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de Assis Noman G, Lacerda de Moura BE, Vieira ML. Leptospiral LipL45 lipoprotein undergoes processing and shares structural similarities with bacterial sigma regulators. Biochem Biophys Res Commun 2024; 717:150057. [PMID: 38718568 DOI: 10.1016/j.bbrc.2024.150057] [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: 02/21/2024] [Revised: 04/23/2024] [Accepted: 05/03/2024] [Indexed: 05/21/2024]
Abstract
Leptospirosis is a widespread zoonotic infectious disease of human and veterinary concern caused by pathogenic spirochetes of the genus Leptospira. To date, little progress towards understanding leptospiral pathogenesis and identification of virulence factors has been made, which is the main bottleneck for developing effective measures against the disease. Some leptospiral proteins, including LipL32, Lig proteins, LipL45, and LipL21, are being considered as potential virulence factors or vaccine candidates. However, their function remains to be established. LipL45 is the most expressed membrane lipoprotein in leptospires, upregulated when the bacteria are transferred to temperatures resembling the host, expressed during infection, suppressed after culture attenuation, and known to suffer processing in vivo and in vitro, generating fragments. Based on body of evidence, we hypothesized that the LipL45 processing might occur by an auto-cleavage event, deriving two fragments. The results presented here, based on bioinformatics, structure modeling analysis, and experimental data, corroborate that LipL45 processing probably includes a self-catalyzed non-proteolytic event and suggest the participation of LipL45 in cell-surface signaling pathways, as the protein shares structural similarities with bacterial sigma regulators. Our data indicate that LipL45 might play an important role in response to environmental conditions, with possible function in the adaptation to the host.
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Affiliation(s)
- Gabriel de Assis Noman
- Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, Brazil; Programa de Pós-graduação Em Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, Brazil.
| | | | - Mônica Larucci Vieira
- Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, Brazil; Programa de Pós-graduação Em Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, Brazil.
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2
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Wang W, Xia J, Wang Z, Shao Z. Bacterial cell sensing and signaling pathway for external polycyclic aromatic hydrocarbons (PAHs). iScience 2023; 26:107912. [PMID: 37841585 PMCID: PMC10570129 DOI: 10.1016/j.isci.2023.107912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 07/19/2023] [Accepted: 09/12/2023] [Indexed: 10/17/2023] Open
Abstract
The mechanism by which a bacterial cell senses external nutrients remains largely unknown. In this study, we identified a bacterial cell sensing system for polycyclic aromatic hydrocarbons (PAHs) in a common marine PAH-using bacterium, Cycloclasticus. It consists of an outer membrane receptor (PahS) and a periplasmic protein (PahP) in combination with a two-component sensing system (TCS) that ensures a rapid response to PAH occurrence by directly controlling serial reactions including chemotactic sensing and movement, PAH uptake and intracellular PAH metabolism. PahS protrudes from the cell and acts as a PAH sensor, transducing the PAH signal across the outer membrane to its periplasmic partner PahP, which in turn transduces the PAH signal across the periplasm to a specialized TCS. This sensing system plays a critical role in sensing and promoting the metabolism of PAHs, which can be scavenged by various hydrocarbon-degrading bacteria.
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Affiliation(s)
- Wanpeng Wang
- Key Laboratory of Marine Genetic Resources, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, China
- Key Laboratory of Marine Genetic Resources of Fujian Province, Xiamen, China
| | - Jingyu Xia
- Key Laboratory of Marine Genetic Resources, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, China
| | - Zining Wang
- Key Laboratory of Marine Genetic Resources, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, China
| | - Zongze Shao
- Key Laboratory of Marine Genetic Resources, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, China
- Key Laboratory of Marine Genetic Resources of Fujian Province, Xiamen, China
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3
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Abstract
TonB-dependent transporters (TBDTs) are present in all gram-negative bacteria and mediate energy-dependent uptake of molecules that are too scarce or large to be taken up efficiently by outer membrane (OM) diffusion channels. This process requires energy that is derived from the proton motive force and delivered to TBDTs by the TonB-ExbBD motor complex in the inner membrane. Together with the need to preserve the OM permeability barrier, this has led to an extremely complex and fascinating transport mechanism for which the fundamentals, despite decades of research, are still unclear. In this review, we describe our current understanding of the transport mechanism of TBDTs, their potential role in the delivery of novel antibiotics, and the important contributions made by TBDT-associated (lipo)proteins.
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Affiliation(s)
- Augustinas Silale
- Biosciences Institute, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom; ,
| | - Bert van den Berg
- Biosciences Institute, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom; ,
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4
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Otero-Asman JR, Sánchez-Jiménez A, Bastiaansen KC, Wettstadt S, Civantos C, García-Puente A, Bitter W, Llamas MA. The Prc and CtpA proteases modulate cell-surface signaling activity and virulence in Pseudomonas aeruginosa. iScience 2023; 26:107216. [PMID: 37534181 PMCID: PMC10392083 DOI: 10.1016/j.isci.2023.107216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 05/17/2023] [Accepted: 06/22/2023] [Indexed: 08/04/2023] Open
Abstract
Cell-surface signaling (CSS) is a signal transfer system of Gram-negative bacteria that produces the activation of an extracytoplasmic function σ factor (σECF) in the cytosol in response to an extracellular signal. Activation requires the regulated and sequential proteolysis of the σECF-associated anti-σ factor, and the function of the Prc and RseP proteases. In this work, we have identified another protease that modulates CSS activity, namely the periplasmic carboxyl-terminal processing protease CtpA. CtpA functions upstream of Prc in the proteolytic cascade and seems to prevent the Prc-mediated proteolysis of the CSS anti-σ factor. Importantly, using zebrafish embryos and the A549 lung epithelial cell line as hosts, we show that mutants in the rseP and ctpA proteases of the human pathogen Pseudomonas aeruginosa are considerably attenuated in virulence while the prc mutation increases virulence likely by enhancing the production of membrane vesicles.
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Affiliation(s)
- Joaquín R. Otero-Asman
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, 18008 Granada, Spain
| | - Ana Sánchez-Jiménez
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, 18008 Granada, Spain
| | - Karlijn C. Bastiaansen
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, 18008 Granada, Spain
- Department of Medical Microbiology and Infection Control, Amsterdam University medical centres, location VU University, 1081 HV Amsterdam, The Netherlands
| | - Sarah Wettstadt
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, 18008 Granada, Spain
| | - Cristina Civantos
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, 18008 Granada, Spain
| | - Alicia García-Puente
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, 18008 Granada, Spain
| | - Wilbert Bitter
- Department of Medical Microbiology and Infection Control, Amsterdam University medical centres, location VU University, 1081 HV Amsterdam, The Netherlands
| | - María A. Llamas
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, 18008 Granada, Spain
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5
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Kristensen SS, Diep DB, Kjos M, Mathiesen G. The role of site-2-proteases in bacteria: a review on physiology, virulence, and therapeutic potential. MICROLIFE 2023; 4:uqad025. [PMID: 37223736 PMCID: PMC10202637 DOI: 10.1093/femsml/uqad025] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 04/21/2023] [Accepted: 05/02/2023] [Indexed: 05/25/2023]
Abstract
Site-2-proteases are a class of intramembrane proteases involved in regulated intramembrane proteolysis. Regulated intramembrane proteolysis is a highly conserved signaling mechanism that commonly involves sequential digestion of an anti-sigma factor by a site-1- and site-2-protease in response to external stimuli, resulting in an adaptive transcriptional response. Variation of this signaling cascade continues to emerge as the role of site-2-proteases in bacteria continues to be explored. Site-2-proteases are highly conserved among bacteria and play a key role in multiple processes, including iron uptake, stress response, and pheromone production. Additionally, an increasing number of site-2-proteases have been found to play a pivotal role in the virulence properties of multiple human pathogens, such as alginate production in Pseudomonas aeruginosa, toxin production in Vibrio cholerae, resistance to lysozyme in enterococci and antimicrobials in several Bacillus spp, and cell-envelope lipid composition in Mycobacterium tuberculosis. The prominent role of site-2-proteases in bacterial pathogenicity highlights the potential of site-2-proteases as novel targets for therapeutic intervention. In this review, we summarize the role of site-2-proteases in bacterial physiology and virulence, as well as evaluate the therapeutic potential of site-2-proteases.
