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Liao CH, Lu HF, Yang CW, Yeh TY, Lin YT, Yang TC. HemU and TonB1 contribute to hemin acquisition in Stenotrophomonas maltophilia. Front Cell Infect Microbiol 2024; 14:1380976. [PMID: 38596648 PMCID: PMC11002078 DOI: 10.3389/fcimb.2024.1380976] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Accepted: 03/12/2024] [Indexed: 04/11/2024] Open
Abstract
Introduction The hemin acquisition system is composed of an outer membrane TonB-dependent transporter that internalizes hemin into the periplasm, periplasmic hemin-binding proteins to shuttle hemin, an inner membrane transporter that transports hemin into the cytoplasm, and cytoplasmic heme oxygenase to release iron. Fur and HemP are two known regulators involved in the regulation of hemin acquisition. The hemin acquisition system of Stenotrophomonas maltophilia is poorly understood, with the exception of HemA as a TonB-dependent transporter for hemin uptake. Methods Putative candidates responsible for hemin acquisition were selected via a homolog search and a whole-genome survey of S. maltophilia. Operon verification was performed by reverse transcription-polymerase chain reaction. The involvement of candidate genes in hemin acquisition was assessed using an in-frame deletion mutant construct and iron utilization assays. The transcript levels of candidate genes were determined using quantitative polymerase chain reaction. Results Smlt3896-hemU-exbB2-exbD2-tonB2 and tonB1-exbB1-exbD1a-exbD1b operons were selected as candidates for hemin acquisition. Compared with the parental strain, hemU and tonB1 mutants displayed a defect in their ability to use hemin as the sole iron source for growth. However, hemin utilization by the Smlt3896 and tonB2 mutants was comparable to that of the parental strain. HemA expression was repressed by Fur in iron-replete conditions and derepressed in iron-depleted conditions. HemP negatively regulated hemA expression. Like hemA, hemU was repressed by Fur in iron-replete conditions; however, hemU was moderately derepressed in response to iron-depleted stress and fully derepressed when hemin was present. Unlike hemA and hemU, the TonB1-exbB1-exbD1a-exbD1b operon was constitutively expressed, regardless of the iron level or the presence of hemin, and Fur and HemP had no influence on its expression. Conclusion HemA, HemU, and TonB1 contribute to hemin acquisition in S. maltophilia. Fur represses the expression of hemA and hemU in iron-replete conditions. HemA expression is regulated by low iron levels, and HemP acts as a negative regulator of this regulatory circuit. HemU expression is regulated by low iron and hemin levels in a hemP-dependent manner.
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Affiliation(s)
- Chun-Hsing Liao
- Division of Infectious Disease, Far Eastern Memorial Hospital, New Taipei City, Taiwan
- Department of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Hsu-Feng Lu
- Department of Medical Laboratory Science and Biotechnology, Asia University, Taichung, Taiwan
| | - Ching-Wei Yang
- Department of Biotechnology and Laboratory Science in Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Ting-Yu Yeh
- Department of Biotechnology and Laboratory Science in Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Yi-Tsung Lin
- Division of Infectious Diseases, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
- School of Medicine, National Yang Chiao Tung University, Taipei, Taiwan
| | - Tsuey-Ching Yang
- Department of Biotechnology and Laboratory Science in Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
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2
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Yan YF, Liu Y, Liang H, Cai L, Yang XY, Yin TP. The erythromycin polyketide compound TMC-154 stimulates ROS generation to exert antibacterial effects against Streptococcus pyogenes. J Proteomics 2024; 292:105057. [PMID: 38043864 DOI: 10.1016/j.jprot.2023.105057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 11/07/2023] [Accepted: 11/27/2023] [Indexed: 12/05/2023]
Abstract
The erythromycin polyketide compound TMC-154 is a secondary metabolite that is isolated from the rhizospheric fungus Clonostachys rogersoniana associated with Panax notoginseng, which possesses antibacterial activity. However, its antibacterial mechanism has not been investigated thus far. In this study, proteomics coupled with bioinformatics approaches was used to explore the antibacterial mechanism of TMC-154. KEGG pathway enrichment analysis indicated that eight signaling pathways were associated with TMC-154, including oxidative phosphorylation, cationic antimicrobial peptide (CAMP) resistance, benzoate degradation, heme acquisition systems, glycine/serine and threonine metabolism, beta-lactam resistance, ascorbate and aldarate metabolism, and phosphotransferase system (PTS). Cell biology experiments confirmed that TMC-154 could induce reactive oxygen species (ROS) generation in Streptococcus pyogenes; moreover, TMC-154-induced antibacterial effects could be blocked by the inhibition of ROS generation with the antioxidant N-acetyl L-cysteine. In addition, TMC-154 combined with ciprofloxacin or chloramphenicol had synergistic antibacterial effects. These findings indicate the potential of TMC-154 as a promising drug to treat S. pyogenes infections. SIGNIFICANCE: Streptococcus pyogenes is a nearly ubiquitous human pathogen that causes a variety of diseases ranging from mild pharyngitis and skin infection to fatal sepsis and toxic heat shock syndrome. With the increasing incidence of known antibiotic resistance, there is an urgent need to find novel drugs with good antibacterial activity against S. pyogenes. In this study, we found that TMC-154, a secondary metabolite from the fungus Clonostachys rogersoniana, inhibited the growth of various bacteria, including Staphylococcus aureus, S. pyogenes, Streptococcus mutans, Pseudomonas aeruginosa and Vibrio parahemolyticus. Proteomic analysis combined with cell biology experiments revealed that TMC-154 stimulated ROS generation to exert antibacterial effects against S. pyogenes. This study provides potential options for the treatment of S. pyogenes infections in the future.
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Affiliation(s)
- Yuan-Feng Yan
- School of Bioengineering, Zhuhai Campus of Zunyi Medical University, Zhuhai, Guangdong 519041, China
| | - Ying Liu
- School of Bioengineering, Zhuhai Campus of Zunyi Medical University, Zhuhai, Guangdong 519041, China
| | - Hangeri Liang
- School of Bioengineering, Zhuhai Campus of Zunyi Medical University, Zhuhai, Guangdong 519041, China
| | - Le Cai
- Key Laboratory of Medicinal Chemistry for Natural Resource, Ministry of Education, Yunnan Characteristic Plant Extraction Laboratory, Functional Molecules Analysis and Biotransformation Key Laboratory of Universities in Yunnan Province, School of Chemical Science and Technology, Yunnan University, Kunming 650091, China
| | - Xiao-Yan Yang
- School of Bioengineering, Zhuhai Campus of Zunyi Medical University, Zhuhai, Guangdong 519041, China.
| | - Tian-Peng Yin
- School of Bioengineering, Zhuhai Campus of Zunyi Medical University, Zhuhai, Guangdong 519041, China.
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3
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Brimberry M, Corrigan P, Silakov A, Lanzilotta WN. Evidence for Porphyrin-Mediated Electron Transfer in the Radical SAM Enzyme HutW. Biochemistry 2023; 62:1191-1196. [PMID: 36877586 PMCID: PMC10035031 DOI: 10.1021/acs.biochem.2c00474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
Abstract
Bacteria that infect the human gut must compete for essential nutrients, including iron, under a variety of different metabolic conditions. Several enteric pathogens, including Vibrio cholerae and Escherichia coli O157:H7, have evolved mechanisms to obtain iron from heme in an anaerobic environment. Our laboratory has demonstrated that a radical S-adenosylmethionine (SAM) methyltransferase is responsible for the opening of the heme porphyrin ring and release of iron under anaerobic conditions. Furthermore, the enzyme in V. cholerae, HutW, has recently been shown to accept electrons from NADPH directly when SAM is utilized to initiate the reaction. However, how NADPH, a hydride donor, catalyzes the single electron reduction of a [4Fe-4S] cluster, and/or subsequent electron/proton transfer reactions, was not addressed. In this work, we provide evidence that the substrate, in this case, heme, facilitates electron transfer from NADPH to the [4Fe-4S] cluster. This study uncovers a new electron transfer pathway adopted by radical SAM enzymes and further expands our understanding of these enzymes in bacterial pathogens.
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Affiliation(s)
- Marley Brimberry
- Department of Biochemistry and Molecular Biology & Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602, United States
| | - Patrick Corrigan
- Department of Chemistry, Penn State University, University Park, Pennsylvania 16802, United States
| | - Alexey Silakov
- Department of Chemistry, Penn State University, University Park, Pennsylvania 16802, United States
| | - William N Lanzilotta
- Department of Biochemistry and Molecular Biology & Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602, United States
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4
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Dong J, Sun C, Tian Y, Zhang H, Liu Z, Gao F, Ye X. Genomic organization and gene evolution of two warm temperature acclimation proteins (Wap65s) of Micropterus salmoides and their responses to temperature and bacterial/viral infections. Int J Biol Macromol 2023; 227:340-353. [PMID: 36529221 DOI: 10.1016/j.ijbiomac.2022.12.065] [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: 10/10/2022] [Revised: 11/23/2022] [Accepted: 12/06/2022] [Indexed: 12/23/2022]
Abstract
Warm temperature acclimation-related 65-kDa proteins (Wap65s) are fish plasma acute-phase glycoproteins homologous to hemopexin with high affinity and clearance for heme. The study characterized Mswap65-1 and Mswap65-2 genes in Micropterus salmoides. Structural analysis showed MsWap65s contained conserved heme-binding sites. MsWap65-1 had a chloride-binding site similar to hemopexin, while MsWap65-2 had an additional calcium-binding site. Phylogenetic and Ka/Ks analysis showed that fish Wap65s were evolutionarily conserved and underwent strong purifying selection. Functional divergence analysis indicated that fish Wap65-2 retained the putative function of ancestral Wap65, while Wap65-1 underwent neofunctional differentiation. QPCR showed Mswap65s were predominantly expressed in liver, but prolonged hyperthermy inhibited Mswap65-2 expression. Mswap65-2 expression was up-regulated in liver and spleen after Nocardia seriolae infection, while Mswap65-1 was down-regulated. MsWap65-2 may be associated with pathogenesis and play potential role in pathogen resistance. LMBV infection resulted in both significant downregulation of Mswap65s were both significantly down-regulated, with differences observed between sexes. We speculated the immune system might suppress expression after viral infection. Exogenous rMsWap65s were prepared, and injection of rMsWap65s alleviated phenylhydrazine-induced hemolysis and inhibited increases in heme, complement C3 and inflammatory symptoms. Our results contribute to an advanced understanding of the functions and mechanisms of MsWap65s in stress resistance.
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Affiliation(s)
- Junjian Dong
- Key Laboratory of Tropical and Subtropical Fisheries Resource Application and Cultivation, Ministry of Agriculture and Rural Affairs, Pearl River Fisheries Institute, Chinese Academy of Fishery Sciences, Guangzhou, China; Key Laboratory of Aquatic Animal Immune Technology of Guangdong Province, Pearl River Fisheries Institute, Chinese Academy of Fishery Sciences, Guangzhou, China
| | - Chengfei Sun
- Key Laboratory of Tropical and Subtropical Fisheries Resource Application and Cultivation, Ministry of Agriculture and Rural Affairs, Pearl River Fisheries Institute, Chinese Academy of Fishery Sciences, Guangzhou, China; Key Laboratory of Aquatic Animal Immune Technology of Guangdong Province, Pearl River Fisheries Institute, Chinese Academy of Fishery Sciences, Guangzhou, China
| | - Yuanyuan Tian
- Key Laboratory of Tropical and Subtropical Fisheries Resource Application and Cultivation, Ministry of Agriculture and Rural Affairs, Pearl River Fisheries Institute, Chinese Academy of Fishery Sciences, Guangzhou, China; Key Laboratory of Aquatic Animal Immune Technology of Guangdong Province, Pearl River Fisheries Institute, Chinese Academy of Fishery Sciences, Guangzhou, China
| | - Hetong Zhang
- Key Laboratory of Tropical and Subtropical Fisheries Resource Application and Cultivation, Ministry of Agriculture and Rural Affairs, Pearl River Fisheries Institute, Chinese Academy of Fishery Sciences, Guangzhou, China; Key Laboratory of Aquatic Animal Immune Technology of Guangdong Province, Pearl River Fisheries Institute, Chinese Academy of Fishery Sciences, Guangzhou, China
| | - Zhigang Liu
- Key Laboratory of Tropical and Subtropical Fisheries Resource Application and Cultivation, Ministry of Agriculture and Rural Affairs, Pearl River Fisheries Institute, Chinese Academy of Fishery Sciences, Guangzhou, China; Key Laboratory of Aquatic Animal Immune Technology of Guangdong Province, Pearl River Fisheries Institute, Chinese Academy of Fishery Sciences, Guangzhou, China; College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, China
| | - Fengying Gao
- Key Laboratory of Tropical and Subtropical Fisheries Resource Application and Cultivation, Ministry of Agriculture and Rural Affairs, Pearl River Fisheries Institute, Chinese Academy of Fishery Sciences, Guangzhou, China; Key Laboratory of Aquatic Animal Immune Technology of Guangdong Province, Pearl River Fisheries Institute, Chinese Academy of Fishery Sciences, Guangzhou, China; College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, China.
| | - Xing Ye
- Key Laboratory of Tropical and Subtropical Fisheries Resource Application and Cultivation, Ministry of Agriculture and Rural Affairs, Pearl River Fisheries Institute, Chinese Academy of Fishery Sciences, Guangzhou, China; Key Laboratory of Aquatic Animal Immune Technology of Guangdong Province, Pearl River Fisheries Institute, Chinese Academy of Fishery Sciences, Guangzhou, China; College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, China.
