Mouriño S, Wilks A. The heme-binding protein PhuS transcriptionally regulates the Pseudomonas aeruginosa tandem sRNA prrF1,F2 locus. J Biol Chem 2021; 296:100275. [PMID: 33428928 PMCID: PMC7948967 DOI: 10.1016/j.jbc.2021.100275] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 01/04/2021] [Accepted: 01/07/2021] [Indexed: 11/18/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen requiring iron for its survival and virulence. P. aeruginosa can acquire iron from heme via the nonredundant heme assimilation system and Pseudomonas heme uptake (Phu) systems. Heme transported by either the heme assimilation system or Phu system is sequestered by the cytoplasmic protein PhuS. Furthermore, PhuS has been shown to specifically transfer heme to the iron-regulated heme oxygenase HemO. As the PhuS homolog ShuS from Shigella dysenteriae was observed to bind DNA as a function of its heme status, we sought to further determine if PhuS, in addition to its role in regulating heme flux through HemO, functions as a DNA-binding protein. Herein, through a combination of chromatin immunoprecipitation–PCR, EMSA, and fluorescence anisotropy, we show that apo-PhuS but not holo-PhuS binds upstream of the tandem iron-responsive sRNAs prrF1,F2. Previous studies have shown the PrrF sRNAs are required for sparing iron for essential proteins during iron starvation. Furthermore, under certain conditions, a heme-dependent read through of the prrF1 terminator yields the longer PrrH transcript. Quantitative PCR analysis of P. aeruginosa WT and ΔphuS strains shows that loss of PhuS abrogates the heme-dependent regulation of PrrF and PrrH levels. Taken together, our data show that PhuS, in addition to its role in extracellular heme metabolism, also functions as a transcriptional regulator by modulating PrrF and PrrH levels in response to heme. This dual function of PhuS is central to integrating extracellular heme utilization into the PrrF/PrrH sRNA regulatory network that is critical for P. aeruginosa adaptation and virulence within the host.
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Affiliation(s)
- Tyree Wilson
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland, USA
| | - Susana Mouriño
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland, USA
| | - Angela Wilks
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland, USA.
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