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Affiliation(s)
- Sofie S Kristensen
- Faculty of Chemistry, Biotechnology, and Food Science, Norwegian University of Life Sciences (NMBU), 1433 Ås, Norway
| | | | - Morten Kjos
- Corresponding author. NMBU, P.O. Box 5003, 1433 Ås, Norway. E-mail:
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6
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Sánchez-Jiménez A, Marcos-Torres FJ, Llamas MA. Mechanisms of iron homeostasis in Pseudomonas aeruginosa and emerging therapeutics directed to disrupt this vital process. Microb Biotechnol 2023. [PMID: 36857468 DOI: 10.1111/1751-7915.14241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 02/13/2023] [Indexed: 03/03/2023] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen able to infect any human tissue. One of the reasons for its high adaptability and colonization of host tissues is its capacity of maintaining iron homeostasis through a wide array of iron acquisition and removal mechanisms. Due to their ability to cause life-threatening acute and chronic infections, especially among cystic fibrosis and immunocompromised patients, and their propensity to acquire resistance to many antibiotics, the World Health Organization (WHO) has encouraged the scientific community to find new strategies to eradicate this pathogen. Several recent strategies to battle P. aeruginosa focus on targeting iron homeostasis mechanisms, turning its greatest advantage into an exploitable weak point. In this review, we discuss the different mechanisms used by P. aeruginosa to maintain iron homeostasis and the strategies being developed to fight this pathogen by blocking these mechanisms. Among others, the use of iron chelators and mimics, as well as disruption of siderophore production and uptake, have shown promising results in reducing viability and/or virulence of this pathogen. The so-called 'Trojan-horse' strategy taking advantage of the siderophore uptake systems is emerging as an efficient method to improve delivery of antibiotics into the bacterial cells. Moreover, siderophore transporters are considered promising targets for the developing of P. aeruginosa vaccines.
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Affiliation(s)
- Ana Sánchez-Jiménez
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Francisco J Marcos-Torres
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - María A Llamas
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
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7
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Sugue MF, Burdur AN, Ringel MT, Dräger G, Brüser T. PvdM of fluorescent pseudomonads is required for the oxidation of ferribactin by PvdP in periplasmic pyoverdine maturation. J Biol Chem 2022; 298:102201. [PMID: 35764171 PMCID: PMC9305348 DOI: 10.1016/j.jbc.2022.102201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Revised: 06/21/2022] [Accepted: 06/22/2022] [Indexed: 11/16/2022] Open
Abstract
Fluorescent pseudomonads such as Pseudomonas aeruginosa or Pseudomonas fluorescens produce pyoverdine siderophores that ensure iron-supply in iron-limited environments. After its synthesis in the cytoplasm, the nonfluorescent pyoverdine precursor ferribactin is exported into the periplasm, where the enzymes PvdQ, PvdP, PvdO, PvdN, and PtaA are responsible for fluorophore maturation and tailoring steps. While the roles of all these enzymes are clear, little is known about the role of PvdM, a human renal dipeptidase–related protein that is predicted to be periplasmic and that is essential for pyoverdine biogenesis. Here, we reveal the subcellular localization and functional role of PvdM. Using the model organism P. fluorescens, we show that PvdM is anchored to the periplasmic side of the cytoplasmic membrane, where it is indispensable for the activity of the tyrosinase PvdP. While PvdM does not share the metallopeptidase function of renal dipeptidase, it still has the corresponding peptide-binding site. The substrate of PvdP, deacylated ferribactin, is secreted by a ΔpvdM mutant strain, indicating that PvdM prevents loss of this periplasmic biosynthesis intermediate into the medium by ensuring the efficient transfer of ferribactin to PvdP in vivo. We propose that PvdM belongs to a new dipeptidase-related protein subfamily with inactivated Zn2+ coordination sites, members of which are usually genetically linked to TonB-dependent uptake systems and often associated with periplasmic FAD-dependent oxidoreductases related to d-amino acid oxidases. We suggest that these proteins are necessary for selective binding, exposure, or transfer of specific d- and l-amino acid–containing peptides and other periplasmic biomolecules in manifold pathways.
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Affiliation(s)
| | - Ali Nazmi Burdur
- Institute of Microbiology, Leibniz University Hannover, Hannover, Germany
| | - Michael T Ringel
- Institute of Microbiology, Leibniz University Hannover, Hannover, Germany
| | - Gerald Dräger
- Institute of Organic Chemistry, Leibniz University Hannover, Schneiderberg 1 B, 30167 Hannover, Germany
| | - Thomas Brüser
- Institute of Microbiology, Leibniz University Hannover, Hannover, Germany.
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8
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Braun V, Hartmann MD, Hantke K. Transcription regulation of iron carrier transport genes by ECF sigma factors through signaling from the cell surface into the cytoplasm. FEMS Microbiol Rev 2022; 46:6524835. [PMID: 35138377 PMCID: PMC9249621 DOI: 10.1093/femsre/fuac010] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 01/26/2022] [Accepted: 02/07/2022] [Indexed: 12/02/2022] Open
Abstract
Bacteria are usually iron-deficient because the Fe3+ in their environment is insoluble or is incorporated into proteins. To overcome their natural iron limitation, bacteria have developed sophisticated iron transport and regulation systems. In gram-negative bacteria, these include iron carriers, such as citrate, siderophores, and heme, which when loaded with Fe3+ adsorb with high specificity and affinity to outer membrane proteins. Binding of the iron carriers to the cell surface elicits a signal that initiates transcription of iron carrier transport and synthesis genes, referred to as “cell surface signaling”. Transcriptional regulation is not coupled to transport. Outer membrane proteins with signaling functions contain an additional N-terminal domain that in the periplasm makes contact with an anti-sigma factor regulatory protein that extends from the outer membrane into the cytoplasm. Binding of the iron carriers to the outer membrane receptors elicits proteolysis of the anti-sigma factor by two different proteases, Prc in the periplasm, and RseP in the cytoplasmic membrane, inactivates the anti-sigma function or results in the generation of an N-terminal peptide of ∼50 residues with pro-sigma activity yielding an active extracytoplasmic function (ECF) sigma factor. Signal recognition and signal transmission into the cytoplasm is discussed herein.
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Affiliation(s)
- Volkmar Braun
- Max Planck Institute for Biology, Department of Protein Evolution, Max Planck Ring 5, 72076 Tübingen, Germany
| | - Marcus D Hartmann
- Max Planck Institute for Biology, Department of Protein Evolution, Max Planck Ring 5, 72076 Tübingen, Germany
| | - Klaus Hantke
- IMIT Institute, University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
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9
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Iron Homeostasis in Pseudomonas aeruginosa: Targeting Iron Acquisition and Storage as an Antimicrobial Strategy. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1386:29-68. [DOI: 10.1007/978-3-031-08491-1_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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10
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Extracellular haem utilization by the opportunistic pathogen Pseudomonas aeruginosa and its role in virulence and pathogenesis. Adv Microb Physiol 2021; 79:89-132. [PMID: 34836613 DOI: 10.1016/bs.ampbs.2021.07.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Iron is an essential micronutrient for all bacteria but presents a significant challenge given its limited bioavailability. Furthermore, iron's toxicity combined with the need to maintain iron levels within a narrow physiological range requires integrated systems to sense, regulate and transport a variety of iron complexes. Most bacteria encode systems to chelate and transport ferric iron (Fe3+) via siderophore receptor mediated uptake or via cytoplasmic energy dependent transport systems. Pathogenic bacteria have further lowered the barrier to iron acquisition by employing systems to utilize haem as a source of iron. Haem, a lipophilic and toxic molecule, presents a significant challenge for transport into the cell. As such pathogenic bacteria have evolved sophisticated cell surface signaling (CSS) and transport systems to sense and obtain haem from the host. Once internalized haem is cleaved by both oxidative and non-oxidative mechanisms to release iron. Herein we summarize our current understanding of the mechanism of haem sensing, uptake and utilization in Pseudomonas aeruginosa, its role in pathogenesis and virulence, and the potential of these systems as antimicrobial targets.