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5
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Purdie AC, Plain KM, Pooley H, Begg DJ, de Silva K, Whittington RJ. Correlates of vaccine protection against Mycobacterium avium sub-species paratuberculosis infection revealed in a transcriptomic study of responses in Gudair ® vaccinated sheep. Front Vet Sci 2022; 9:1004237. [PMID: 36504842 PMCID: PMC9729357 DOI: 10.3389/fvets.2022.1004237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Accepted: 11/07/2022] [Indexed: 11/25/2022] Open
Abstract
A critical hindrance in the development of effective vaccine strategies to combat infectious disease is lack of knowledge about correlates of protection and of the host responses necessary for successful adaptive immunity. Often vaccine formulations are developed by stepwise experimentation, with incomplete investigation of the fundamental mechanisms of protection. Gudair® is a commercially available vaccine registered for use in sheep and goats for controlling spread of Mycobacterium avium sub-species paratuberculosis (MAP) infections and reduces mortality by up to 90%. Here, using an experimental infection model in sheep, we have utilized a transcriptomics approach to identify white blood cell gene expression changes in vaccinated, MAP-exposed Merino sheep with a protective response in comparison to those vaccinated animals that failed to develop immunity to MAP infection. This methodology facilitated an overview of gene-associated functional pathway adaptations using an in-silico analysis approach. We identified a group of genes that were activated in the vaccine-protected animals and confirmed stability of expression in samples obtained from naturally exposed commercially maintained sheep. We propose these genes as correlates of vaccine induced protection.
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6
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Zafar W, Sumrra SH, Chohan ZH. A review: Pharmacological aspects of metal based 1,2,4-triazole derived Schiff bases. Eur J Med Chem 2021; 222:113602. [PMID: 34139626 DOI: 10.1016/j.ejmech.2021.113602] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Revised: 05/06/2021] [Accepted: 06/01/2021] [Indexed: 12/19/2022]
Abstract
Clinical reports have highlighted the radical increase of antibiotic resistance. As a result, multidrug resistance has emerged as a serious threat to human health. Many organic compounds commonly used as drugs in the past, no longer have pure organic mode of action rather need bio-transformation or more activation. Bulk of research has shown that they need trace amount of metal ions incorporated within the chemistry of bioactive molecules for enhancement of their potentiality to fight aggressively against resistance. The deficiency of some metal ions can also be responsible for many diseases like growth retardation, pernicious anemia and heart diseases in infants. To overcome these problems, there is a need to introduce novel strategies which have new mechanism of action along with significant spectrum of biological activity, enhanced safety and efficacy. Bioinorganic compounds have played imperative role in developing the new strategy in the form of "Metal Based Drugs". In current years there have been momentous rise of interest in the application of metal based Schiff base compounds to treat various diseases which are difficult to be treated with conventional methodologies. The unique properties of metal chelates acting as an intermediate between conventional organic and inorganic compounds provided innovative opportunities in the field of pharmaceutical chemistry. In this review, we have exclusively focused on the search of metal based 1,2,4-triazole derived Schiff base compounds (synthesized, reported and reviewed in the past ten years) that possess various biological activities such as antifungal, antibacterial, antioxidant, antidiabetic, anthelmintic, anticancer, antiproliferative, cytotoxic and DNA-intercalation activity.
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Affiliation(s)
- Wardha Zafar
- Department of Chemistry, University of Gujrat, Gujrat, 50700, Pakistan
| | - Sajjad H Sumrra
- Department of Chemistry, University of Gujrat, Gujrat, 50700, Pakistan.
| | - Zahid H Chohan
- Department of Chemistry, Institute of Southern Punjab, Multan, Pakistan
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7
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Sun Q, Huang M, Wei Y. Diversity of the reaction mechanisms of SAM-dependent enzymes. Acta Pharm Sin B 2021; 11:632-650. [PMID: 33777672 PMCID: PMC7982431 DOI: 10.1016/j.apsb.2020.08.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 07/30/2020] [Accepted: 08/08/2020] [Indexed: 02/08/2023] Open
Abstract
S-adenosylmethionine (SAM) is ubiquitous in living organisms and is of great significance in metabolism as a cofactor of various enzymes. Methyltransferases (MTases), a major group of SAM-dependent enzymes, catalyze methyl transfer from SAM to C, O, N, and S atoms in small-molecule secondary metabolites and macromolecules, including proteins and nucleic acids. MTases have long been a hot topic in biomedical research because of their crucial role in epigenetic regulation of macromolecules and biosynthesis of natural products with prolific pharmacological moieties. However, another group of SAM-dependent enzymes, sharing similar core domains with MTases, can catalyze nonmethylation reactions and have multiple functions. Herein, we mainly describe the nonmethylation reactions of SAM-dependent enzymes in biosynthesis. First, we compare the structural and mechanistic similarities and distinctions between SAM-dependent MTases and the non-methylating SAM-dependent enzymes. Second, we summarize the reactions catalyzed by these enzymes and explore the mechanisms. Finally, we discuss the structural conservation and catalytical diversity of class I-like non-methylating SAM-dependent enzymes and propose a possibility in enzymes evolution, suggesting future perspectives for enzyme-mediated chemistry and biotechnology, which will help the development of new methods for drug synthesis.
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8
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Brimberry M, Toma MA, Hines KM, Lanzilotta WN. HutW from Vibrio cholerae Is an Anaerobic Heme-Degrading Enzyme with Unique Functional Properties. Biochemistry 2021; 60:699-710. [PMID: 33600151 DOI: 10.1021/acs.biochem.0c00950] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Increasing antibiotic resistance, and a growing recognition of the importance of the human microbiome, demand that new therapeutic targets be identified. Characterization of metabolic pathways that are unique to enteric pathogens represents a promising approach. Iron is often the rate-limiting factor for growth, and Vibrio cholerae, the causative agent of cholera, has been shown to contain numerous genes that function in the acquisition of iron from the environment. Included in this arsenal of genes are operons dedicated to obtaining iron from heme and heme-containing proteins. Given the persistence of cholera, an important outstanding question is whether V. cholerae is capable of anaerobic heme degradation as was recently reported for enterohemorrhagic Escherichia coli O157:H7. In this work, we demonstrate that HutW from V. cholerae is a radical S-adenosylmethionine methyl transferase involved in the anaerobic opening of the porphyrin ring of heme. However, in contrast to the enzyme ChuW, found in enterohemorrhagic E. coli O157:H7, there are notable differences in the mechanism and products of the HutW reaction. Of particular interest are data that demonstrate HutW will catalyze ring opening as well as tetrapyrrole reduction and can utilize reduced nicotinamide adenine dinucleotide phosphate as an electron source. The biochemical and biophysical properties of HutW are presented, and the evolutionary implications are discussed.
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9
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Khan D, Lee D, Gulten G, Aggarwal A, Wofford J, Krieger I, Tripathi A, Patrick JW, Eckert DM, Laganowsky A, Sacchettini J, Lindahl P, Bankaitis VA. A Sec14-like phosphatidylinositol transfer protein paralog defines a novel class of heme-binding proteins. eLife 2020; 9:57081. [PMID: 32780017 PMCID: PMC7462610 DOI: 10.7554/elife.57081] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 08/10/2020] [Indexed: 01/02/2023] Open
Abstract
Yeast Sfh5 is an unusual member of the Sec14-like phosphatidylinositol transfer protein (PITP) family. Whereas PITPs are defined by their abilities to transfer phosphatidylinositol between membranes in vitro, and to stimulate phosphoinositide signaling in vivo, Sfh5 does not exhibit these activities. Rather, Sfh5 is a redox-active penta-coordinate high spin FeIII hemoprotein with an unusual heme-binding arrangement that involves a co-axial tyrosine/histidine coordination strategy and a complex electronic structure connecting the open shell iron d-orbitals with three aromatic ring systems. That Sfh5 is not a PITP is supported by demonstrations that heme is not a readily exchangeable ligand, and that phosphatidylinositol-exchange activity is resuscitated in heme binding-deficient Sfh5 mutants. The collective data identify Sfh5 as the prototype of a new class of fungal hemoproteins, and emphasize the versatility of the Sec14-fold as scaffold for translating the binding of chemically distinct ligands to the control of diverse sets of cellular activities.
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Affiliation(s)
- Danish Khan
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, United States
| | - Dongju Lee
- Department of Molecular and Cellular Medicine, Texas A&M Health Sciences Center, College Station, United States
| | - Gulcin Gulten
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, United States
| | - Anup Aggarwal
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, United States
| | - Joshua Wofford
- Department of Chemistry, Texas A&M University, College Station, United States.,Department of Chemistry, Charleston Southern University, North Charleston, United States
| | - Inna Krieger
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, United States
| | - Ashutosh Tripathi
- Department of Molecular and Cellular Medicine, Texas A&M Health Sciences Center, College Station, United States
| | - John W Patrick
- Department of Chemistry, Texas A&M University, College Station, United States
| | - Debra M Eckert
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, United States
| | - Arthur Laganowsky
- Department of Chemistry, Texas A&M University, College Station, United States
| | - James Sacchettini
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, United States
| | - Paul Lindahl
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, United States.,Department of Chemistry, Texas A&M University, College Station, United States
| | - Vytas A Bankaitis
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, United States.,Department of Molecular and Cellular Medicine, Texas A&M Health Sciences Center, College Station, United States.,Department of Chemistry, Texas A&M University, College Station, United States
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10
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Yuan C, Zhang Y, Tan H, Li X, Chen G, Jia Z. ONIOM investigations of the heme degradation mechanism by MhuD: the critical function of heme ruffling. Phys Chem Chem Phys 2020; 22:8817-8826. [DOI: 10.1039/c9cp05868k] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A unique ruffling conformation of hydroxyheme in MhuD inhibits its “on-site” monooxygenation but induces “remote-site” dioxygenation.
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Affiliation(s)
- Chang Yuan
- College of Chemistry
- Key Laboratories of Theoretical and Computational Photochemistry
- Ministry of Education
- Beijing Normal University
- Beijing
| | - Ying Zhang
- College of Chemistry
- Key Laboratories of Theoretical and Computational Photochemistry
- Ministry of Education
- Beijing Normal University
- Beijing
| | - Hongwei Tan
- College of Chemistry
- Key Laboratories of Theoretical and Computational Photochemistry
- Ministry of Education
- Beijing Normal University
- Beijing
| | - Xichen Li
- College of Chemistry
- Key Laboratories of Theoretical and Computational Photochemistry
- Ministry of Education
- Beijing Normal University
- Beijing
| | - Guangju Chen
- College of Chemistry
- Key Laboratories of Theoretical and Computational Photochemistry
- Ministry of Education
- Beijing Normal University
- Beijing
| | - Zongchao Jia
- Department of Biomedical and Molecular Sciences
- Queen's University
- Kingston
- Ontario
- Canada
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11
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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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12
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Dojun N, Muranishi K, Ishimori K, Uchida T. A single mutation converts Alr5027 from cyanobacteria Nostoc sp. PCC 7120 to a heme-binding protein with heme-degrading ability. J Inorg Biochem 2019; 203:110916. [PMID: 31739124 DOI: 10.1016/j.jinorgbio.2019.110916] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 10/25/2019] [Accepted: 11/08/2019] [Indexed: 11/19/2022]
Abstract
HutZ from Vibrio cholerae (VcHutZ) is a dimeric protein that catalyzes oxygen-dependent degradation of heme. The reaction mechanism is the same as that of canonical heme oxygenase (HO), but the structure of HutZ is quite different from that of HO. Thus, we postulate that HutZ has evolved via a different pathway from that of HO. The Alr5027 protein from cyanobacteria possessing proteins potentially related to ancestral proteins utilizing O2 in enzymatic reactions is homologous to HutZ family proteins (67% similarity), but the heme axial ligand of HutZ is not conserved in Alr5027. To investigate whether Alr5027 can bind and degrade heme, we expressed Alr5027 in Escherichia coli and purified it. Although Alr5027 did not bind heme, replacement of Lys164, corresponding to the heme axial ligand of HutZ, with histidine conferred heme-binding capability. The K164H mutant produced verdoheme in the reaction with H2O2, indicating acquisition of heme-degradation ability. Among the mutants, the K164H mutant produced verdoheme most efficiently. Although the K164H mutant did not degrade heme through ascorbic acid, biliverdin, the final product of VcHutZ, was formed by treatment of verdoheme with ascorbic acid. An analysis of Trp103 fluorescence indicated elongation of the distance between protomers in this mutant compared with VcHutZ-the probable cause of the inefficiency of ascorbic acid-supported heme-degradation activity. Collectively, our findings indicate that a single lysine-to-histidine mutation converted Alr5027 to a heme-binding protein that can form verdoheme through H2O2, suggesting that HutZ family proteins have acquired the heme-degradation function through molecular evolution from an ancestor protein of Alr5027.
