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Klebba PE, Newton SMC, Six DA, Kumar A, Yang T, Nairn BL, Munger C, Chakravorty S. Iron Acquisition Systems of Gram-negative Bacterial Pathogens Define TonB-Dependent Pathways to Novel Antibiotics. Chem Rev 2021; 121:5193-5239. [PMID: 33724814 PMCID: PMC8687107 DOI: 10.1021/acs.chemrev.0c01005] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Iron is an indispensable metabolic cofactor in both pro- and eukaryotes, which engenders a natural competition for the metal between bacterial pathogens and their human or animal hosts. Bacteria secrete siderophores that extract Fe3+ from tissues, fluids, cells, and proteins; the ligand gated porins of the Gram-negative bacterial outer membrane actively acquire the resulting ferric siderophores, as well as other iron-containing molecules like heme. Conversely, eukaryotic hosts combat bacterial iron scavenging by sequestering Fe3+ in binding proteins and ferritin. The variety of iron uptake systems in Gram-negative bacterial pathogens illustrates a range of chemical and biochemical mechanisms that facilitate microbial pathogenesis. This document attempts to summarize and understand these processes, to guide discovery of immunological or chemical interventions that may thwart infectious disease.
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Affiliation(s)
- Phillip E Klebba
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506, United States
| | - Salete M C Newton
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506, United States
| | - David A Six
- Venatorx Pharmaceuticals, Inc., 30 Spring Mill Drive, Malvern, Pennsylvania 19355, United States
| | - Ashish Kumar
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506, United States
| | - Taihao Yang
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506, United States
| | - Brittany L Nairn
- Department of Biological Sciences, Bethel University, 3900 Bethel Drive, St. Paul, Minnesota 55112, United States
| | - Colton Munger
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506, United States
| | - Somnath Chakravorty
- Jacobs School of Medicine and Biomedical Sciences, SUNY Buffalo, Buffalo, New York 14203, United States
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Jaworska K, Ludwiczak M, Murawska E, Raczkowska A, Brzostek K. The Regulator OmpR in Yersinia enterocolitica Participates in Iron Homeostasis by Modulating Fur Level and Affecting the Expression of Genes Involved in Iron Uptake. Int J Mol Sci 2021; 22:ijms22031475. [PMID: 33540627 PMCID: PMC7867234 DOI: 10.3390/ijms22031475] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 01/29/2021] [Accepted: 01/29/2021] [Indexed: 12/02/2022] Open
Abstract
In this study, we found that the loss of OmpR, the response regulator of the two-component EnvZ/OmpR system, increases the cellular level of Fur, the master regulator of iron homeostasis in Y. enterocolitica. Furthermore, we demonstrated that transcription of the fur gene from the YePfur promoter is subject to negative OmpR-dependent regulation. Four putative OmpR-binding sites (OBSs) were indicated by in silico analysis of the fur promoter region, and their removal affected OmpR-dependent fur expression. Moreover, OmpR binds specifically to the predicted OBSs which exhibit a distinct hierarchy of binding affinity. Finally, the data demonstrate that OmpR, by direct binding to the promoters of the fecA, fepA and feoA genes, involved in the iron transport and being under Fur repressor activity, modulates their expression. It seems that the negative effect of OmpR on fecA and fepA transcription is sufficient to counteract the indirect, positive effect of OmpR resulting from decreasing the Fur repressor level. The expression of feoA was positively regulated by OmpR and this mode of action seems to be direct and indirect. Together, the expression of fecA, fepA and feoA in Y. enterocolitica has been proposed to be under a complex mode of regulation involving OmpR and Fur regulators.
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Smith AT, Linkous RO, Max NJ, Sestok AE, Szalai VA, Chacón KN. The FeoC [4Fe-4S] Cluster Is Redox-Active and Rapidly Oxygen-Sensitive. Biochemistry 2019; 58:4935-4949. [PMID: 31713418 DOI: 10.1021/acs.biochem.9b00745] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The acquisition of iron is essential to establishing virulence among most pathogens. Under acidic and/or anaerobic conditions, most bacteria utilize the widely distributed ferrous iron (Fe2+) uptake (Feo) system to import metabolically-required iron. The Feo system is inadequately understood at the atomic, molecular, and mechanistic levels, but we do know it is composed of a main membrane component (FeoB) essential for iron translocation, as well as two small, cytosolic proteins (FeoA and FeoC) hypothesized to function as accessories to this process. FeoC has many hypothetical functions, including that of an iron-responsive transcriptional regulator. Here, we demonstrate for the first time that Escherichia coli FeoC (EcFeoC) binds an [Fe-S] cluster. Using electronic absorption, X-ray absorption, and electron paramagnetic resonance spectroscopies, we extensively characterize the nature of this cluster. Under strictly anaerobic conditions after chemical reconstitution, we demonstrate that EcFeoC binds a redox-active [4Fe-4S]2+/+ cluster that is rapidly oxygen-sensitive and decays to a [2Fe-2S]2+ cluster (t1/2 ≈ 20 s), similar to the [Fe-S] cluster in the fumarate and nitrate reductase (FNR) transcriptional regulator. We further show that this behavior is nearly identical to the homologous K. pneumoniae FeoC, suggesting a redox-active, oxygen-sensitive [4Fe-4S]2+ cofactor is a general phenomenon of cluster-binding FeoCs. Finally, in contrast to FNR, we show that the [4Fe-4S]2+ cluster binding to FeoC is associated with modest conformational changes of the polypeptide, but not protein dimerization. We thus posit a working hypothesis in which the cluster-binding FeoCs may function as oxygen-sensitive iron sensors that fine-tune pathogenic ferrous iron acquisition.