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11
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Yokoyama T, Niinae T, Tsumagari K, Imami K, Ishihama Y, Hizukuri Y, Akiyama Y. The Escherichia coli S2P intramembrane protease RseP regulates ferric citrate uptake by cleaving the sigma factor regulator FecR. J Biol Chem 2021; 296:100673. [PMID: 33865858 PMCID: PMC8144685 DOI: 10.1016/j.jbc.2021.100673] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 04/08/2021] [Accepted: 04/14/2021] [Indexed: 02/03/2023] Open
Abstract
Escherichia coli RseP, a member of the site-2 protease family of intramembrane proteases, is involved in the activation of the σE extracytoplasmic stress response and elimination of signal peptides from the cytoplasmic membrane. However, whether RseP has additional cellular functions is unclear. In this study, we used mass spectrometry-based quantitative proteomic analysis to search for new substrates that might reveal unknown physiological roles for RseP. Our data showed that the levels of several Fec system proteins encoded by the fecABCDE operon (fec operon) were significantly decreased in an RseP-deficient strain. The Fec system is responsible for the uptake of ferric citrate, and the transcription of the fec operon is controlled by FecI, an alternative sigma factor, and its regulator FecR, a single-pass transmembrane protein. Assays with a fec operon expression reporter demonstrated that the proteolytic activity of RseP is essential for the ferric citrate-dependent upregulation of the fec operon. Analysis using the FecR protein and FecR-derived model proteins showed that FecR undergoes sequential processing at the membrane and that RseP participates in the last step of this sequential processing to generate the N-terminal cytoplasmic fragment of FecR that participates in the transcription of the fec operon with FecI. A shortened FecR construct was not dependent on RseP for activation, confirming this cleavage step is the essential and sufficient role of RseP. Our study unveiled that E. coli RseP performs the intramembrane proteolysis of FecR, a novel physiological role that is essential for regulating iron uptake by the ferric citrate transport system.
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Affiliation(s)
- Tatsuhiko Yokoyama
- Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto, Japan
| | - Tomoya Niinae
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
| | - Kazuya Tsumagari
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
| | - Koshi Imami
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
| | - Yasushi Ishihama
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
| | - Yohei Hizukuri
- Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto, Japan.
| | - Yoshinori Akiyama
- Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto, Japan.
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12
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Cunrath O, Graulier G, Carballido-Lopez A, Pérard J, Forster A, Geoffroy VA, Saint Auguste P, Bumann D, Mislin GLA, Michaud-Soret I, Schalk IJ, Fechter P. The pathogen Pseudomonas aeruginosa optimizes the production of the siderophore pyochelin upon environmental challenges. Metallomics 2020; 12:2108-2120. [PMID: 33355556 DOI: 10.1039/d0mt00029a] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Siderophores are iron chelators produced by bacteria to access iron, an essential nutrient. The pathogen Pseudomonas aeruginosa produces two siderophores, pyoverdine and pyochelin, the former with a high affinity for iron and the latter with a lower affinity. Furthermore, the production of both siderophores involves a positive auto-regulatory loop: the presence of the ferri-siderophore complex is essential for their large production. Since pyochelin has a lower affinity for iron it was hard to consider the role of pyochelin in drastic competitive environments where the host or the environmental microbiota produce strong iron chelators and may inhibit iron chelation by pyochelin. We showed here that the pyochelin pathway overcomes this difficulty through a more complex regulating mechanism for pyochelin production than previously described. Indeed, in the absence of pyoverdine, and thus higher difficulty to access iron, the bacteria are able to produce pyochelin independently of the presence of ferri-pyochelin. The regulation of the pyochelin pathway appeared to be more complex than expected with a more intricate tuning between repression and activation. Consequently, when the bacteria cannot produce pyoverdine they are able to produce pyochelin even in the presence of strong iron chelators. Such results support a more complex and varied role for this siderophore than previously described, and complexify the battle for iron during P. aeruginosa infection.
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Affiliation(s)
- Olivier Cunrath
- Université de Strasbourg, UMR7242, ESBS, Bld Sébastien Brant, F-67413 Illkirch, Strasbourg, France.
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13
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Heywood A, Lamont IL. Cell envelope proteases and peptidases of Pseudomonas aeruginosa: multiple roles, multiple mechanisms. FEMS Microbiol Rev 2020; 44:857-873. [PMID: 32804218 DOI: 10.1093/femsre/fuaa036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2020] [Accepted: 08/05/2020] [Indexed: 12/15/2022] Open
Abstract
Pseudomonas aeruginosa is a Gram-negative bacterium that is commonly isolated from damp environments. It is also a major opportunistic pathogen, causing a wide range of problematic infections. The cell envelope of P. aeruginosa, comprising the cytoplasmic membrane, periplasmic space, peptidoglycan layer and outer membrane, is critical to the bacteria's ability to adapt and thrive in a wide range of environments. Over 40 proteases and peptidases are located in the P. aeruginosa cell envelope. These enzymes play many crucial roles. They are required for protein secretion out of the cytoplasm to the periplasm, outer membrane, cell surface or the environment; for protein quality control and removal of misfolded proteins; for controlling gene expression, allowing adaptation to environmental changes; for modification and remodelling of peptidoglycan; and for metabolism of small molecules. The key roles of cell envelope proteases in ensuring normal cell functioning have prompted the development of inhibitors targeting some of these enzymes as potential new anti-Pseudomonas therapies. In this review, we summarise the current state of knowledge across the breadth of P. aeruginosa cell envelope proteases and peptidases, with an emphasis on recent findings, and highlight likely future directions in their study.
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Affiliation(s)
- Astra Heywood
- Department of Biochemistry, University of Otago, Dunedin 9054, New Zealand
| | - Iain L Lamont
- Department of Biochemistry, University of Otago, Dunedin 9054, New Zealand
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14
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Normant V, Josts I, Kuhn L, Perraud Q, Fritsch S, Hammann P, Mislin GLA, Tidow H, Schalk IJ. Nocardamine-Dependent Iron Uptake in Pseudomonas aeruginosa: Exclusive Involvement of the FoxA Outer Membrane Transporter. ACS Chem Biol 2020; 15:2741-2751. [PMID: 32902248 DOI: 10.1021/acschembio.0c00535] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Iron is a key nutrient for almost all living organisms. Paradoxically, it is poorly soluble and consequently poorly bioavailable. Bacteria have thus developed multiple strategies to access this metal. One of the most common consists of the use of siderophores, small compounds that chelate ferric iron with very high affinity. Many bacteria are able to produce their own siderophores or use those produced by other microorganisms (exosiderophores) in a piracy strategy. Pseudomonas aeruginosa produces two siderophores, pyoverdine and pyochelin, and is also able to use a large panel of exosiderophores. We investigated the ability of P. aeruginosa to use nocardamine (NOCA) and ferrioxamine B (DFOB) as exosiderophores under iron-limited planktonic growth conditions. Proteomic and RT-qPCR approaches showed induction of the transcription and expression of the outer membrane transporter FoxA in the presence of NOCA or DFOB in the bacterial environment. Expression of the proteins of the heme- or pyoverdine- and pyochelin-dependent iron uptake pathways was not affected by the presence of these two tris-hydroxamate siderophores. 55Fe uptake assays using foxA mutants showed ferri-NOCA to be exclusively transported by FoxA, whereas ferri-DFOB was transported by FoxA and at least one other unidentified transporter. The crystal structure of FoxA complexed with NOCA-Fe revealed very similar siderophore binding sites between NOCA-Fe and DFOB-Fe. We discuss iron uptake by hydroxamate exosiderophores in P. aeruginosa cells in light of these results.
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Affiliation(s)
- Vincent Normant
- CNRS, UMR7242, ESBS, Université de Strasbourg, Bld Sébastien Brant, F-67412 Illkirch, France
| | - Inokentijs Josts
- The Hamburg Centre for Ultrafast Imaging, University of Hamburg, Hamburg, Germany
- Department of Chemistry, Institute for Biochemistry and Molecular Biology, University of Hamburg, Hamburg, Germany
| | - Lauriane Kuhn
- Plateforme Proteomique Strasbourg - Esplanade, Institut de Biologie Moléculaire et Cellulaire, CNRS, FR1589, 15 rue Descartes, F-67084 Strasbourg Cedex, France
| | - Quentin Perraud
- CNRS, UMR7242, ESBS, Université de Strasbourg, Bld Sébastien Brant, F-67412 Illkirch, France
| | - Sarah Fritsch
- CNRS, UMR7242, ESBS, Université de Strasbourg, Bld Sébastien Brant, F-67412 Illkirch, France
| | - Philippe Hammann
- Plateforme Proteomique Strasbourg - Esplanade, Institut de Biologie Moléculaire et Cellulaire, CNRS, FR1589, 15 rue Descartes, F-67084 Strasbourg Cedex, France
| | - Gaëtan L. A. Mislin
- CNRS, UMR7242, ESBS, Université de Strasbourg, Bld Sébastien Brant, F-67412 Illkirch, France
| | - Henning Tidow
- The Hamburg Centre for Ultrafast Imaging, University of Hamburg, Hamburg, Germany
- Department of Chemistry, Institute for Biochemistry and Molecular Biology, University of Hamburg, Hamburg, Germany
| | - Isabelle J. Schalk
- CNRS, UMR7242, ESBS, Université de Strasbourg, Bld Sébastien Brant, F-67412 Illkirch, France
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15
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Wettstadt S, Llamas MA. Role of Regulated Proteolysis in the Communication of Bacteria With the Environment. Front Mol Biosci 2020; 7:586497. [PMID: 33195433 PMCID: PMC7593790 DOI: 10.3389/fmolb.2020.586497] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 09/22/2020] [Indexed: 12/29/2022] Open
Abstract
For bacteria to flourish in different niches, they need to sense signals from the environment and translate these into appropriate responses. Most bacterial signal transduction systems involve proteins that trigger the required response through the modification of gene transcription. These proteins are often produced in an inactive state that prevents their interaction with the RNA polymerase and/or the DNA in the absence of the inducing signal. Among other mechanisms, regulated proteolysis is becoming increasingly recognized as a key process in the modulation of the activity of these signal response proteins. Regulated proteolysis can either produce complete degradation or specific cleavage of the target protein, thus modifying its function. Because proteolysis is a fast process, the modulation of signaling proteins activity by this process allows for an immediate response to a given signal, which facilitates adaptation to the surrounding environment and bacterial survival. Moreover, regulated proteolysis is a fundamental process for the transmission of extracellular signals to the cytosol through the bacterial membranes. By a proteolytic mechanism known as regulated intramembrane proteolysis (RIP) transmembrane proteins are cleaved within the plane of the membrane to liberate a cytosolic domain or protein able to modify gene transcription. This allows the transmission of a signal present on one side of a membrane to the other side where the response is elicited. In this work, we review the role of regulated proteolysis in the bacterial communication with the environment through the modulation of the main bacterial signal transduction systems, namely one- and two-component systems, and alternative σ factors.