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Affiliation(s)
- Nobuhiko Dojun
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-8628, Japan
| | - Kazuyoshi Muranishi
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-8628, Japan
| | - Koichiro Ishimori
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-8628, Japan; Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Takeshi Uchida
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-8628, Japan; Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan.
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13
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Uchida T, Dojun N, Ota K, Sekine Y, Nakamura Y, Umetsu S, Ishimori K. Role of conserved arginine in the heme distal site of HutZ from Vibrio cholerae in the heme degradation reaction. Arch Biochem Biophys 2019; 677:108165. [PMID: 31689379 DOI: 10.1016/j.abb.2019.108165] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 10/25/2019] [Accepted: 10/30/2019] [Indexed: 10/25/2022]
Abstract
HutZ from Vibrio cholerae is a dimeric enzyme that catalyzes degradation of heme. The highly conserved Arg92 residue in the HutZ family is proposed to interact with an iron-bound water molecule in the distal heme pocket. To clarify the specific role of Arg92 in the heme degradation reaction, the residue was substituted with alanine, leucine, histidine or lysine to modulate electrostatic interactions with iron-bound ligand. All four Arg92 mutants reacted with hydrogen peroxide to form verdoheme, a prominent intermediate in the heme degradation process. However, when ascorbic acid was used as an electron source, iron was not released even at pH 6.0 despite a decrease in the Soret band, indicating that non-enzymatic heme degradation occurred. Comparison of the rates of heme reduction, ligand binding and verdoheme formation suggested that proton transfer to the reduced oxyferrous heme, a potential rate-limiting step of heme degradation in HutZ, is hampered by mutation. In our previous study, we found that the increase in the distance between heme and Trp109 from 16 to 18 Å upon lowering the pH from 8.0 to 6.0 leads to activation of ascorbic acid-assisted heme degradation by HutZ. The distance in Arg92 mutants was >19 Å at pH 6.0, suggesting that subunit-subunit interactions at this pH are not suitable for heme degradation, similar to Asp132 and His63 mutants. These results suggest that interactions of Arg92 with heme-bound ligand induce alterations in the distance between subunits, which plays a key role in controlling the heme degradation activity of HutZ.
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Affiliation(s)
- Takeshi Uchida
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, 060-0810, Japan; Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, 060-8628, Japan.
| | - Nobuhiko Dojun
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Kazuki Ota
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Yukari Sekine
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Yuina Nakamura
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Sayaka Umetsu
- Division of Chemistry, School of Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Koichiro Ishimori
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, 060-0810, Japan; Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, 060-8628, Japan
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14
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Shi YJ, Fang QJ, Huang HQ, Gong CG, Hu YH. HutZ is required for biofilm formation and contributes to the pathogenicity of Edwardsiella piscicida. Vet Res 2019; 50:76. [PMID: 31578154 PMCID: PMC6775658 DOI: 10.1186/s13567-019-0693-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Accepted: 08/19/2019] [Indexed: 12/13/2022] Open
Abstract
Edwardsiella piscicida is a severe fish pathogen. Haem utilization systems play an important role in bacterial adversity adaptation and pathogenicity. In this study, a speculative haem utilization protein, HutZEp, was characterized in E. piscicida. hutZEp is encoded with two other genes, hutW and hutX, in an operon that is similar to the haem utilization operon hutWXZ identified in V. cholerae. However, protein activity analysis showed that HutZEp is probably not related to hemin utilization. To explore the biological role of HutZEp, a markerless hutZEp in-frame mutant strain, TX01ΔhutZ, was constructed. Deletion of hutZEp did not significantly affect bacterial growth in normal medium, in iron-deficient conditions, or in the presence of haem but significantly retarded bacterial biofilm growth. The expression of known genes related to biofilm growth was not affected by hutZEp deletion, which indicated that HutZEp was probably a novel factor promoting biofilm formation in E. piscicida. Compared to the wild-type TX01, TX01ΔhutZ exhibited markedly compromised tolerance to acid stress and host serum stress. Pathogenicity analysis showed that inactivation of hutZEp significantly impaired the ability of E. piscicida to invade and reproduce in host cells and to infect host tissue. In contrast to TX01, TX01ΔhutZ was defective in blocking host macrophage activation. The expression of hutZEp was directly regulated by the ferric uptake regulator Fur. This study is the first functional characterization of HutZ in a fish pathogen, and these findings suggested that HutZEp is essential for E. piscicida biofilm formation and contributes to host infection.
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Affiliation(s)
- Yan-Jie Shi
- Ocean College of Hebei Agricultural University, Qinhuangdao, 066000, China.,Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, China
| | - Qing-Jian Fang
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, China
| | - Hui-Qin Huang
- Ocean College of Hebei Agricultural University, Qinhuangdao, 066000, China.,Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, China.,Hainan Provincial Key Laboratory for Functional Components Research and Utilization of Marine Bio-resources, Haikou, 571101, China
| | - Chun-Guang Gong
- Ocean College of Hebei Agricultural University, Qinhuangdao, 066000, China.
| | - Yong-Hua Hu
- Ocean College of Hebei Agricultural University, Qinhuangdao, 066000, China. .,Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, China. .,Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology, Qingdao, China. .,Hainan Provincial Key Laboratory for Functional Components Research and Utilization of Marine Bio-resources, Haikou, 571101, China.
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15
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Datta S, Kenton RJ. Characterization of temperature-dependent hemin uptake receptors HupA and HvtA in Vibrio vulnificus. Microbiologyopen 2019; 8:e905. [PMID: 31290613 PMCID: PMC6813434 DOI: 10.1002/mbo3.905] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 06/09/2019] [Accepted: 06/24/2019] [Indexed: 12/19/2022] Open
Abstract
The Gram-negative pathogen Vibrio vulnificus produces several iron-sequestration systems including a hemin uptake system in response to iron limitation as a means to acquire this essential element. Strains of this organism are capable of causing serious septicemia in humans and eels, where hemin is abundant and an advantageous source of iron. Vibrio vulnificus hemin uptake systems consist of HupA, a well studied outer membrane protein, and a recently identified HvtA protein receptor. In this study, we confirmed that the expression of the hvtA gene is iron-regulated in a fur-dependent manner. When analyzed for virulence in a hemin-overloaded murine model system, the hupA gene was more important for establishing infection than the hvtA gene. Transcriptional profiling of these genes using strains of two different biotypes, biotype 1 (human pathogen) and biotype 2 (eel pathogen), showed that the expression of the two receptors was also regulated in response to temperature. The expression of hupA was highly induced in elevated temperatures in the human pathogenic strain when tested in iron-depleted conditions. Conversely, hvtA expression was induced significantly in the eel pathogenic strain at a lower temperature, a condition where the hupA locus was relatively repressed. Our results indicate that although both hupA and hvtA are involved for optimal hemin uptake in V. vulnificus, their expression is dually regulated by the environmental cues of iron concentration and temperature. Together, these data suggest that the virulence genes hupA and hvtA are tightly regulated and strictly induced during iron limitation combined with the physiological temperature of the host organism.
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Affiliation(s)
| | - Ryan J. Kenton
- Department of BiologyUniversity of PortlandPortlandORUSA
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16
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Uchida T, Ota K, Sekine Y, Dojun N, Ishimori K. Subunit-subunit interactions play a key role in the heme-degradation reaction of HutZ from Vibrio cholerae. Dalton Trans 2019; 48:3973-3983. [PMID: 30834412 DOI: 10.1039/c9dt00604d] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
HutZ, a dimeric protein, from Vibrio cholerae is a protein that catalyzes the oxygen-dependent degradation of heme. Interestingly, the ascorbic acid-supported heme-degradation activity of HutZ depends on pH: less than 10% of heme is degraded by HutZ at pH 8.0, but nearly 90% of heme is degraded at pH 6.0. We examined here pH-dependent conformational changes in HutZ using fluorescence spectroscopy. Trp109 is estimated to be located approximately 21 Å from heme and is present in a different subunit containing a heme axial ligand. Thus, we postulated that the distance between heme and Trp109 reflects subunit-subunit orientational changes. On the basis of resonance energy transfer from Trp109 to heme, we estimated the distance between heme and Trp109 to be approximately 17 Å at pH 8.0, while the distance increased by less than 2 Å at pH 6.0. We presumed that such changes led to a decrease in electron donation from the proximal histidine, resulting in enhancement of the heme-degradation activity. To confirm this scenario, we mutated Ala31, located at the dimer interface, to valine to alter the distance through the subunit-subunit interaction. The distance between heme and Trp109 for the A31V mutant was elongated to 24-27 Å. Although resonance Raman spectra and reduction rate of heme suggested that this mutation resulted in diminished electron donation from the heme axial ligand, ascorbic acid-supported heme-degradation activity was not observed. Based on our findings, it can be proposed that the relative positioning of two protomers is important in determining the heme degradation rate by HutZ.
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Affiliation(s)
- Takeshi Uchida
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan.
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17
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Electrochemical characterization of Fe center from hemin binding with Yersinia pestis heme-protein acquisition system. Electrochim Acta 2019. [DOI: 10.1016/j.electacta.2018.12.109] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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18
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Osman D, Martini MA, Foster AW, Chen J, Scott AJP, Morton RJ, Steed JW, Lurie-Luke E, Huggins TG, Lawrence AD, Deery E, Warren MJ, Chivers PT, Robinson NJ. Bacterial sensors define intracellular free energies for correct enzyme metalation. Nat Chem Biol 2019; 15:241-249. [PMID: 30692683 PMCID: PMC6420079 DOI: 10.1038/s41589-018-0211-4] [Citation(s) in RCA: 94] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 12/04/2018] [Indexed: 01/06/2023]
Abstract
There is a challenge for metalloenzymes to acquire their correct metals because some inorganic elements form more stable complexes with proteins than do others. These preferences can be overcome provided some metals are more available than others. However, while the total amount of cellular metal can be readily measured, the available levels of each metal have been more difficult to define. Metal-sensing transcriptional regulators are tuned to the intracellular availabilities of their cognate ions. Here we have determined the standard free energy for metal complex formation to which each sensor, in a set of bacterial metal sensors, is attuned: The less competitive the metal, the less favorable the free energy and hence greater availability to which the cognate allosteric mechanism is tuned. Comparing these free energies with values derived from the metal affinities of a metalloprotein reveals the mechanism of correct metalation exemplified here by a cobalt-chelatase for vitamin B12.
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Affiliation(s)
- Deenah Osman
- Department of Biosciences, Durham University, Durham, UK.,Department of Chemistry, Durham University, Durham, UK
| | | | - Andrew W Foster
- Department of Biosciences, Durham University, Durham, UK.,Department of Chemistry, Durham University, Durham, UK
| | - Junjun Chen
- Procter and Gamble, Mason Business Center, Cincinnati, OH, USA
| | | | - Richard J Morton
- Department of Mathematics, Physics and Electrical Engineering, Northumbria University, Newcastle-upon-Tyne, UK
| | | | | | | | | | - Evelyne Deery
- School of Biosciences, University of Kent, Canterbury, Kent, UK
| | - Martin J Warren
- School of Biosciences, University of Kent, Canterbury, Kent, UK
| | - Peter T Chivers
- Department of Biosciences, Durham University, Durham, UK. .,Department of Chemistry, Durham University, Durham, UK.
| | - Nigel J Robinson
- Department of Biosciences, Durham University, Durham, UK. .,Department of Chemistry, Durham University, Durham, UK.