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Affiliation(s)
- Aaron T Smith
- Department of Chemistry and Biochemistry , University of Maryland, Baltimore County , Baltimore , Maryland 21250 United States
| | - Richard O Linkous
- Department of Chemistry and Biochemistry , University of Maryland, Baltimore County , Baltimore , Maryland 21250 United States
| | - Nathan J Max
- Department of Chemistry and Biochemistry , University of Maryland, Baltimore County , Baltimore , Maryland 21250 United States
| | - Alexandrea E Sestok
- Department of Chemistry and Biochemistry , University of Maryland, Baltimore County , Baltimore , Maryland 21250 United States
| | - Veronika A Szalai
- Physical Measurement Laboratory , National Institute of Standards and Technology , Gaithersburg , Maryland 20899 , United States
| | - Kelly N Chacón
- Department of Chemistry , Reed College , Portland , Oregon 97202 , United States
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Willcocks SJ, Stabler RA, Atkins HS, Oyston PF, Wren BW. High-throughput analysis of Yersinia pseudotuberculosis gene essentiality in optimised in vitro conditions, and implications for the speciation of Yersinia pestis. BMC Microbiol 2018; 18:46. [PMID: 29855259 PMCID: PMC5984423 DOI: 10.1186/s12866-018-1189-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 05/18/2018] [Indexed: 12/12/2022] Open
Abstract
Background Yersinia pseudotuberculosis is a zoonotic pathogen, causing mild gastrointestinal infection in humans. From this comparatively benign pathogenic species emerged the highly virulent plague bacillus, Yersinia pestis, which has experienced significant genetic divergence in a relatively short time span. Much of our knowledge of Yersinia spp. evolution stems from genomic comparison and gene expression studies. Here we apply transposon-directed insertion site sequencing (TraDIS) to describe the essential gene set of Y. pseudotuberculosis IP32953 in optimised in vitro growth conditions, and contrast these with the published essential genes of Y. pestis. Results The essential genes of an organism are the core genetic elements required for basic survival processes in a given growth condition, and are therefore attractive targets for antimicrobials. One such gene we identified is yptb3665, which encodes a peptide deformylase, and here we report for the first time, the sensitivity of Y. pseudotuberculosis to actinonin, a deformylase inhibitor. Comparison of the essential genes of Y. pseudotuberculosis with those of Y. pestis revealed the genes whose importance are shared by both species, as well as genes that were differentially required for growth. In particular, we find that the two species uniquely rely upon different iron acquisition and respiratory metabolic pathways under similar in vitro conditions. Conclusions The discovery of uniquely essential genes between the closely related Yersinia spp. represent some of the fundamental, species-defining points of divergence that arose during the evolution of Y. pestis from its ancestor. Furthermore, the shared essential genes represent ideal candidates for the development of novel antimicrobials against both species. Electronic supplementary material The online version of this article (10.1186/s12866-018-1189-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Samuel J Willcocks
- Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| | - Richard A Stabler
- Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| | - Helen S Atkins
- Microbiology, CBR Division, DSTL Porton Down, Salisbury, SP4 0JQ, UK
| | - Petra F Oyston
- Microbiology, CBR Division, DSTL Porton Down, Salisbury, SP4 0JQ, UK
| | - Brendan W Wren
- Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK.
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Schwiesow L, Mettert E, Wei Y, Miller HK, Herrera NG, Balderas D, Kiley PJ, Auerbuch V. Control of hmu Heme Uptake Genes in Yersinia pseudotuberculosis in Response to Iron Sources. Front Cell Infect Microbiol 2018. [PMID: 29520342 PMCID: PMC5827684 DOI: 10.3389/fcimb.2018.00047] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Despite the mammalian host actively sequestering iron to limit pathogenicity, heme (or hemin when oxidized) and hemoproteins serve as important sources of iron for many bloodborne pathogens. The HmuRSTUV hemin uptake system allows Yersinia species to uptake and utilize hemin and hemoproteins as iron sources. HmuR is a TonB-dependent outer membrane receptor for hemin and hemoproteins. HmuTUV comprise a inner membrane ABC transporter that transports hemin and hemoproteins from the periplasmic space into the bacterial cytoplasm, where it is degraded by HmuS. Here we show that hmuSTUV but not hmuR are expressed under iron replete conditions, whereas hmuR as well as hmuSTUV are expressed under iron limiting conditions, suggesting complex transcriptional control. Indeed, expression of hmuSTUV in the presence of inorganic iron, but not in the presence of hemin, requires the global regulator IscR acting from a promoter in the intergenic region between hmuR and hmuS. This effect of IscR appears to be direct by binding a site mapped by DNaseI footprinting. In contrast, expression of hmuR under iron limiting conditions requires derepression of the ferric uptake regulator Fur acting from the hmuR promoter, as Fur binding upstream of hmuR was demonstrated biochemically. Differential expression by both Fur and IscR would facilitate maximal hemin uptake and utilization when iron and heme availability is low while maintaining the capacity for periplasmic removal and cytosolic detoxification of heme under a wider variety of conditions. We also demonstrate that a Y. pseudotuberculosis ΔiscR mutant has a survival defect when incubated in whole blood, in which iron is sequestered by heme-containing proteins. Surprisingly, this phenotype was independent of the Hmu system, the type III secretion system, complement, and the ability of Yersinia to replicate intracellularly. These results suggest that IscR regulates multiple virulence factors important for Yersinia survival and growth in mammalian tissues and reveal a surprising complexity of heme uptake expression and function under differing conditions of iron.
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Affiliation(s)
- Leah Schwiesow
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - Erin Mettert
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI, United States
| | - Yahan Wei
- Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - Halie K Miller
- Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - Natalia G Herrera
- Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - David Balderas
- Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - Patricia J Kiley
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI, United States
| | - Victoria Auerbuch
- Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, Santa Cruz, CA, United States
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