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Affiliation(s)
- Sarah Wettstadt
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - María A Llamas
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
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16
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Jensen JL, Jernberg BD, Sinha SC, Colbert CL. Structural basis of cell-surface signaling by a conserved sigma regulator in Gram-negative bacteria. J Biol Chem 2020; 295:5795-5806. [PMID: 32107313 PMCID: PMC7186176 DOI: 10.1074/jbc.ra119.010697] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 02/23/2020] [Indexed: 01/07/2023] Open
Abstract
Cell-surface signaling (CSS) in Gram-negative bacteria involves highly conserved regulatory pathways that optimize gene expression by transducing extracellular environmental signals to the cytoplasm via inner-membrane sigma regulators. The molecular details of ferric siderophore-mediated activation of the iron import machinery through a sigma regulator are unclear. Here, we present the 1.56 Å resolution structure of the periplasmic complex of the C-terminal CSS domain (CCSSD) of PupR, the sigma regulator in the Pseudomonas capeferrum pseudobactin BN7/8 transport system, and the N-terminal signaling domain (NTSD) of PupB, an outer-membrane TonB-dependent transducer. The structure revealed that the CCSSD consists of two subdomains: a juxta-membrane subdomain, which has a novel all-β-fold, followed by a secretin/TonB, short N-terminal subdomain at the C terminus of the CCSSD, a previously unobserved topological arrangement of this domain. Using affinity pulldown assays, isothermal titration calorimetry, and thermal denaturation CD spectroscopy, we show that both subdomains are required for binding the NTSD with micromolar affinity and that NTSD binding improves CCSSD stability. Our findings prompt us to present a revised model of CSS wherein the CCSSD:NTSD complex forms prior to ferric-siderophore binding. Upon siderophore binding, conformational changes in the CCSSD enable regulated intramembrane proteolysis of the sigma regulator, ultimately resulting in transcriptional regulation.
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Affiliation(s)
- Jaime L Jensen
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108
| | - Beau D Jernberg
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108
| | - Sangita C Sinha
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108
| | - Christopher L Colbert
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108.
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17
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Otero-Asman JR, Quesada JM, Jim KK, Ocampo-Sosa A, Civantos C, Bitter W, Llamas MA. The extracytoplasmic function sigma factor σ VreI is active during infection and contributes to phosphate starvation-induced virulence of Pseudomonas aeruginosa. Sci Rep 2020; 10:3139. [PMID: 32081993 PMCID: PMC7035377 DOI: 10.1038/s41598-020-60197-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2019] [Accepted: 02/07/2020] [Indexed: 12/27/2022] Open
Abstract
The extracytoplasmic function sigma factor σVreI of the human pathogen Pseudomonas aeruginosa promotes transcription of potential virulence determinants, including secretion systems and secreted proteins. Its activity is modulated by the VreR anti-σ factor that inhibits the binding of σVreI to the RNA polymerase in the absence of a (still unknown) inducing signal. The vreI-vreR genes are expressed under inorganic phosphate (Pi) starvation, a physiological condition often encountered in the host that increases P. aeruginosa pathogenicity. However, whether or not σVreI is active in vivo during infection and contributes to the Pi starvation-induced virulence of this pathogen has not been analyzed yet. Using zebrafish embryos and a human alveolar basal epithelial cell line as P. aeruginosa hosts, we demonstrate in this work that σVreI is active during infection and that lack of σVreI considerably reduces the Pi starvation-induced virulence of this pathogen. Surprisingly, lack of the σVreI inhibitor, the VreR anti-σ factor, also diminishes the virulence of P. aeruginosa. By transcriptomic analyses we show that VreR modulates gene expression not only in a σVreI-dependent but also in a σVreI-independent manner. This includes potential virulence determinants and transcriptional regulators that could be responsible for the reduced virulence of the ΔvreR mutant.
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Affiliation(s)
- Joaquín R Otero-Asman
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - José M Quesada
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Kin K Jim
- Department of Medical Microbiology and Infection Control, Amsterdam University medical centers, location VU University, Amsterdam, The Netherlands
| | - Alain Ocampo-Sosa
- Service of Microbiology, Hospital Universitario Marqués de Valdecilla-Instituto de Investigación Sanitaria Valdecilla, Santander, Spain
| | - Cristina Civantos
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Wilbert Bitter
- Department of Medical Microbiology and Infection Control, Amsterdam University medical centers, location VU University, Amsterdam, The Netherlands
| | - María A Llamas
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain.
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18
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Schalk IJ, Rigouin C, Godet J. An overview of siderophore biosynthesis among fluorescent Pseudomonads and new insights into their complex cellular organization. Environ Microbiol 2020; 22:1447-1466. [PMID: 32011068 DOI: 10.1111/1462-2920.14937] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 01/25/2020] [Accepted: 01/28/2020] [Indexed: 01/02/2023]
Abstract
Siderophores are iron-chelating molecules produced by bacteria to access iron, a key nutrient. These compounds have highly diverse chemical structures, with various chelating groups. They are released by bacteria into their environment to scavenge iron and bring it back into the cells. The biosynthesis of siderophores requires complex enzymatic processes and expression of the enzymes involved is very finely regulated by iron availability and diverse transcriptional regulators. Recent data have also highlighted the organization of the enzymes involved in siderophore biosynthesis into siderosomes, multi-enzymatic complexes involved in siderophore synthesis. An understanding of siderophore biosynthesis is of great importance, as these compounds have many potential biotechnological applications because of their metal-chelating properties and their key role in bacterial growth and virulence. This review focuses on the biosynthesis of siderophores produced by fluorescent Pseudomonads, bacteria capable of colonizing a large variety of ecological niches. They are characterized by the production of chromopeptide siderophores, called pyoverdines, which give the typical green colour characteristic of fluorescent pseudomonad cultures. Secondary siderophores are also produced by these strains and can have highly diverse structures (such as pyochelins, pseudomonine, yersiniabactin, corrugatin, achromobactin and quinolobactin).
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Affiliation(s)
- Isabelle J Schalk
- CNRS, UMR7242, ESBS, Illkirch, Strasbourg, France.,Université de Strasbourg, UMR7242, ESBS, Illkirch, Strasbourg, France
| | - Coraline Rigouin
- CNRS, UMR7242, ESBS, Illkirch, Strasbourg, France.,Université de Strasbourg, UMR7242, ESBS, Illkirch, Strasbourg, France
| | - Julien Godet
- Université de Strasbourg, Laboratoire de BioImagerie et Pathologies, UMR CNRS, 7021, Illkirch, France
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19
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Otero-Asman JR, García-García AI, Civantos C, Quesada JM, Llamas MA. Pseudomonas aeruginosa possesses three distinct systems for sensing and using the host molecule haem. Environ Microbiol 2019; 21:4629-4647. [PMID: 31390127 DOI: 10.1111/1462-2920.14773] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 08/05/2019] [Indexed: 12/18/2022]
Abstract
Pathogens have developed several strategies to obtain iron during infection, including the use of iron-containing molecules from the host. Haem accounts for the vast majority of the iron pool in vertebrates and thus represents an important source of iron for pathogens. Using a proteomic approach, we have identified in this work a previously uncharacterized system, which we name Hxu, that together with the known Has and Phu systems, is used by the human pathogen Pseudomonas aeruginosa to respond to haem. We show that the Has and Hxu systems are functional signal transduction pathways of the cell-surface signalling class and report the mechanism triggering the activation of these signalling systems. Both signalling cascades involve an outer membrane receptor (HasR and HxuA respectively) that upon sensing haem in the extracellular medium produces the activation of an σECF factor in the cytosol. HxuA has a major role in signalling and a minor role in haem acquisition in conditions in which the HasR and PhuR receptors or other sources of iron are present. Remarkably, P. aeruginosa compensates the lack of the HasR receptor by increasing the production of HxuA, which underscores the importance of haem signalling for this pathogen.