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19
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Dirhodium (II) complex interferes with iron-transport system to exert antibacterial action against Streptococcus pneumoniae. J Proteomics 2018; 194:160-167. [PMID: 30521977 DOI: 10.1016/j.jprot.2018.11.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 11/13/2018] [Accepted: 11/26/2018] [Indexed: 01/03/2023]
Abstract
Drug resistance in bacteria is becoming a significant threat to global public health, and the development of novel and efficient antibacterial compounds is urgently needed. Recently, rhodium complexes have attracted attention as antimicrobial agents, yet their antibacterial mechanism remains unknown. In this study, we observed that the dirhodium (II) complex Rh2Ac4 inhibited Streptococcus. pneumoniae growth without significant cytotoxic side-effects on host cells in vitro. We subsequently investigated the antibacterial mechanism of Rh2Ac4 using iTRAQ-based proteomics combined with cellular and biochemical assays. Bioinformatics analysis on the proteomic alterations demonstrated that six molecular functional groups, including metal ion binding and twelve metabolic pathways, were significantly affected after treatment with Rh2Ac4. The interaction network analysis of metal ion binding proteins suggested that Rh2Ac4 decreased the protein expression levels of SPD_1652, SPD_1590 and Gap, which are associated with haem uptake/metabolism. Cellular and biochemical assays further confirmed that Rh2Ac4 could be taken up by bacteria via the PiuABCD haem-uptake system. The structurally similar Rh complex may compete with Fe-haem to decrease Fe-uptake via the PiuABCD system, disrupting iron metabolism to exert its antibacterial activity against S. pneumoniae. These data indicate that Rh2Ac4 is a promising new drug for the treatment of S. pneumoniae infections.
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20
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Linz B, Mukhtar N, Shabbir MZ, Rivera I, Ivanov YV, Tahir Z, Yaqub T, Harvill ET. Virulent Epidemic Pneumonia in Sheep Caused by the Human Pathogen Acinetobacter baumannii. Front Microbiol 2018; 9:2616. [PMID: 30459734 PMCID: PMC6232368 DOI: 10.3389/fmicb.2018.02616] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 10/12/2018] [Indexed: 01/12/2023] Open
Abstract
The human pathogen Acinetobacter baumannii has emerged as a frequent cause of hospital-acquired infections, but infection of animals has rarely been observed. Here we analyzed an outbreak of epidemic pneumonia killing hundreds of sheep on a farm in Pakistan and identified A. baumannii as the infecting agent. A pure culture of strain AbPK1 isolated from lungs of sick animals was inoculated into healthy sheep, which subsequently developed similar disease symptoms. Bacteria re-isolated from the infected animals were shown to be identical to the inoculum, fulfilling Koch’s postulates. Comparison of the AbPK1 genome against 2283 A. baumannii genomes from the NCBI database revealed that AbPK1 carries genes for unusual surface structures, including a unique composition of iron acquisition genes, genes for O-antigen synthesis and sialic acid-specific acetylases of cell-surface carbohydrates that could enable immune evasion. Several of these unusual and otherwise rarely present genes were also identified in genomes of phylogenetically unrelated A. baumannii isolates from combat-wounded US military from Afghanistan indicating a common gene pool in this geographical region. Based on core genome MLST this virulent isolate represents a newly emerging lineage of Global Clone 2, suggesting a human source for this disease outbreak. The observed epidemic, direct transmission from sheep to sheep, which is highly unusual for A. baumannii, has important consequences for human and animal health. First, direct animal-to-animal transmission facilitates fast spread of pathogen and disease in the flock. Second, it may establish a stable ecological niche and subsequent spread in a new host. And third, it constitutes a serious risk of transmission of this hyper-virulent clone from sheep back to humans, which may result in emergence of contagious disease amongst humans.
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Affiliation(s)
- Bodo Linz
- Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA, United States.,Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
| | - Nadia Mukhtar
- Quality Operations Laboratory, University of Veterinary and Animal Sciences, Lahore, Pakistan
| | - Muhammad Zubair Shabbir
- Quality Operations Laboratory, University of Veterinary and Animal Sciences, Lahore, Pakistan
| | - Israel Rivera
- Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA, United States.,Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
| | - Yury V Ivanov
- Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA, United States
| | - Zarfishan Tahir
- Quality Operations Laboratory, University of Veterinary and Animal Sciences, Lahore, Pakistan
| | - Tahir Yaqub
- Quality Operations Laboratory, University of Veterinary and Animal Sciences, Lahore, Pakistan
| | - Eric T Harvill
- Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA, United States.,Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
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21
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Li B, Bridwell-Rabb J. Aerobic Enzymes and Their Radical SAM Enzyme Counterparts in Tetrapyrrole Pathways. Biochemistry 2018; 58:85-93. [PMID: 30365306 DOI: 10.1021/acs.biochem.8b00906] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Microorganisms have lifestyles and metabolism adapted to environmental niches, which can be very broad or highly restricted. Molecular oxygen (O2) is currently variably present in microenvironments and has driven adaptation and microbial differentiation over the course of evolution on Earth. Obligate anaerobes use enzymes and cofactors susceptible to low levels of O2 and are restricted to O2-free environments, whereas aerobes typically take advantage of O2 as a reactant in many biochemical pathways and may require O2 for essential biochemical reactions. In this Perspective, we focus on analogous enzymes found in tetrapyrrole biosynthesis, modification, and degradation that are catalyzed by O2-sensitive radical S-adenosylmethionine (SAM) enzymes and by O2-dependent metalloenzymes. We showcase four transformations for which aerobic organisms use O2 as a cosubstrate but anaerobic organisms do not. These reactions include oxidative decarboxylation, methyl and methylene oxidation, ring formation, and ring cleavage. Furthermore, we highlight biochemically uncharacterized enzymes implicated in reactions that resemble those catalyzed by the parallel aerobic and anaerobic enzymes. Intriguingly, several of these reactions require insertion of an oxygen atom into the substrate, which in aerobic enzymes is facilitated by activation of O2 but in anaerobic organisms requires an alternative mechanism.
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Affiliation(s)
- Bin Li
- Department of Chemistry , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - Jennifer Bridwell-Rabb
- Department of Chemistry , University of Michigan , Ann Arbor , Michigan 48109 , United States
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22
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Eshelman K, Yao H, Punchi Hewage AND, Deay JJ, Chandler JR, Rivera M. Inhibiting the BfrB:Bfd interaction in Pseudomonas aeruginosa causes irreversible iron accumulation in bacterioferritin and iron deficiency in the bacterial cytosol. Metallomics 2018; 9:646-659. [PMID: 28318006 DOI: 10.1039/c7mt00042a] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Iron is an essential nutrient for bacteria but the reactivity of Fe2+ and the insolubility of Fe3+ present significant challenges to bacterial cells. Iron storage proteins contribute to ameliorating these challenges by oxidizing Fe2+ using O2 and H2O2 as electron acceptors, and by compartmentalizing Fe3+. Two types of iron-storage proteins coexist in bacteria, the ferritins (Ftn) and the heme-containing bacterioferritins (Bfr), but the reasons for their coexistence are largely unknown. P. aeruginosa cells harbor two iron storage proteins (FtnA and BfrB), but nothing is known about their relative contributions to iron homeostasis. Prior studies in vitro have shown that iron mobilization from BfrB requires specific interactions with a ferredoxin (Bfd), but the relevance of the BfrB:Bfd interaction to iron homeostasis in P. aeruginosa is unknown. In this work we explore the repercussions of (i) deleting the bfrB gene, and (ii) perturbing the BfrB:Bfd interaction in P. aeruginosa cells by either deleting the bfd gene or by replacing the wild type bfrB gene with a L68A/E81A double mutant allele in the P. aeruginosa chromosome. The effects of the mutations were evaluated by following the accumulation of iron in BfrB, analyzing levels of free and total intracellular iron, and by characterizing the ensuing iron homeostasis dysregulation phenotypes. The results reveal that P. aeruginosa accumulates iron mainly in BfrB, and that the nutrient does not accumulate in FtnA to detectable levels, even after deletion of the bfrB gene. Perturbing the BfrB:Bfd interaction causes irreversible flow of iron into BfrB, which leads to the accumulation of unusable intracellular iron while severely depleting the levels of free intracellular iron, which drives the cells to an acute iron starvation response despite harboring "normal" levels of total intracellular iron. These results are discussed in the context of a dynamic equilibrium between free cytosolic Fe2+ and Fe3+ compartmentalized in BfrB, which functions as a buffer to oppose rapid changes of free cytosolic iron. Finally, we also show that P. aeruginosa cells utilize iron stored in BfrB for growth in iron-limiting conditions, and that the utilization of BfrB-iron requires a functional BfrB:Bfd interaction.
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Affiliation(s)
- Kate Eshelman
- Department of Chemistry and R. N. Adams Institute for Bioanalytical Chemistry, University of Kansas, Multidisciplinary Research Building, 2030 Becker Dr, Lawrence, KS 66047, USA.
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23
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Zhang X, Lu C, Zhang F, Song Y, Cai M, Zhu H. Streptococcal heme binding protein (Shp) promotes virulence and contributes to the pathogenesis of group A Streptococcus infection. Pathog Dis 2018; 75:4002673. [PMID: 28830075 DOI: 10.1093/femspd/ftx085] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Accepted: 07/20/2017] [Indexed: 01/28/2023] Open
Abstract
Streptococcal heme binding protein (Shp) is involved in the process of heme acquisition in group A Streptococcus (GAS). However, no research thus far has examined the contribution of Shp to the virulence of GAS. To this end, we generated an isogenic strain lacking the shp gene (Δshp) and its complemented strain (Δshp-c) using the parent strain MGAS5005 (WT). Deletion of shp increased survival rates and neutrophil recruitment and reduced skin lesion sizes and GAS loads in the blood and the liver, lung, kidney and spleen in subcutaneous infections of mice. These results indicate that Shp significantly contributes to the skin and systemic invasion of GAS. The growth of the Δshp mutant was significantly slower than MGAS5005 and Δshp-c than in non-immune human blood and in incubation with isolated rat neutrophils. Microarray transcriptional analyses found no alteration in expression of virulence genes, indicating that the phenotype of the Δshp mutant was directly linked to the lack of Shp. The findings indicate that Shp significantly contributes to GAS skin invasion, systemic infection and virulence and that these contributions of Shp are mediated by the effects of Shp on systemic GAS growth and neutrophil responses.
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Affiliation(s)
- Xiaolan Zhang
- College of Basic Medical Sciences, Harbin Medical University, 150086 Harbin, China
| | - Chunmei Lu
- College of Basic Medical Sciences, Harbin Medical University, 150086 Harbin, China
| | - Fengmin Zhang
- College of Basic Medical Sciences, Harbin Medical University, 150086 Harbin, China
| | - Yingli Song
- College of Basic Medical Sciences, Harbin Medical University, 150086 Harbin, China
| | - Minghui Cai
- College of Basic Medical Sciences, Harbin Medical University, 150086 Harbin, China
| | - Hui Zhu
- College of Basic Medical Sciences, Harbin Medical University, 150086 Harbin, China
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24
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Conger MA, Pokhrel D, Liptak MD. Tight binding of heme to Staphylococcus aureus IsdG and IsdI precludes design of a competitive inhibitor. Metallomics 2018; 9:556-563. [PMID: 28401968 DOI: 10.1039/c7mt00035a] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The micromolar equilibrium constants for heme dissociation from IsdG and IsdI reported in the literature call into question whether these enzymes are actually members of the iron-regulated surface determinant system of Staphylococcus aureus, which harvests heme iron from a host during infection. In order to address this question, the heme dissociation constants for IsdG and IsdI were reevaluated using three approaches. The heme dissociation equilibrium constants were measured using a UV/Vis absorption-detected assay analyzed with an assumption-free model, and using a newly developed fluorescence-detected assay. The heme dissociation rate constants were estimated using apomyoglobin competition assays. Analyses of the UV/Vis absorption data revealed a critical flaw in the previous measurements; heme is 99.9% protein-bound at the micromolar concentrations needed for UV/Vis absorption spectroscopy, which renders accurate equilibrium constant measurement nearly impossible. However, fluorescence can be measured for more dilute samples, and analyses of these data resulted in dissociation equilibrium constants of 1.4 ± 0.6 nM and 12.9 ± 1.3 nM for IsdG and IsdI, respectively. Analyses of the kinetic data obtained from apomyoglobin competition assays estimated heme dissociation rate constants of 0.022 ± 0.002 s-1 for IsdG and 0.092 ± 0.008 s-1 for IsdI. Based upon these data, and what is known regarding the post-translational regulation of IsdG and IsdI, it is proposed that only IsdG is a member of the heme iron acquisition pathway and IsdI regulates heme homeostasis. Furthermore, the nanomolar dissociation constants mean that heme is bound tightly by IsdG and indicates that competitive inhibition of this protein will be difficult. Instead, uncompetitive inhibition based upon a detailed understanding of enzyme mechanism is a more promising antibiotic development strategy.
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Affiliation(s)
- Matthew A Conger
- Department of Chemistry, University of Vermont, Burlington, Vermont 05405, USA.
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25
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Kawano H, Miyamoto K, Yasunobe M, Murata M, Yamahata E, Yamaguchi R, Miyaki Y, Tsuchiya T, Tanabe T, Funahashi T, Tsujibo H. Identification of the heme acquisition system in Vibrio vulnificus M2799. Microb Pathog 2018; 117:100-108. [PMID: 29432914 DOI: 10.1016/j.micpath.2018.02.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 02/09/2018] [Accepted: 02/09/2018] [Indexed: 01/16/2023]
Abstract
Vibrio vulnificus, the causative agent of serious, often fatal, infections in humans, requires iron for its pathogenesis. As such, it obtains iron via both vulnibactin and heme-mediated iron-uptake systems. In this study, we identified the heme acquisition system in V. vulnificus M2799. The nucleotide sequences of the genes encoding heme receptors HupA and HvtA and the ATP-binding cassette (ABC) transport system proteins HupB, HupC, and HupD were determined, and then used in the construction of deletion mutants developed from a Δics strain, which could not synthesize vulnibactin. Growth experiments using these mutants indicated that HupA and HvtA are major and minor heme receptors, respectively. The expressions of two proteins were analyzed by the quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR). Furthermore, complementation analyses confirmed that the HupBCD proteins are the only ABC transport system shared by both the HupA and HvtA receptors. This is the first genetic evidence that the HupBCD proteins are essential for heme acquisition by V. vulnificus. Further investigation showed that hupA, hvtA, and hupBCD are regulated by Fur. The qRT-PCR analysis of the heme receptor genes revealed that HupR, a LysR-family positive transcriptional activator, upregulates the expression of hupA, but not hvtA. In addition, ptrB was co-transcribed with hvtA, and PtrB had no influence on growth in low-iron CM9 medium supplemented with hemin, hemoglobin, or cytochrome C.
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Affiliation(s)
- Hiroaki Kawano
- Department of Microbiology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan
| | - Katsushiro Miyamoto
- Department of Microbiology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan
| | - Megumi Yasunobe
- Department of Microbiology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan
| | - Masahiro Murata
- Department of Microbiology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan
| | - Eri Yamahata
- Department of Microbiology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan
| | - Ryo Yamaguchi
- Department of Microbiology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan
| | - Yuta Miyaki
- Department of Microbiology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan
| | - Takahiro Tsuchiya
- Department of Microbiology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan
| | - Tomotaka Tanabe
- Laboratory of Hygienic Chemistry, College of Pharmaceutical Sciences, Matsuyama University, 4-2 Bunkyo-cho, Matsuyama, Ehime 790-8578, Japan
| | - Tatsuya Funahashi
- Laboratory of Hygienic Chemistry, College of Pharmaceutical Sciences, Matsuyama University, 4-2 Bunkyo-cho, Matsuyama, Ehime 790-8578, Japan
| | - Hiroshi Tsujibo
- Department of Microbiology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan.
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26
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Lin TH, Tseng CY, Lai YC, Wu CC, Huang CF, Lin CT. IscR Regulation of Type 3 Fimbriae Expression in Klebsiella pneumoniae CG43. Front Microbiol 2017; 8:1984. [PMID: 29085346 PMCID: PMC5650617 DOI: 10.3389/fmicb.2017.01984] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 09/26/2017] [Indexed: 01/25/2023] Open
Abstract
In Klebsiella pneumoniae, we have previously shown that IscR, an Fe–S cluster-containing transcriptional factor, plays a dual role in controlling capsular polysaccharide biosynthesis and iron-acquisition systems by switching between its holo and apo forms. In this study, the effect of IscR on type 3 fimbriae expression and biofilm formation was investigated. We found that production of the major subunit of type 3 fimbriae, MrkA, was increased in the ΔiscR and iscR3CA strains, a strain expressing a mutant IscR that mimics apo-IscR, at both the translational and transcriptional levels. Based on the fact that type 3 fimbriae expression is the major factor affecting biofilm formation, increased biofilm formation was also found in ΔiscR or iscR3CA, suggesting that holo-IscR represses biofilm formation. However, the repression of type 3 fimbriae expression by IscR is indirect. To further understand the regulatory mechanism of IscR, the effect of IscR on the expression of mrkHIJ, which encodes cyclic di-GMP (c-di-GMP)-related regulatory proteins that control type 3 fimbriae expression, was studied. We found that holo-IscR could directly repress mrkHI transcription, indicating that MrkHI is required for IscR regulation of type 3 fimbriae expression. Finally, deletion of iscR attenuated K. pneumoniae virulence in a peritonitis model of mouse infection, while the absence of the [2Fe–2S] cluster of IscR had no effect on K. pneumoniae virulence during infection. Taken together, our results demonstrate the underlying mechanism of the [2Fe–2S] cluster of IscR in controlling type 3 fimbriae expression and its effect on K. pneumoniae pathogenesis.
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Affiliation(s)
- Tien-Huang Lin
- Division of Urology, Taichung Tzu Chi General Hospital, The Buddhist Tzu Chi Medical Foundation, Taichung, Taiwan.,School of Post-Baccalaureate Chinese Medicine, Tzu Chi University, Hualien, Taiwan
| | - Cheng-Yin Tseng
- Graduate Institute of Chinese Medicine, China Medical University, Taichung, Taiwan.,Section of Infectious Disease, Hsinchu Mackay Memorial Hospital, Hsinchu, Taiwan
| | - Yi-Chyi Lai
- Department of Microbiology and Immunology, Chung-Shan Medical University, Taichung, Taiwan
| | - Chien-Chen Wu
- School of Chinese Medicine, China Medical University, Taichung, Taiwan
| | - Chun-Fa Huang
- Graduate Institute of Chinese Medicine, China Medical University, Taichung, Taiwan.,School of Chinese Medicine, China Medical University, Taichung, Taiwan
| | - Ching-Ting Lin
- Graduate Institute of Chinese Medicine, China Medical University, Taichung, Taiwan.,School of Chinese Medicine, China Medical University, Taichung, Taiwan
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27
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Constante M, Fragoso G, Calvé A, Samba-Mondonga M, Santos MM. Dietary Heme Induces Gut Dysbiosis, Aggravates Colitis, and Potentiates the Development of Adenomas in Mice. Front Microbiol 2017; 8:1809. [PMID: 28983289 PMCID: PMC5613120 DOI: 10.3389/fmicb.2017.01809] [Citation(s) in RCA: 87] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Accepted: 09/05/2017] [Indexed: 12/15/2022] Open
Abstract
Dietary heme can be used by colonic bacteria equipped with heme-uptake systems as a growth factor and thereby impact on the microbial community structure. The impact of heme on the gut microbiota composition may be particularly pertinent in chronic inflammation such as in inflammatory bowel disease (IBD), where a strong association with gut dysbiosis has been consistently reported. In this study we investigated the influence of dietary heme on the gut microbiota and inferred metagenomic composition, and on chemically induced colitis and colitis-associated adenoma development in mice. Using 16S rRNA gene sequencing, we found that mice fed a diet supplemented with heme significantly altered their microbiota composition, characterized by a decrease in α-diversity, a reduction of Firmicutes and an increase of Proteobacteria, particularly Enterobacteriaceae. These changes were similar to shifts seen in dextran sodium sulfate (DSS)-treated mice to induce colitis. In addition, dietary heme, but not systemically delivered heme, contributed to the exacerbation of DSS-induced colitis and facilitated adenoma formation in the azoxymethane/DSS colorectal cancer (CRC) mouse model. Using inferred metagenomics, we found that the microbiota alterations elicited by dietary heme resulted in non-beneficial functional shifts, which were also characteristic of DSS-induced colitis. Furthermore, a reduction in fecal butyrate levels was found in mice fed the heme supplemented diet compared to mice fed the control diet. Iron metabolism genes known to contribute to heme release from red blood cells, heme uptake, and heme exporter proteins, were significantly enriched, indicating a shift toward favoring the growth of bacteria able to uptake heme and protect against its toxicity. In conclusion, our data suggest that luminal heme, originating from dietary components or gastrointestinal bleeding in IBD and, to lesser extent in CRC, directly contributes to microbiota dysbiosis. Thus, luminal heme levels may further exacerbate colitis through the modulation of the gut microbiota and its metagenomic functional composition. Our data may have implications in the development of novel targets for therapeutic approaches aimed at lowering gastrointestinal heme levels through heme chelation or degradation using probiotics and nutritional interventions.
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Affiliation(s)
- Marco Constante
- Département de Médecine, Université de Montréal, MontréalQC, Canada.,Nutrition and Microbiome Laboratory, Institut du Cancer de Montréal, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, MontréalQC, Canada
| | - Gabriela Fragoso
- Nutrition and Microbiome Laboratory, Institut du Cancer de Montréal, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, MontréalQC, Canada
| | - Annie Calvé
- Nutrition and Microbiome Laboratory, Institut du Cancer de Montréal, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, MontréalQC, Canada
| | - Macha Samba-Mondonga
- Nutrition and Microbiome Laboratory, Institut du Cancer de Montréal, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, MontréalQC, Canada
| | - Manuela M Santos
- Département de Médecine, Université de Montréal, MontréalQC, Canada.,Nutrition and Microbiome Laboratory, Institut du Cancer de Montréal, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, MontréalQC, Canada
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28
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Tanner R, O’Shea MK, White AD, Müller J, Harrington-Kandt R, Matsumiya M, Dennis MJ, Parizotto EA, Harris S, Stylianou E, Naranbhai V, Bettencourt P, Drakesmith H, Sharpe S, Fletcher HA, McShane H. The influence of haemoglobin and iron on in vitro mycobacterial growth inhibition assays. Sci Rep 2017; 7:43478. [PMID: 28256545 PMCID: PMC5335253 DOI: 10.1038/srep43478] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 01/24/2017] [Indexed: 01/04/2023] Open
Abstract
The current vaccine against tuberculosis, live attenuated Mycobacterium bovis BCG, has variable efficacy, but development of an effective alternative is severely hampered by the lack of an immune correlate of protection. There has been a recent resurgence of interest in functional in vitro mycobacterial growth inhibition assays (MGIAs), which provide a measure of a range of different immune mechanisms and their interactions. We identified a positive correlation between mean corpuscular haemoglobin and in vitro growth of BCG in whole blood from healthy UK human volunteers. Mycobacterial growth in peripheral blood mononuclear cells (PBMC) from both humans and macaques was increased following the experimental addition of haemoglobin (Hb) or ferric iron, and reduced following addition of the iron chelator deferoxamine (DFO). Expression of Hb genes correlated positively with mycobacterial growth in whole blood from UK/Asian adults and, to a lesser extent, in PBMC from South African infants. Taken together our data indicate an association between Hb/iron levels and BCG growth in vitro, which may in part explain differences in findings between whole blood and PBMC MGIAs and should be considered when using such assays.