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Affiliation(s)
- Joaquín R Otero-Asman
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, 18008, Granada, Spain
| | - Ana I García-García
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, 18008, Granada, Spain
| | - Cristina Civantos
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, 18008, Granada, Spain
| | - José M Quesada
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, 18008, Granada, Spain
| | - María A Llamas
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, 18008, Granada, Spain
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20
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Zuniga-Soto E, Fitzpatrick DA, Doohan FM, Mullins E. Insights into the transcriptomic response of the plant engineering bacterium Ensifer adhaerens OV14 during transformation. Sci Rep 2019; 9:10344. [PMID: 31316079 PMCID: PMC6637203 DOI: 10.1038/s41598-019-44648-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 05/08/2019] [Indexed: 11/08/2022] Open
Abstract
The ability to engineer plant genomes has been primarily driven by the soil bacterium Agrobacterium tumefaciens but recently the potential of alternative rhizobia such as Rhizobium etli and Ensifer adhaerens OV14, the latter of which supports Ensifer Mediated Transformation (EMT) has been reported. Surprisingly, a knowledge deficit exists in regards to understanding the whole genome processes underway in plant transforming bacteria, irrespective of the species. To begin to address the issue, we undertook a temporal RNAseq-based profiling study of E. adhaerens OV14 in the presence/absence of Arabidopsis thaliana tissues. Following co-cultivation with root tissues, 2333 differentially expressed genes (DEGs) were noted. Meta-analysis of the RNAseq data sets identified a clear shift from plasmid-derived gene expression to chromosomal-based transcription within the early stages of bacterium-plant co-cultivation. During this time, the number of differentially expressed prokaryotic genes increased steadily out to 7 days co-cultivation, a time at which optimum rates of transformation were observed. Gene ontology evaluations indicated a role for both chromosomal and plasmid-based gene families linked specifically with quorum sensing, flagellin production and biofilm formation in the process of EMT. Transcriptional evaluation of vir genes, housed on the pCAMBIA 5105 plasmid in E. adhaerens OV14 confirmed the ability of E. adhaerens OV14 to perceive and activate its transcriptome in response to the presence of 200 µM of acetosyringone. Significantly, this is the first study to characterise the whole transcriptomic response of a plant engineering bacterium in the presence of plant tissues and provides a novel insight into prokaryotic genetic processes that support T-DNA transfer.
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Affiliation(s)
- Evelyn Zuniga-Soto
- Department of Crop Science, Teagasc Crops Research Centre, Oak Park, Carlow, Ireland
- School of Biology and Environmental Sciences, University College Dublin, Belfield, Dublin 4, Ireland
| | - David A Fitzpatrick
- Department of Biology, National University of Ireland Maynooth, Maynooth, Ireland
| | - Fiona M Doohan
- School of Biology and Environmental Sciences, University College Dublin, Belfield, Dublin 4, Ireland
| | - Ewen Mullins
- Department of Crop Science, Teagasc Crops Research Centre, Oak Park, Carlow, Ireland.
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21
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Otero-Asman JR, Wettstadt S, Bernal P, Llamas MA. Diversity of extracytoplasmic function sigma (σ ECF ) factor-dependent signaling in Pseudomonas. Mol Microbiol 2019; 112:356-373. [PMID: 31206859 DOI: 10.1111/mmi.14331] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/10/2019] [Indexed: 12/23/2022]
Abstract
Pseudomonas bacteria are widespread and are found in soil and water, as well as pathogens of both plants and animals. The ability of Pseudomonas to colonize many different environments is facilitated by the multiple signaling systems these bacteria contain that allow Pseudomonas to adapt to changing circumstances by generating specific responses. Among others, signaling through extracytoplasmic function σ (σECF ) factors is extensively present in Pseudomonas. σECF factors trigger expression of functions required under particular conditions in response to specific signals. This manuscript reviews the phylogeny and biological roles of σECF factors in Pseudomonas, and highlights the diversity of σECF -signaling pathways of this genus in terms of function and activation. We show that Pseudomonas σECF factors belong to 16 different phylogenetic groups. Most of them are included within the iron starvation group and are mainly involved in iron acquisition. The second most abundant group is formed by RpoE-like σECF factors, which regulate the responses to cell envelope stress. Other groups controlling solvent tolerance, biofilm formation and the response to oxidative stress, among other functions, are present in lower frequency. The role of σECF factors in the virulence of Pseudomonas pathogenic species is described.
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Affiliation(s)
- Joaquín R Otero-Asman
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Sarah Wettstadt
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Patricia Bernal
- Department of Biology, Faculty of Sciences, Universidad Autónoma de Madrid, Madrid, Spain
| | - María A Llamas
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
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22
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Casas Garcia GP, Perugini MA, Lamont IL, Maher MJ. The purification of the σ FpvI/FpvR 20 and σ PvdS/FpvR 20 protein complexes is facilitated at room temperature. Protein Expr Purif 2019; 160:11-18. [PMID: 30878602 DOI: 10.1016/j.pep.2019.03.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 03/07/2019] [Accepted: 03/11/2019] [Indexed: 10/27/2022]
Abstract
Bacteria contain sigma (σ) factors that control gene expression in response to various environmental stimuli. The alternative sigma factors σFpvI and σPvdS bind specifically to the antisigma factor FpvR. These proteins are an essential component of the pyoverdine-based system for iron uptake in Pseudomonas aeruginosa. Due to the uniqueness of this system, where the activities of both the σFpvI and σPvdS sigma factors are regulated by the same antisigma factor, the interactions between the antisigma protein FpvR20 and the σFpvI and σPvdS proteins have been widely studied in vivo. However, difficulties in obtaining soluble, recombinant preparations of the σFpvI and σPvdS proteins have limited their biochemical and structural characterizations. In this study, we describe a purification protocol that resulted in the production of soluble, recombinant His6-σFpvI/FpvR1-67, His6-σFpvI/FpvR1-89, His6-σPvdS/FpvR1-67 and His6-σPvdS/FpvR1-89 protein complexes (where FpvR1-67 and FpvR1-89 are truncated versions of FpvR20) at high purities and concentrations, appropriate for biophysical analyses by circular dichroism spectroscopy and analytical ultracentrifugation. These results showed the proteins to be folded in solution and led to the determination of the affinities of the protein-protein interactions within the His6-σFpvI/FpvR1-67 and His6-σPvdS/FpvR1-67 complexes. A comparison of these values with those previously reported for the His6-σFpvI/FpvR1-89 and His6-σPvdS/FpvR1-89 complexes is made.
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Affiliation(s)
- G Patricia Casas Garcia
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Matthew A Perugini
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Iain L Lamont
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Megan J Maher
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia.
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23
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Ringel MT, Brüser T. The biosynthesis of pyoverdines. MICROBIAL CELL (GRAZ, AUSTRIA) 2018; 5:424-437. [PMID: 30386787 PMCID: PMC6206403 DOI: 10.15698/mic2018.10.649] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 07/03/2018] [Indexed: 01/11/2023]
Abstract
Pyoverdines are fluorescent siderophores of pseudomonads that play important roles for growth under iron-limiting conditions. The production of pyoverdines by fluorescent pseudomonads permits their colonization of hosts ranging from humans to plants. Prominent examples include pathogenic or non-pathogenic species such as Pseudomonas aeruginosa, P. putida, P. syringae, or P. fluorescens. Many distinct pyoverdines have been identified, all of which have a dihydroxyquinoline fluorophore in common, derived from oxidative cyclizations of non-ribosomal peptides. These serve as precursor of pyoverdines and are commonly known as ferribactins. Ferribactins of distinct species or even strains often differ in their sequence, resulting in a large variety of pyoverdines. However, synthesis of all ferribactins begins with an L-Glu/D-Tyr/L-Dab sequence, and the fluorophore is generated from the D-Tyr/L-Dab residues. In addition, the initial L-Glu residue is modified to various acids and amides that are responsible for the range of distinguishable pyoverdines in individual strains. While ferribactin synthesis is a cytoplasmic process, the maturation to the fluorescent pyoverdine as well as the tailoring of the initial glutamate are exclusively periplasmic processes that have been a mystery until recently. Here we review the current knowledge of pyoverdine biosynthesis with a focus on the recent advancements regarding the periplasmic maturation and tailoring reactions.