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Affiliation(s)
- Rachel Tanner
- The Jenner Institute, University of Oxford, Oxford, UK
| | | | | | - Julius Müller
- The Jenner Institute, University of Oxford, Oxford, UK
| | | | | | | | | | | | | | | | | | - Hal Drakesmith
- Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
| | - Sally Sharpe
- Public Health England, Porton Down, Salisbury, UK
| | | | - Helen McShane
- The Jenner Institute, University of Oxford, Oxford, UK
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29
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Abstract
Iron is essential for replication of Mycobacterium tuberculosis, but iron is efficiently sequestered in the human host during infection. Heme constitutes the largest iron reservoir in the human body and is utilized by many bacterial pathogens as an iron source. While heme acquisition is well studied in other bacterial pathogens, little is known in M. tuberculosis. To identify proteins involved in heme utilization by M. tuberculosis, a transposon mutant library was screened for resistance to the toxic heme analog gallium(III)-porphyrin (Ga-PIX). Inactivation of the ppe36, ppe62, and rv0265c genes resulted in resistance to Ga-PIX. Growth experiments using isogenic M. tuberculosis deletion mutants showed that PPE36 is essential for heme utilization by M. tuberculosis, while the functions of PPE62 and Rv0265c are partially redundant. None of the genes restored growth of the heterologous M. tuberculosis mutants, indicating that the proteins encoded by the genes have separate functions. PPE36, PPE62, and Rv0265c bind heme as shown by surface plasmon resonance spectroscopy and are associated with membranes. Both PPE36 and PPE62 proteins are cell surface accessible, while the Rv0265c protein is probably located in the periplasm. PPE36 and PPE62 are, to our knowledge, the first proline-proline-glutamate (PPE) proteins of M. tuberculosis that bind small molecules and are involved in nutrient acquisition. The absence of a virulence defect of the ppe36 deletion mutant indicates that the different iron acquisition pathways of M. tuberculosis may substitute for each other during growth and persistence in mice. The emerging model of heme utilization by M. tuberculosis as derived from this study is substantially different from those of other bacteria. Tuberculosis is caused by Mycobacterium tuberculosis and is a devastating disease affecting eight million people each year. Iron is an essential nutrient for replication of M. tuberculosis in the human host. More than 70% of iron in the human body is bound in heme. Not surprisingly, many bacterial pathogens, including M. tuberculosis, are able to acquire iron from heme. However, the mechanism of heme uptake by M. tuberculosis is poorly understood. We have identified two novel surface proteins that bind heme and are required for heme utilization by M. tuberculosis. These findings constitute a major advancement of our understanding of iron acquisition by M. tuberculosis and show that M. tuberculosis has evolved heme uptake systems different from the paradigms established by other bacteria.
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30
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Kim H, Chaurasia AK, Kim T, Choi J, Ha SC, Kim D, Kim KK. Structural and functional study of ChuY from Escherichia coli strain CFT073. Biochem Biophys Res Commun 2016; 482:1176-1182. [PMID: 27919686 DOI: 10.1016/j.bbrc.2016.12.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2016] [Accepted: 12/02/2016] [Indexed: 10/20/2022]
Abstract
The uropathogenic Escherichia coli strain CFT073 contains multiple iron and heme transport systems, which facilitate infection of the host urinary tract. To elucidate the molecular and cellular function of ChuY, a hypothetical gene in the heme degradation/utilization pathway, we solved the crystal structure of ChuY at 2.4 Å resolution. ChuY has high structural homology with human biliverdin and flavin reductase. We confirmed that ChuY has flavin mononucleotide (FMN) reductase activity, using NAD(P)H as a cofactor, and shows porphyrin ring binding affinity. A chuY deletion-insertion strain showed reduced survival potential compared to wild-type and complemented strains in mammalian cells. Current results suggest ChuY acts as a reductase in heme homeostasis to maintain the virulence potential of E. coli CFT073.
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Affiliation(s)
- Hun Kim
- Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Suwon, Gyeonggi 16419, South Korea
| | - Akhilesh Kumar Chaurasia
- Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Suwon, Gyeonggi 16419, South Korea
| | - Truc Kim
- Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Suwon, Gyeonggi 16419, South Korea
| | - Jongkeun Choi
- Department of Cosmetic Science, Chungwoon University, Hongseong, Chungnam 32244, South Korea
| | - Sung Chul Ha
- Pohang Accelerator Laboratory, Pohang, Gyeongbuk 37673, South Korea
| | - Doyoun Kim
- Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Suwon, Gyeonggi 16419, South Korea
| | - Kyeong Kyu Kim
- Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Suwon, Gyeonggi 16419, South Korea.
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31
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Amolegbe SA, Akinremi CA, Adewuyi S, Lawal A, Bamigboye MO, Obaleye JA. Some nontoxic metal-based drugs for selected prevalent tropical pathogenic diseases. J Biol Inorg Chem 2016; 22:1-18. [DOI: 10.1007/s00775-016-1421-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2016] [Accepted: 11/18/2016] [Indexed: 02/04/2023]
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32
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Radical new paradigm for heme degradation in Escherichia coli O157:H7. Proc Natl Acad Sci U S A 2016; 113:12138-12143. [PMID: 27791000 DOI: 10.1073/pnas.1603209113] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
All of the heme-degrading enzymes that have been characterized to date require molecular oxygen as a cosubstrate. Escherichia coli O157:H7 has been shown to express heme uptake and transport proteins, as well as use heme as an iron source. This enteric pathogen colonizes the anaerobic space of the lower intestine in mammals, yet no mechanism for anaerobic heme degradation has been reported. Herein we provide evidence for an oxygen-independent heme-degradation pathway. Specifically, we demonstrate that ChuW is a radical S-adenosylmethionine methyltransferase that catalyzes a radical-mediated mechanism facilitating iron liberation and the production of the tetrapyrrole product we termed "anaerobilin." We further demonstrate that anaerobilin can be used as a substrate by ChuY, an enzyme that is coexpressed with ChuW in vivo along with the heme uptake machinery. Our findings are discussed in terms of the competitive advantage this system provides for enteric bacteria, particularly those that inhabit an anaerobic niche in the intestines.
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33
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Sigala PA, Morante K, Tsumoto K, Caaveiro JMM, Goldberg DE. In-Cell Enzymology To Probe His-Heme Ligation in Heme Oxygenase Catalysis. Biochemistry 2016; 55:4836-49. [PMID: 27490825 DOI: 10.1021/acs.biochem.6b00562] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Heme oxygenase (HO) is a ubiquitous enzyme with key roles in inflammation, cell signaling, heme disposal, and iron acquisition. HO catalyzes the oxidative conversion of heme to biliverdin (BV) using a conserved histidine to coordinate the iron atom of bound heme. This His-heme interaction has been regarded as being essential for enzyme activity, because His-to-Ala mutants fail to convert heme to biliverdin in vitro. We probed a panel of proximal His mutants of cyanobacterial, human, and plant HO enzymes using a live-cell activity assay based on heterologous co-expression in Escherichia coli of each HO mutant and a fluorescent biliverdin biosensor. In contrast to in vitro studies with purified proteins, we observed that multiple HO mutants retained significant activity within the intracellular environment of bacteria. X-ray crystallographic structures of human HO1 H25R with bound heme and additional functional studies suggest that HO mutant activity inside these cells does not involve heme ligation by a proximal amino acid. Our study reveals unexpected plasticity in the active site binding interactions with heme that can support HO activity within cells, suggests important contributions by the surrounding active site environment to HO catalysis, and can guide efforts to understand the evolution and divergence of HO function.
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Affiliation(s)
- Paul A Sigala
- Departments of Medicine and Molecular Microbiology, Washington University School of Medicine , St. Louis, Missouri 63110, United States
| | - Koldo Morante
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo , Bunkyo-ku, Tokyo 113-8654, Japan
| | - Kouhei Tsumoto
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo , Bunkyo-ku, Tokyo 113-8654, Japan.,Medical Proteomics Laboratory, Institute of Medical Science, The University of Tokyo , Minato-ku, Tokyo 108-8639, Japan
| | - Jose M M Caaveiro
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo , Bunkyo-ku, Tokyo 113-8654, Japan
| | - Daniel E Goldberg
- Departments of Medicine and Molecular Microbiology, Washington University School of Medicine , St. Louis, Missouri 63110, United States
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34
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Mouriño S, Giardina BJ, Reyes-Caballero H, Wilks A. Metabolite-driven Regulation of Heme Uptake by the Biliverdin IXβ/δ-Selective Heme Oxygenase (HemO) of Pseudomonas aeruginosa. J Biol Chem 2016; 291:20503-15. [PMID: 27493207 DOI: 10.1074/jbc.m116.728527] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Indexed: 11/06/2022] Open
Abstract
Pseudomonas aeruginosa acquires extracellular heme via the Phu (Pseudomonas heme uptake) and Has (heme assimilation system) systems. We have previously shown the catalytic actions of heme oxygenase (HemO) along with the cytoplasmic heme transport protein PhuS control heme flux into the cell. To further investigate the role of the PhuS-HemO couple in modulating heme uptake, we have characterized two HemO variants, one that is catalytically inactive (HemO H26A/K34A/K132A or HemOin) and one that has altered regioselectivity (HemO N19K/K34A/F117Y/K132A or HemOα), producing biliverdin IXα (BVIXα). HemOα similar to wild type was able to interact and acquire heme from holo-PhuS. In contrast, the HemOin variant did not interact with holo-PhuS and showed no enzymatic activity. Complementation of a hemO deletion strain with the hemOin or hemOα variants in combination with [(13)C]heme isotopic labeling experiments revealed that the absence of BVIXβ and BVIXδ leads to a decrease in extracellular levels of hemophore HasA. We propose BVIXβ and/or BVIXδ transcriptionally or post-transcriptionally regulates HasA. Thus, coupling the PhuS-dependent flux of heme through HemO to feedback regulation of the cell surface signaling system through HasA allows P. aeruginosa to rapidly respond to fluctuating extracellular heme levels independent of the iron status of the cell.
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Affiliation(s)
- Susana Mouriño
- From the Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201
| | - Bennett J Giardina
- From the Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201
| | - Hermes Reyes-Caballero
- From the Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201
| | - Angela Wilks
- From the Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201
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35
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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.
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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.
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36
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Intraspecies Transfer of the Chromosomal Acinetobacter baumannii blaNDM-1 Carbapenemase Gene. Antimicrob Agents Chemother 2016; 60:3032-40. [PMID: 26953198 DOI: 10.1128/aac.00124-16] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 03/02/2016] [Indexed: 11/20/2022] Open
Abstract
The species Acinetobacter baumannii is one of the most important multidrug-resistant human pathogens. To determine its virulence and antibiotic resistance determinants, the genome of the nosocomial blaNDM-1-positive A. baumannii strain R2090 originating from Egypt was completely sequenced. Genome analysis revealed that strain R2090 is highly related to the community-acquired Australian A. baumannii strain D1279779. The two strains belong to sequence type 267 (ST267). Isolate R2090 harbored the chromosomally integrated transposon Tn125 carrying the carbapenemase gene blaNDM-1 that is not present in the D1279779 genome. To test the transferability of the metallo-β-lactamase (MBL) gene region, the clinical isolate R2090 was mated with the susceptible A. baumannii recipient CIP 70.10, and the carbapenem-resistant derivative R2091 was obtained. Genome sequencing of the R2091 derivative revealed that it had received an approximately 66-kb region comprising the transposon Tn125 embedding the blaNDM-1 gene. This region had integrated into the chromosome of the recipient strain CIP 70.10. From the four known mechanisms for horizontal gene transfer (conjugation, outer membrane vesicle-mediated transfer, transformation, and transduction), conjugation could be ruled out, since strain R2090 lacks any plasmid, and a type IV secretion system is not encoded in its chromosome. However, strain R2090 possesses three putative prophages, two of which were predicted to be complete and therefore functional. Accordingly, it was supposed that the transfer of the resistance gene region from the clinical isolate R2090 to the recipient occurred by general transduction facilitated by one of the prophages present in the R2090 genome. Hence, phage-mediated transduction has to be taken into account for the dissemination of antibiotic resistance genes within the species A. baumannii.
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Unique coupling of mono- and dioxygenase chemistries in a single active site promotes heme degradation. Proc Natl Acad Sci U S A 2016; 113:3779-84. [PMID: 27006503 DOI: 10.1073/pnas.1523333113] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bacterial pathogens must acquire host iron for survival and colonization. Because free iron is restricted in the host, numerous pathogens have evolved to overcome this limitation by using a family of monooxygenases that mediate the oxidative cleavage of heme into biliverdin, carbon monoxide, and iron. However, the etiological agent of tuberculosis, Mycobacterium tuberculosis, accomplishes this task without generating carbon monoxide, which potentially induces its latent state. Here we show that this unusual heme degradation reaction proceeds through sequential mono- and dioxygenation events within the single active center of MhuD, a mechanism unparalleled in enzyme catalysis. A key intermediate of the MhuD reaction is found to be meso-hydroxyheme, which reacts with O2 at an unusual position to completely suppress its monooxygenation but to allow ring cleavage through dioxygenation. This mechanistic change, possibly due to heavy steric deformation of hydroxyheme, rationally explains the unique heme catabolites of MhuD. Coexistence of mechanistically distinct functions is a previously unidentified strategy to expand the physiological outcome of enzymes, and may be applied to engineer unique biocatalysts.