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Affiliation(s)
- Michael T. Ringel
- Institute of Microbiology, Leibniz University Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany
| | - Thomas Brüser
- Institute of Microbiology, Leibniz University Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany
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24
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Bishop TF, Martin LW, Lamont IL. Activation of a Cell Surface Signaling Pathway in Pseudomonas aeruginosa Requires ClpP Protease and New Sigma Factor Synthesis. Front Microbiol 2017; 8:2442. [PMID: 29312164 PMCID: PMC5733041 DOI: 10.3389/fmicb.2017.02442] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 11/24/2017] [Indexed: 11/13/2022] Open
Abstract
Extracytoplasmic function (ECF) sigma factors control expression of large numbers of genes in bacteria. Most ECF sigma factors are inhibited by antisigma proteins, with inhibition being relieved by environmental signals that lead to inactivation of the antisigma protein and consequent sigma factor activity. In cell surface signaling (CSS) systems in Gram negative bacteria antisigma activity is controlled by an outer membrane protein receptor and its ligand. In Pseudomonas aeruginosa one such system controls expression of genes for secretion and uptake of a siderophore, pyoverdine. In this system the activities of two sigma factors σFpvI and σPvdS are inhibited by antisigma protein FpvR20 that binds to the sigma factors, preventing their interaction with core RNA polymerase. Transport of ferripyoverdine by its outer membrane receptor FpvA causes proteolytic degradation of FpvR20, inducing expression of σFpvI- and σPvdS-dependent target genes. Here we show that degradation of FpvR20 and induction of target gene expression was initiated within 1 min of addition of pyoverdine. FpvR20 was only partially degraded in a mutant lacking the intracellular ClpP protease, resulting in an FpvR20 subfragment (FpvR12) that inhibited σFpvI and σPvdS. The translation inhibitor chloramphenicol did not prevent induction of an σFpvI-dependent gene, showing that degradation of FpvR20 released pre-existing σFpvI in an active form. However, chloramphenicol inhibited induction of σPvdS-dependent genes showing that active σPvdS is not released when FpvR20 is degraded and instead, σPvdS must be synthesized in the absence of FpvR20 to be active. These findings show that sigma factor activation occurs rapidly following addition of the inducing signal in a CSS pathway and requires ClpP protease. Induction of gene expression that can arise from release of active sigma from an antisigma protein but can also require new sigma factor synthesis.
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Affiliation(s)
- Thomas F Bishop
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Lois W Martin
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Iain L Lamont
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
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25
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Edgar RJ, Hampton GE, Garcia GPC, Maher MJ, Perugini MA, Ackerley DF, Lamont IL. Integrated activities of two alternative sigma factors coordinate iron acquisition and uptake by Pseudomonas aeruginosa. Mol Microbiol 2017; 106:891-904. [PMID: 28971540 DOI: 10.1111/mmi.13855] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/27/2017] [Indexed: 11/28/2022]
Abstract
Alternative sigma (σ) factors govern expression of bacterial genes in response to diverse environmental signals. In Pseudomonas aeruginosa σPvdS directs expression of genes for production of a siderophore, pyoverdine, as well as a toxin and a protease. σFpvI directs expression of a receptor for ferripyoverdine import. Expression of the genes encoding σPvdS and σFpvI is iron-regulated and an antisigma protein, FpvR20 , post-translationally controls the activities of the sigma factors in response to the amount of ferripyoverdine present. Here we show that iron represses synthesis of σPvdS to a far greater extent than σFpvI . In contrast ferripyoverdine exerts similar effects on the activities of both sigma factors. Using a combination of in vivo and in vitro assays we show that σFpvI and σPvdS have comparable affinities for, and are equally inhibited by, FpvR20 . Importantly, in the absence of ferripyoverdine the amount of FpvR20 per cell is lower than the amount of σFpvI and σPvdS , allowing basal expression of target genes that is required to activate the signalling pathway when ferripyoverdine is present. This complex interplay of transcriptional and post-translational regulation enables a co-ordinated response to ferripyoverdine but distinct responses to iron.
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Affiliation(s)
- Rebecca J Edgar
- Department of Biochemistry, University of Otago, Dunedin, New Zealand.,School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
| | | | - G Patricia Casas Garcia
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Megan J Maher
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Matthew A Perugini
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - David F Ackerley
- School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
| | - Iain L Lamont
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
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26
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Bastiaansen KC, Civantos C, Bitter W, Llamas MA. New Insights into the Regulation of Cell-Surface Signaling Activity Acquired from a Mutagenesis Screen of the Pseudomonas putida IutY Sigma/Anti-Sigma Factor. Front Microbiol 2017; 8:747. [PMID: 28512454 PMCID: PMC5411451 DOI: 10.3389/fmicb.2017.00747] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 04/11/2017] [Indexed: 01/18/2023] Open
Abstract
Cell-surface signaling (CSS) is a signal transfer system that allows Gram-negative bacteria to detect environmental signals and generate a cytosolic response. These systems are composed of an outer membrane receptor that senses the inducing signal, an extracytoplasmic function sigma factor (σECF) that targets the cytosolic response by modifying gene expression and a cytoplasmic membrane anti-sigma factor that keeps the σECF in an inactive state in the absence of the signal and transduces its presence from the outer membrane to the cytosol. Although CSS systems regulate bacterial processes as crucial as stress response, iron scavenging and virulence, the exact mechanisms that drive CSS are still not completely understood. Binding of the signal to the CSS receptor is known to trigger a signaling cascade that results in the regulated proteolysis of the anti-sigma factor and the activation of the σECF in the cytosol. This study was carried out to generate new insights in the proteolytic activation of CSS σECF. We performed a random mutagenesis screen of the unique IutY protein of Pseudomonas putida, a protein that combines a cytosolic σECF domain and a periplasmic anti-sigma factor domain in a single polypeptide. In response to the presence of an iron carrier, the siderophore aerobactin, in the extracellular medium, IutY is processed by two different proteases, Prc and RseP, which results in the release and activation of the σIutY domain. Our experiments show that all IutY mutant proteins that contain periplasmic residues depend on RseP for activation. In contrast, Prc is only required for mutant variants with a periplasmic domain longer than 50 amino acids, which indicates that the periplasmic region of IutY is trimmed down to ~50 amino acids creating the RseP substrate. Moreover, we have identified several conserved residues in the CSS anti-sigma factor family of which mutation leads to constitutive activation of their cognate σECF. These findings advance our knowledge on how CSS activity is regulated by the consecutive action of two proteases. Elucidation of the exact mechanism behind CSS activation will enable the development of strategies to block CSS in pathogenic bacteria.
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Affiliation(s)
- Karlijn C Bastiaansen
- Department of Environmental Protection, Estación Experimental del Zaidín (CSIC)Granada, Spain.,Section of Molecular Microbiology, Department of Molecular Cell Biology, VU University AmsterdamAmsterdam, Netherlands
| | - Cristina Civantos
- Department of Environmental Protection, Estación Experimental del Zaidín (CSIC)Granada, Spain
| | - Wilbert Bitter
- Section of Molecular Microbiology, Department of Molecular Cell Biology, VU University AmsterdamAmsterdam, Netherlands
| | - María A Llamas
- Department of Environmental Protection, Estación Experimental del Zaidín (CSIC)Granada, Spain
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27
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Abstract
Iron is essential for the survival of most bacteria but presents a significant challenge given its limited bioavailability. Furthermore, the toxicity of iron combined with the need to maintain physiological iron levels within a narrow concentration range requires sophisticated systems to sense, regulate, and transport iron. Most bacteria have evolved mechanisms to chelate and transport ferric iron (Fe3+) via siderophore receptor systems, and pathogenic bacteria have further lowered this barrier by employing mechanisms to utilize the host's hemoproteins. Once internalized, heme is cleaved by both oxidative and nonoxidative mechanisms to release iron. Heme, itself a lipophilic and toxic molecule, presents a significant challenge for transport into the cell. As such, pathogenic bacteria have evolved sophisticated cell surface signaling and transport systems to obtain heme from the host. In this review, we summarize the structure and function of the heme-sensing and transport systems of pathogenic bacteria and the potential of these systems as antimicrobial targets.