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Sekine Y, Tanzawa T, Tanaka Y, Ishimori K, Uchida T. Cytoplasmic Heme-Binding Protein (HutX) from Vibrio cholerae Is an Intracellular Heme Transport Protein for the Heme-Degrading Enzyme, HutZ. Biochemistry 2016; 55:884-93. [DOI: 10.1021/acs.biochem.5b01273] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yukari Sekine
- Graduate
School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-0810, Japan
| | - Takehito Tanzawa
- Graduate
School of Life Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Yoshikazu Tanaka
- Faculty
of Advanced Life Science, Hokkaido University, Sapporo 060-0810, Japan
- PRESTO, Japan Science and Technology Agency, Sapporo 060-0810, Japan
| | - Koichiro Ishimori
- Graduate
School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-0810, Japan
- Department
of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Takeshi Uchida
- Graduate
School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-0810, Japan
- Department
of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan
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The Trypanosoma cruzi Protein TcHTE Is Critical for Heme Uptake. PLoS Negl Trop Dis 2016; 10:e0004359. [PMID: 26752206 PMCID: PMC4713871 DOI: 10.1371/journal.pntd.0004359] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 12/14/2015] [Indexed: 01/08/2023] Open
Abstract
Trypanosoma cruzi, the etiological agent of Chagas' disease, presents nutritional requirements for several metabolites. It requires heme for the biosynthesis of several heme-proteins involved in essential metabolic pathways like mitochondrial cytochromes and respiratory complexes, as well as enzymes involved in the biosynthesis of sterols and unsaturated fatty acids. However, this parasite lacks a complete route for its synthesis. In view of these facts, T. cruzi has to incorporate heme from the environment during its life cycle. In other words, their hosts must supply the heme for heme-protein synthesis. Although the acquisition of heme is a fundamental issue for the parasite's replication and survival, how this cofactor is imported and distributed is poorly understood. In this work, we used different fluorescent heme analogs to explore heme uptake along the different life-cycle stages of T. cruzi, showing that this parasite imports it during its replicative stages: the epimastigote in the insect vector and the intracellular amastigote in the mammalian host. Also, we identified and characterized a T. cruzi protein (TcHTE) with 55% of sequence similarity to LHR1 (protein involved in L. amazonensis heme transport), which is located in the flagellar pocket, where the transport of nutrients proceeds in trypanosomatids. We postulate TcHTE as a protein involved in improving the efficiency of the heme uptake or trafficking in T. cruzi.
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Renberg RL, Yuan X, Samuel TK, Miguel DC, Hamza I, Andrews NW, Flannery AR. The Heme Transport Capacity of LHR1 Determines the Extent of Virulence in Leishmania amazonensis. PLoS Negl Trop Dis 2015; 9:e0003804. [PMID: 26001191 PMCID: PMC4441390 DOI: 10.1371/journal.pntd.0003804] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 05/01/2015] [Indexed: 12/14/2022] Open
Abstract
Leishmania spp. are trypanosomatid parasites that replicate intracellularly in macrophages, causing serious human morbidity and mortality throughout the world. Trypanosomatid protozoa cannot synthesize heme, so must acquire this essential cofactor from their environment. Earlier studies identified LHR1 as a Leishmania amazonensis transmembrane protein that mediates heme uptake. Null mutants of LHR1 are not viable and single knockout strains have reduced virulence, but very little is known about the properties of LHR1 directly associated with heme transport. Here, we use functional assays in Saccharomyces cerevisiae to show that specific tyrosine residues within the first three predicted transmembrane domains of LHR1 are required for efficient heme uptake. These tyrosines are unique to LHR1, consistent with the low similarity between LHR1 and its corresponding homologs in C. elegans and human. Substitution of these tyrosines in LHR1 resulted in varying degrees of heme transport inhibition, phenotypes that closely mirrored the impaired ability of L. amazonensis to replicate as intracellular amastigotes in macrophages and generate cutaneous lesions in mice. Taken together, our results imply that the mechanism for heme transport by LHR1 is distinctive and may have adapted to secure heme, a limiting cofactor, inside the host. Since LHR1 is significantly divergent from the human heme transporter HRG1, our findings lay the groundwork for selective targeting of LHR1 by small molecule antagonists. Leishmania are protozoan parasites that infect humans and replicate intracellularly in macrophages, cells normally engaged in protecting the host from pathogens. These parasites have several strategies to survive inside the hostile environment of the host macrophage, and one of these strategies involves heme acquisition. Heme is an iron-containing molecule that is essential for many cellular functions. Unlike mammalian cells, Leishmania parasites cannot synthesize heme, so must acquire it from the host cell. In earlier work we found that the parasites express a surface protein, LHR1, which transports heme into the parasites. In this study we identified specific amino acids in LHR1 that are required for heme transport. When expressed in yeast cells, LHR1 carrying these mutations had defects in heme transport that were equivalent to the inhibition in virulence observed when these proteins were expressed in Leishmania and tested in macrophage and mouse infection assays. These critical amino acids do not exist in the human heme transporter, indicating that LHR1 is a promising target for the development of specific drugs for the treatment of leishmaniasis and possibly other serious parasitic diseases, such as Chagas’ disease and sleeping sickness.
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Affiliation(s)
- Rebecca L. Renberg
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, United States of America
| | - Xiaojing Yuan
- Department of Animal and Avian Sciences, University of Maryland, College Park, Maryland, United States of America
| | - Tamika K. Samuel
- Department of Animal and Avian Sciences, University of Maryland, College Park, Maryland, United States of America
| | - Danilo C. Miguel
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, United States of America
| | - Iqbal Hamza
- Department of Animal and Avian Sciences, University of Maryland, College Park, Maryland, United States of America
| | - Norma W. Andrews
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, United States of America
- * E-mail: ,
| | - Andrew R. Flannery
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, United States of America
- PathSensors, Inc., Baltimore, Maryland, United States of America
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Identification of in vivo-induced bacterial protein antigens during calf infection with Chlamydia psittaci. Int J Med Microbiol 2015; 305:310-21. [DOI: 10.1016/j.ijmm.2014.12.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2014] [Revised: 11/19/2014] [Accepted: 12/20/2014] [Indexed: 01/21/2023] Open
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Smith AD, Modi AR, Sun S, Dawson JH, Wilks A. Spectroscopic Determination of Distinct Heme Ligands in Outer-Membrane Receptors PhuR and HasR of Pseudomonas aeruginosa. Biochemistry 2015; 54:2601-12. [PMID: 25849630 DOI: 10.1021/acs.biochem.5b00017] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Pseudomonas aeruginosa PAO1 encodes two outer membrane receptors, PhuR (Pseudomonas heme uptake) and HasR (heme assimilation system). The HasR receptor acquires heme through interaction with a secreted hemophore, HasAp. The non-hemophore-dependent PhuR is encoded along with proteins required for heme translocation into the cytoplasm. Herein, we report the isolation and characterization of the HasR and PhuR receptors. Absorption and MCD spectroscopy confirmed that, similar to other Gram-negative OM receptors, HasR coordinates heme through the conserved N-terminal plug His-221 and His-624 of the surface-exposed FRAP-loop. In contrast, PhuR showed distinct absorption and MCD spectra consistent with coordination through a Tyr residue. Sequence alignment of PhuR with all known Gram-negative OM heme receptors revealed a lack of a conserved His within the FRAP loop but two Tyr residues at positions 519 and 529. Site-directed mutagenesis and spectroscopic characterization confirmed Tyr-519 and the N-terminal plug His-124 provide the heme ligands in PhuR. We propose that PhuR and HasR represent nonredundant heme receptors capable of sensing and accessing heme across a wide range of physiological conditions on colonization and infection of the host.
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Affiliation(s)
- Aaron D Smith
- †Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201, United States
| | - Anuja R Modi
- ‡Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Shengfang Sun
- ‡Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - John H Dawson
- ‡Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Angela Wilks
- †Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201, United States
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Ou HY, Kuang SN, He X, Molgora BM, Ewing PJ, Deng Z, Osby M, Chen W, Xu HH. Complete genome sequence of hypervirulent and outbreak-associated Acinetobacter baumannii strain LAC-4: epidemiology, resistance genetic determinants and potential virulence factors. Sci Rep 2015; 5:8643. [PMID: 25728466 PMCID: PMC4345345 DOI: 10.1038/srep08643] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 01/29/2015] [Indexed: 12/22/2022] Open
Abstract
Acinetobacter baumannii is an important human pathogen due to its multi-drug resistance. In this study, the genome of an ST10 outbreak A. baumannii isolate LAC-4 was completely sequenced to better understand its epidemiology, antibiotic resistance genetic determinants and potential virulence factors. Compared with 20 other complete genomes of A. baumannii, LAC-4 genome harbors at least 12 copies of five distinct insertion sequences. It contains 12 and 14 copies of two novel IS elements, ISAba25 and ISAba26, respectively. Additionally, three novel composite transposons were identified: Tn6250, Tn6251 and Tn6252, two of which contain resistance genes. The antibiotic resistance genetic determinants on the LAC-4 genome correlate well with observed antimicrobial susceptibility patterns. Moreover, twelve genomic islands (GI) were identified in LAC-4 genome. Among them, the 33.4-kb GI12 contains a large number of genes which constitute the K (capsule) locus. LAC-4 harbors several unique putative virulence factor loci. Furthermore, LAC-4 and all 19 other outbreak isolates were found to harbor a heme oxygenase gene (hemO)-containing gene cluster. The sequencing of the first complete genome of an ST10 A. baumannii clinical strain should accelerate our understanding of the epidemiology, mechanisms of resistance and virulence of A. baumannii.
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Affiliation(s)
- Hong-Yu Ou
- State Key Laboratory of Microbial Metabolism and School of Life Sciences &Biotechnology, Shanghai Jiaotong University, Shanghai, China
| | - Shan N Kuang
- Department of Biological Sciences, California State University Los Angeles, Los Angeles, California, USA
| | - Xinyi He
- State Key Laboratory of Microbial Metabolism and School of Life Sciences &Biotechnology, Shanghai Jiaotong University, Shanghai, China
| | - Brenda M Molgora
- Department of Biological Sciences, California State University Los Angeles, Los Angeles, California, USA
| | - Peter J Ewing
- Department of Biological Sciences, California State University Los Angeles, Los Angeles, California, USA
| | - Zixin Deng
- State Key Laboratory of Microbial Metabolism and School of Life Sciences &Biotechnology, Shanghai Jiaotong University, Shanghai, China
| | - Melanie Osby
- Department of Pathology, LAC+USC Medical Center, Los Angeles, California, USA
| | - Wangxue Chen
- Human Health Therapeutics, National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada
| | - H Howard Xu
- Department of Biological Sciences, California State University Los Angeles, Los Angeles, California, USA
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44
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Smith AD, Wilks A. Differential contributions of the outer membrane receptors PhuR and HasR to heme acquisition in Pseudomonas aeruginosa. J Biol Chem 2015; 290:7756-66. [PMID: 25616666 DOI: 10.1074/jbc.m114.633495] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Pseudomonas aeruginosa PAO1 encodes two outer membrane receptors, PhuR (Pseudomonas heme uptake) and HasR (heme assimilation system). The HasR and PhuR receptors have distinct heme coordinating ligands and substrate specificities. HasR is encoded in an operon with a secreted hemophore, HasAp. In contrast the non-hemophore-dependent PhuR is encoded within an operon along with proteins required for heme translocation into the cytoplasm. Herein we report on the contributions of the HasR and PhuR receptors to heme uptake and utilization. Employing bacterial genetics and isotopic [(13)C]heme labeling studies we have shown both PhuR and HasR are required for optimal heme utilization. However, the unique His-Tyr-ligated PhuR plays a major role in the acquisition of heme. In contrast the HasR receptor plays a primary role in the sensing of extracellular heme and a supplementary role in heme uptake. We propose PhuR and HasR represent non-redundant heme receptors, capable of accessing heme across a wide range of physiological conditions on colonization of the host.
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Affiliation(s)
- Aaron D Smith
- From the Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201
| | - Angela Wilks
- From the Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201
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Fang Z, Sampson SL, Warren RM, Gey van Pittius NC, Newton-Foot M. Iron acquisition strategies in mycobacteria. Tuberculosis (Edinb) 2015; 95:123-30. [PMID: 25636179 DOI: 10.1016/j.tube.2015.01.004] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Revised: 01/01/2015] [Accepted: 01/07/2015] [Indexed: 02/04/2023]
Abstract
Iron is an essential element to most life forms including mycobacterial species. However, in the oxidative atmosphere iron exists as insoluble salts. Free and soluble iron ions are scarce in both the extracellular and intracellular environment which makes iron assimilation very challenging to mycobacteria. Tuberculosis, caused by the pathogen, Mycobacterium tuberculosis, is one of the most infectious and deadly diseases in the world. Extensive studies regarding iron acquisition strategies have been documented in mycobacteria, including work on the mycobacterial iron chelators (siderophores), the iron-responsive regulon, and iron transport and utilization pathways. Under low iron conditions, expression of the genes encoding iron importers, exporters and siderophore biosynthetic enzymes is up-regulated significantly increasing the ability of the bacteria to acquire limited host iron. Disabling these proteins impairs the growth of mycobacteria under low iron conditions both in vitro and in vivo, and that of pathogenic mycobacteria in animal models. Drugs targeting siderophore-mediated iron transport could offer promising therapeutic options. However, the discovery and characterization of an alternative iron acquisition mechanism, the heme transport and utilization pathway, questions the effectiveness of the siderophore-centered therapeutic strategy. Links have been found between these two distinct iron acquisition mechanisms, thus, targeting a few candidate proteins or mechanisms may influence both pathways, leading to effective elimination of the bacteria in the host.
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Affiliation(s)
- Zhuo Fang
- DST/NRF Centre of Excellence in Biomedical Tuberculosis Research, US/MRC Centre for Molecular and Cellular Biology, Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, University of Stellenbosch, Francie van Zijl Drive, Tygerberg, 7505, South Africa.
| | - Samantha Leigh Sampson
- DST/NRF Centre of Excellence in Biomedical Tuberculosis Research, US/MRC Centre for Molecular and Cellular Biology, Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, University of Stellenbosch, Francie van Zijl Drive, Tygerberg, 7505, South Africa.
| | - Robin Mark Warren
- DST/NRF Centre of Excellence in Biomedical Tuberculosis Research, US/MRC Centre for Molecular and Cellular Biology, Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, University of Stellenbosch, Francie van Zijl Drive, Tygerberg, 7505, South Africa.
| | - Nicolaas Claudius Gey van Pittius
- DST/NRF Centre of Excellence in Biomedical Tuberculosis Research, US/MRC Centre for Molecular and Cellular Biology, Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, University of Stellenbosch, Francie van Zijl Drive, Tygerberg, 7505, South Africa.
| | - Mae Newton-Foot
- Division of Medical Microbiology, Department of Pathology, Faculty of Medicine and Health Sciences, University of Stellenbosch, Francie van Zijl Drive, Tygerberg, 7505, South Africa.
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Ascenzi P, di Masi A, Leboffe L, Frangipani E, Nardini M, Verde C, Visca P. Structural Biology of Bacterial Haemophores. Adv Microb Physiol 2015; 67:127-76. [PMID: 26616517 DOI: 10.1016/bs.ampbs.2015.09.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Iron plays a key role in a wide range of metabolic and signalling functions representing an essential nutrient for almost all forms of life. However, the ferric form is hardly soluble, whereas the ferrous form is highly toxic. Thus, in biological fluids, most of the iron is sequestered in iron- or haem-binding proteins and the level of free iron is low, making haem and iron acquisition a challenge for pathogenic bacteria during infections. Although toxic to the host, free haem is a major and readily available source of iron for several pathogenic microorganisms. Both Gram-positive and Gram-negative bacteria have developed several strategies to acquire free haem-Fe and protein-bound haem-Fe. Haemophores are a class of secreted and cell surface-exposed proteins promoting free-haem uptake, haem extraction from host haem proteins, and haem presentation to specific outer-membrane receptors that internalize the metal-porphyrins. Here, structural biology of bacterial haemophores is reviewed focusing on haem acquisition, haem internalization, and haem-degrading systems.
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Affiliation(s)
- Paolo Ascenzi
- Laboratorio Interdipartimentale di Microscopia Elettronica, Università Roma Tre, Roma, Italy; Istituto di Bioscienze e BioRisorse, Consiglio Nazionale delle Ricerche, Napoli, Italy.
| | | | - Loris Leboffe
- Dipartimento di Scienze, Università Roma Tre, Roma, Italy
| | | | - Marco Nardini
- Dipartimento di Bioscienze, Università di Milano, Milano, Italy
| | - Cinzia Verde
- Istituto di Bioscienze e BioRisorse, Consiglio Nazionale delle Ricerche, Napoli, Italy; Dipartimento di Scienze, Università Roma Tre, Roma, Italy
| | - Paolo Visca
- Dipartimento di Scienze, Università Roma Tre, Roma, Italy
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Wu CC, Wang CK, Chen YC, Lin TH, Jinn TR, Lin CT. IscR regulation of capsular polysaccharide biosynthesis and iron-acquisition systems in Klebsiella pneumoniae CG43. PLoS One 2014; 9:e107812. [PMID: 25237815 PMCID: PMC4169559 DOI: 10.1371/journal.pone.0107812] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Accepted: 08/17/2014] [Indexed: 12/29/2022] Open
Abstract
IscR, an Fe–S cluster-containing transcriptional factor, regulates genes involved in various cellular processes. In response to environmental stimuli such as oxidative stress and iron levels, IscR switches between its holo and apo forms to regulate various targets. IscR binding sequences are classified into two types: the type 1 IscR box that is specific for holo-IscR binding, and the type 2 IscR box that binds holo- and apo-IscR. Studying Klebsiella pneumoniae CG43S3, we have previously shown that iron availability regulates capsular polysaccharide (CPS) biosynthesis and iron-acquisition systems. The present study investigated whether IscR is involved in this regulation. Compared with that in CG43S3, the amount of CPS was decreased in AP001 (ΔiscR) or AP002 (iscR3CA), a CG43S3-derived strain expressing mutated IscR mimicked apo-IscR, suggesting that only holo-IscR activates CPS biosynthesis. Furthermore, a promoter-reporter assay verified that the transcription of cps genes was reduced in AP001 and AP002. Purified IscR::His6, but not IscR3CA::His6, was also found to bind the predicted type 1 IscR box specifically in the cps promoter. Furthermore, reduced siderophore production was observed in AP004 (Δfur-ΔiscR) but not in AP005 (Δfur-iscR3CA), implying that apo-IscR activates iron acquisition. Compared with those in AP004, mRNA levels of three putative iron acquisition systems (fhu, iuc, and sit) were increased in AP005, and both purified IscR::His6 and IscR3CA::His6 bound the predicted type 2 IscR box in the fhuA, iucA, and sitA promoters, whereas IscR3CA::His6 displayed a lower affinity. Finally, we analyzed the effect of external iron levels on iscR expression. The transcription of iscR was increased under iron-depleted conditions as well as in AP001 and AP002, suggesting an auto-repression exerted by apo-IscR. Our results show that in K. pneumoniae, IscR plays a dual role in the regulation of CPS biosynthesis and iron-acquisition systems in response to environmental iron availability.
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Affiliation(s)
- Chien-Chen Wu
- Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei, Taiwan, Republic of China
| | - Chien-Kuo Wang
- Department of Biotechnology, Asia University, Taichung, Taiwan, Republic of China
| | - Yu-Ching Chen
- Department of Biomedical Informatics, Asia University, Taichung, Taiwan, Republic of China
| | - Tien-Huang Lin
- Division of Urology, Taichung Tzu Chi Hospital, The Buddhist Tzu Chi Medical Foundation, Taichung, Taiwan, Republic of China
- Graduate Institute of Chinese Medicine, School of Chinese Medicine, China Medical University, Taichung, Taiwan, Republic of China
| | - Tzyy-Rong Jinn
- Graduate Institute of Chinese Medicine, School of Chinese Medicine, China Medical University, Taichung, Taiwan, Republic of China
| | - Ching-Ting Lin
- Graduate Institute of Chinese Medicine, School of Chinese Medicine, China Medical University, Taichung, Taiwan, Republic of China
- * E-mail:
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Affiliation(s)
- Paul A. Sigala
- Departments of Medicine and Molecular Microbiology and the Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, Missouri 63110; ,
| | - Daniel E. Goldberg
- Departments of Medicine and Molecular Microbiology and the Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, Missouri 63110; ,
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Wilks A, Ikeda-Saito M. Heme utilization by pathogenic bacteria: not all pathways lead to biliverdin. Acc Chem Res 2014; 47:2291-8. [PMID: 24873177 PMCID: PMC4139177 DOI: 10.1021/ar500028n] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
The eukaryotic heme oxygenases (HOs) (E.C. 1.14.99.3) convert heme
to biliverdin, iron, and carbon monoxide (CO) in three successive
oxygenation steps. Pathogenic bacteria require iron for survival and
infection. Extracellular heme uptake from the host plays a critical
role in iron acquisition and virulence. In the past decade, several
HOs required for the release of iron from extracellular heme have
been identified in pathogenic bacteria, including Corynebacterium
diphtheriae, Neisseriae meningitides, and Pseudomonas aeruginosa. The
bacterial enzymes were shown to be structurally and mechanistically
similar to those of the canonical eukaryotic HO enzymes. However,
the recent discovery of the structurally and mechanistically distinct
noncanonical heme oxygenases of Staphylococcus aureus and Mycobacterium tuberculosis has
expanded the reaction manifold of heme degradation. The distinct ferredoxin-like
structural fold and extreme heme ruffling are proposed to give rise
to the alternate heme degradation products in the S.
aureus and M. tuberculosis enzymes. In addition, several “heme-degrading factors”
with no structural homology to either class of HOs have recently been
reported. The identification of these “heme-degrading proteins”
has largely been determined on the basis of in vitro heme degradation
assays. Many of these proteins were reported to produce biliverdin,
although no extensive characterization of the products was performed.
Prior to the characterization of the canonical HO enzymes, the nonenzymatic
degradation of heme and heme proteins in the presence of a reductant
such as ascorbate or hydrazine, a reaction termed “coupled
oxidation”, served as a model for biological heme degradation.
However, it was recognized that there were important mechanistic differences
between the so-called coupled oxidation of heme proteins and enzymatic
heme oxygenation. In the coupled oxidation reaction, the final product,
verdoheme, can readily be converted to biliverdin under hydrolytic
conditions. The differences between heme oxygenation by the canonical
and noncanonical HOs and coupled oxidation will be discussed in the
context of the stabilization of the reactive FeIII–OOH
intermediate and regioselective heme hydroxylation. Thus, in the determination
of heme oxygenase activity in vitro, it is important to ensure that
the reaction proceeds through successive oxygenation steps. We further
suggest that when bacterial heme degradation is being characterized,
a systems biology approach combining genetics, mechanistic enzymology,
and metabolite profiling should be undertaken.
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Affiliation(s)
- Angela Wilks
- Department
of Pharmaceutical Sciences, University of Maryland, Baltimore, Maryland 21201-1140, United States
| | - Masao Ikeda-Saito
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University Katahira, Aoba, Sendai 980-8577, Japan
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Bali S, Palmer DJ, Schroeder S, Ferguson SJ, Warren MJ. Recent advances in the biosynthesis of modified tetrapyrroles: the discovery of an alternative pathway for the formation of heme and heme d 1. Cell Mol Life Sci 2014; 71:2837-63. [PMID: 24515122 PMCID: PMC11113276 DOI: 10.1007/s00018-014-1563-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Revised: 12/19/2013] [Accepted: 01/10/2014] [Indexed: 02/05/2023]
Abstract
Hemes (a, b, c, and o) and heme d 1 belong to the group of modified tetrapyrroles, which also includes chlorophylls, cobalamins, coenzyme F430, and siroheme. These compounds are found throughout all domains of life and are involved in a variety of essential biological processes ranging from photosynthesis to methanogenesis. The biosynthesis of heme b has been well studied in many organisms, but in sulfate-reducing bacteria and archaea, the pathway has remained a mystery, as many of the enzymes involved in these characterized steps are absent. The heme pathway in most organisms proceeds from the cyclic precursor of all modified tetrapyrroles uroporphyrinogen III, to coproporphyrinogen III, which is followed by oxidation of the ring and finally iron insertion. Sulfate-reducing bacteria and some archaea lack the genetic information necessary to convert uroporphyrinogen III to heme along the "classical" route and instead use an "alternative" pathway. Biosynthesis of the isobacteriochlorin heme d 1, a cofactor of the dissimilatory nitrite reductase cytochrome cd 1, has also been a subject of much research, although the biosynthetic pathway and its intermediates have evaded discovery for quite some time. This review focuses on the recent advances in the understanding of these two pathways and their surprisingly close relationship via the unlikely intermediate siroheme, which is also a cofactor of sulfite and nitrite reductases in many organisms. The evolutionary questions raised by this discovery will also be discussed along with the potential regulation required by organisms with overlapping tetrapyrrole biosynthesis pathways.
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Affiliation(s)
- Shilpa Bali
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - David J. Palmer
- School of Biosciences, University of Kent, Kent, Canterbury, CT2 7NZ UK
| | - Susanne Schroeder
- School of Biosciences, University of Kent, Kent, Canterbury, CT2 7NZ UK
| | - Stuart J. Ferguson
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - Martin J. Warren
- School of Biosciences, University of Kent, Kent, Canterbury, CT2 7NZ UK
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