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Affiliation(s)
- Weiliang Huang
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201;
| | - Angela Wilks
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201;
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28
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Quesada JM, Otero-Asman JR, Bastiaansen KC, Civantos C, Llamas MA. The Activity of the Pseudomonas aeruginosa Virulence Regulator σ(VreI) Is Modulated by the Anti-σ Factor VreR and the Transcription Factor PhoB. Front Microbiol 2016; 7:1159. [PMID: 27536271 PMCID: PMC4971064 DOI: 10.3389/fmicb.2016.01159] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 07/12/2016] [Indexed: 11/13/2022] Open
Abstract
Gene regulation in bacteria is primarily controlled at the level of transcription initiation by modifying the affinity of the RNA polymerase (RNAP) for the promoter. This control often occurs through the substitution of the RNAP sigma (σ) subunit. Next to the primary σ factor, most bacteria contain a variable number of alternative σ factors of which the extracytoplasmic function group (σECF) is predominant. Pseudomonas aeruginosa contains nineteen σECF, including the virulence regulator σVreI. σVreI is encoded by the vreAIR operon, which also encodes a receptor-like protein (VreA) and an anti-σ factor (VreR). These three proteins form a signal transduction pathway known as PUMA3, which controls expression of P. aeruginosa virulence functions. Expression of the vreAIR operon occurs under inorganic phosphate (Pi) limitation and requires the PhoB transcription factor. Intriguingly, the genes of the σVreI regulon are also expressed in low Pi despite the fact that the σVreI repressor, the anti-σ factor VreR, is also produced in this condition. Here we show that although σVreI is partially active under Pi starvation, maximal transcription of the σVreI regulon genes requires the removal of VreR. This strongly suggests that an extra signal, probably host-derived, is required in vivo for full σVreI activation. Furthermore, we demonstrate that the activity of σVreI is modulated not only by VreR but also by the transcription factor PhoB. Presence of this regulator is an absolute requirement for σVreI to complex the DNA and initiate transcription of the PUMA3 regulon. The potential DNA binding sites of these two proteins, which include a pho box and −10 and −35 elements, are proposed.
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Affiliation(s)
- Jose M Quesada
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas Granada, Spain
| | - Joaquín R Otero-Asman
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas Granada, Spain
| | - Karlijn C Bastiaansen
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones CientíficasGranada, Spain; Section of Molecular Microbiology, Department of Molecular Cell Biology, VU University AmsterdamAmsterdam, Netherlands
| | - Cristina Civantos
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas Granada, Spain
| | - María A Llamas
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas Granada, Spain
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29
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Lee K, Lee KM, Go J, Ryu JC, Ryu JH, Yoon SS. The ferrichrome receptor A as a new target for Pseudomonas aeruginosa virulence attenuation. FEMS Microbiol Lett 2016; 363:fnw104. [PMID: 27190289 DOI: 10.1093/femsle/fnw104] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/14/2016] [Indexed: 01/02/2023] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen, known to develop robust biofilms. Its biofilm development increases when antibiotics are presented at subminimal inhibitory concentrations (MICs) for reasons that remain unclear. In order to identify genes that affect biofilm development under such a sublethal antibiotic stress condition, we screened a transposon (Tn) mutant library of PAO1, a prototype P. aeruginosa strain. Among ∼5000 mutants, a fiuA gene mutant was verified to form very defective biofilms in the presence of sub-MIC carbenicillin. The fiuA gene encodes ferrichrome receptor A, involved in the iron acquisition process. Of note, biofilm formation was not decreased in the ΔpchΔpvd mutant defective in the production of pyochelin and pyoverdine, two well-characterized P. aeruginosa siderophore molecules. Moreover, ΔfiuA, a non-polar fiuA deletion mutant, produced a significantly decreased level of elastase, a major virulence determinant. Mouse airway infection experiments revealed that the mutant expressed significantly less pathogenicity. Our results suggest that the fiuA gene has pleiotropic functions that affect P. aeruginosa biofilm development and virulence. The targeting of FiuA could enable the attenuation of P. aeruginosa virulence and may be suitable for the development of a drug that specifically controls the virulence of this important pathogen.
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Affiliation(s)
- Keehoon Lee
- Department of Microbiology and Immunology, Yonsei University College of Medicine, Seoul, 120-752, Korea Brain Korea 21 PLUS Project for Medical Sciences, Yonsei University College of Medicine, Seoul, 120-752, Korea
| | - Kang-Mu Lee
- Department of Microbiology and Immunology, Yonsei University College of Medicine, Seoul, 120-752, Korea
| | - Junhyeok Go
- Department of Microbiology and Immunology, Yonsei University College of Medicine, Seoul, 120-752, Korea Brain Korea 21 PLUS Project for Medical Sciences, Yonsei University College of Medicine, Seoul, 120-752, Korea
| | - Jae-Chan Ryu
- Brain Korea 21 PLUS Project for Medical Sciences, Yonsei University College of Medicine, Seoul, 120-752, Korea The Research Center for Human Natural Defense System, Yonsei University College of Medicine, Seoul, 120-752, Korea
| | - Ji-Hwan Ryu
- Brain Korea 21 PLUS Project for Medical Sciences, Yonsei University College of Medicine, Seoul, 120-752, Korea The Research Center for Human Natural Defense System, Yonsei University College of Medicine, Seoul, 120-752, Korea
| | - Sang Sun Yoon
- Department of Microbiology and Immunology, Yonsei University College of Medicine, Seoul, 120-752, Korea Brain Korea 21 PLUS Project for Medical Sciences, Yonsei University College of Medicine, Seoul, 120-752, Korea Institute for Immunology and Immunological Diseases, Yonsei University College of Medicine, Seoul, 120-752, Korea
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30
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Jensen JL, Balbo A, Neau DB, Chakravarthy S, Zhao H, Sinha SC, Colbert CL. Mechanistic Implications of the Unique Structural Features and Dimerization of the Cytoplasmic Domain of the Pseudomonas Sigma Regulator, PupR. Biochemistry 2015; 54:5867-77. [PMID: 26313375 PMCID: PMC4701049 DOI: 10.1021/acs.biochem.5b00826] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Gram-negative bacteria tightly regulate intracellular levels of iron, an essential nutrient. To ensure this strict control, some outer membrane TonB-dependent transporters (TBDTs) that are responsible for iron import stimulate their own transcription in response to extracellular binding by an iron-laden siderophore. This process is mediated by an inner membrane sigma regulator protein (an anti-sigma factor) that transduces an unknown periplasmic signal from the TBDT to release an intracellular sigma factor from the inner membrane, which ultimately upregulates TBDT transcription. Here, we use the Pseudomonas putida ferric-pseudobactin BN7/BN8 sigma regulator, PupR, as a model system to understand the molecular mechanism of this conserved class of sigma regulators. We have determined the X-ray crystal structure of the cytoplasmic anti-sigma domain (ASD) of PupR to 2.0 Å. Size exclusion chromatography, small-angle X-ray scattering, and sedimentation velocity analytical ultracentrifugation all indicate that, in contrast to other ASDs, the PupR-ASD exists as a dimer in solution. Mutagenesis of residues at the dimer interface identified from the crystal structure disrupts dimerization and protein stability, as determined by sedimentation velocity analytical ultracentrifugation and thermal denaturation circular dichroism spectroscopy. These combined results suggest that this type of inner membrane sigma regulator may utilize an unusual mechanism to sequester their cognate sigma factors and prevent transcription activation.
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Affiliation(s)
- Jaime L. Jensen
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA
| | - Andrea Balbo
- Biomedical Engineering and Physical Science Shared Resource, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland, 20892, USA
| | - David B. Neau
- Department of Chemistry and Chemical Biology, Cornell University, Northeastern Collaborative Access Team, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Srinivas Chakravarthy
- Bio-CAT, Advanced Photon Source, 9700 South Cass Avenue, 3Bldg. 435B, Argonne, IL 60439, USA
| | - Huaying Zhao
- Dynamics of Macromolecular Assembly Section, Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland, 20892, USA
| | - Sangita C. Sinha
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA
| | - Christopher L. Colbert
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050, USA
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31
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Paget MS. Bacterial Sigma Factors and Anti-Sigma Factors: Structure, Function and Distribution. Biomolecules 2015; 5:1245-65. [PMID: 26131973 PMCID: PMC4598750 DOI: 10.3390/biom5031245] [Citation(s) in RCA: 218] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Revised: 05/20/2015] [Accepted: 06/01/2015] [Indexed: 12/18/2022] Open
Abstract
Sigma factors are multi-domain subunits of bacterial RNA polymerase (RNAP) that play critical roles in transcription initiation, including the recognition and opening of promoters as well as the initial steps in RNA synthesis. This review focuses on the structure and function of the major sigma-70 class that includes the housekeeping sigma factor (Group 1) that directs the bulk of transcription during active growth, and structurally-related alternative sigma factors (Groups 2-4) that control a wide variety of adaptive responses such as morphological development and the management of stress. A recurring theme in sigma factor control is their sequestration by anti-sigma factors that occlude their RNAP-binding determinants. Sigma factors are then released through a wide variety of mechanisms, often involving branched signal transduction pathways that allow the integration of distinct signals. Three major strategies for sigma release are discussed: regulated proteolysis, partner-switching, and direct sensing by the anti-sigma factor.
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Affiliation(s)
- Mark S Paget
- School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK.
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32
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Bastiaansen KC, van Ulsen P, Wijtmans M, Bitter W, Llamas MA. Self-cleavage of the Pseudomonas aeruginosa Cell-surface Signaling Anti-sigma Factor FoxR Occurs through an N-O Acyl Rearrangement. J Biol Chem 2015; 290:12237-46. [PMID: 25809487 DOI: 10.1074/jbc.m115.643098] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Indexed: 11/06/2022] Open
Abstract
The Fox system of Pseudomonas aeruginosa is a cell-surface signaling (CSS) pathway employed by the bacterium to sense and respond to the presence of the heterologous siderophore ferrioxamine in the environment. This regulatory pathway controls the transcription of the foxA ferrioxamine receptor gene through the extracytoplasmic function sigma factor σ(FoxI). In the absence of ferrioxamine, the activity of σ(FoxI) is inhibited by the transmembrane anti-sigma factor FoxR. Upon binding of ferrioxamine by the FoxA receptor, FoxR is processed by a complex proteolytic cascade leading to the release and activation of σ(FoxI). Interestingly, we have recently shown that FoxR undergoes self-cleavage between the periplasmic Gly-191 and Thr-192 residues independent of the perception of ferrioxamine. This autoproteolytic event, which is widespread among CSS anti-sigma factors, produces two distinct domains that interact and function together to transduce the presence of the signal. In this work, we provide evidence that the self-cleavage of FoxR is not an enzyme-dependent process but is induced by an N-O acyl rearrangement. Mutation analysis showed that the nucleophilic side chain of the Thr-192 residue at +1 of the cleavage site is required for an attack on the preceding Gly-191, after which the resulting ester bond is likely hydrolyzed. Because the cleavage site is well preserved and the hydrolysis of periplasmic CSS anti-sigma factors is widely observed, we hypothesize that cleavage via an N-O acyl rearrangement is a conserved feature of these proteins.
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Affiliation(s)
- Karlijn C Bastiaansen
- From the Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada E-18008, Spain and Section of Molecular Microbiology, Department of Molecular Cell Biology and
| | - Peter van Ulsen
- Section of Molecular Microbiology, Department of Molecular Cell Biology and
| | - Maikel Wijtmans
- Division of Medicinal Chemistry, Department of Chemistry and Pharmaceutical Sciences, Vrije Universiteit, 1081 HV Amsterdam, The Netherlands
| | - Wilbert Bitter
- Section of Molecular Microbiology, Department of Molecular Cell Biology and
| | - María A Llamas
- From the Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada E-18008, Spain and
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33
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Bastiaansen KC, Otero-Asman JR, Luirink J, Bitter W, Llamas MA. Processing of cell-surface signalling anti-sigma factors prior to signal recognition is a conserved autoproteolytic mechanism that produces two functional domains. Environ Microbiol 2015; 17:3263-77. [PMID: 25581349 DOI: 10.1111/1462-2920.12776] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Revised: 12/19/2014] [Accepted: 01/06/2015] [Indexed: 02/02/2023]
Abstract
Cell-surface signalling (CSS) enables Gram-negative bacteria to transduce an environmental signal into a cytosolic response. This regulatory cascade involves an outer membrane receptor that transmits the signal to an anti-sigma factor in the cytoplasmic membrane, allowing the activation of an extracytoplasmic function (ECF) sigma factor. Recent studies have demonstrated that RseP-mediated proteolysis of the anti-sigma factors is key to σ(ECF) activation. Using the Pseudomonas aeruginosa FoxR anti-sigma factor, we show here that RseP is responsible for the generation of an N-terminal tail that likely contains pro-sigma activity. Furthermore, it has been reported previously that this anti-sigma factor is processed in two separate domains prior to signal recognition. Here, we demonstrate that this process is common in these types of proteins and that the processing event is probably due to autoproteolytic activity. The resulting domains interact and function together to transduce the CSS signal. However, our results also indicate that this processing event is not essential for activity. In fact, we have identified functional CSS anti-sigma factors that are not cleaved prior to signal perception. Together, our results indicate that CSS regulation can occur through both complete and initially processed anti-sigma factors.
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Affiliation(s)
- Karlijn C Bastiaansen
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain.,Section of Molecular Microbiology, Department of Molecular Cell Biology, VU University, Amsterdam, The Netherlands
| | - Joaquín R Otero-Asman
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Joen Luirink
- Section of Molecular Microbiology, Department of Molecular Cell Biology, VU University, Amsterdam, The Netherlands
| | - Wilbert Bitter
- Section of Molecular Microbiology, Department of Molecular Cell Biology, VU University, Amsterdam, The Netherlands
| | - María A Llamas
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
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34
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Edgar RJ, Xu X, Shirley M, Konings AF, Martin LW, Ackerley DF, Lamont IL. Interactions between an anti-sigma protein and two sigma factors that regulate the pyoverdine signaling pathway in Pseudomonas aeruginosa. BMC Microbiol 2014; 14:287. [PMID: 25433393 PMCID: PMC4256889 DOI: 10.1186/s12866-014-0287-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 11/06/2014] [Indexed: 12/03/2022] Open
Abstract
Background Synthesis and uptake of pyoverdine, the primary siderophore of the opportunistic pathogen Pseudomonas aeruginosa, is dependent on two extra-cytoplasmic function (ECF) sigma factors, FpvI and PvdS. FpvI and PvdS are required for expression of the ferri-pyoverdine receptor gene fpvA and of pyoverdine synthesis genes respectively. In the absence of pyoverdine the anti-sigma factor FpvR that spans the cytoplasmic membrane inhibits the activities of both FpvI and PvdS, despite the two sigma factors having low sequence identity. Results To investigate the interactions of FpvR with FpvI and PvdS, we first used a tandem affinity purification system to demonstrate binding of PvdS by the cytoplasmic region of FpvR in P. aeruginosa at physiological levels. The cytoplasmic region of FpvR bound to and inhibited both FpvI and PvdS when the proteins were co-expressed in Escherichia coli. Each sigma factor was then subjected to error prone PCR and site-directed mutagenesis to identify mutations that increased sigma factor activity in the presence of FpvR. In FpvI, the amino acid changes clustered around conserved region four of the protein and are likely to disrupt interactions with FpvR. Deletion of five amino acids from the C-terminal end of FpvI also disrupted interactions with FpvR. Mutations in PvdS were present in conserved regions two and four. Most of these mutations as well as deletion of thirteen amino acids from the C-terminal end of PvdS increased sigma factor activity independent of whether FpvR was present, suggesting that they increase either the stability of PvdS or its affinity for core RNA polymerase. Conclusions These data show that FpvR binds to PvdS in both P. aeruginosa and E. coli, inhibiting its activity. FpvR also binds to and inhibits FpvI and binding of FpvI is likely to involve conserved region four of the sigma factor protein. Electronic supplementary material The online version of this article (doi:10.1186/s12866-014-0287-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Rebecca J Edgar
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin, New Zealand. .,School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
| | - Xin Xu
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
| | - Matt Shirley
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
| | - Anna F Konings
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
| | - Lois W Martin
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
| | - David F Ackerley
- School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
| | - Iain L Lamont
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
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35
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Llamas MA, Imperi F, Visca P, Lamont IL. Cell-surface signaling inPseudomonas: stress responses, iron transport, and pathogenicity. FEMS Microbiol Rev 2014; 38:569-97. [DOI: 10.1111/1574-6976.12078] [Citation(s) in RCA: 116] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2014] [Revised: 05/20/2014] [Accepted: 05/27/2014] [Indexed: 01/06/2023] Open
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36
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Ye L, Matthijs S, Bodilis J, Hildebrand F, Raes J, Cornelis P. Analysis of the draft genome of Pseudomonas fluorescens ATCC17400 indicates a capacity to take up iron from a wide range of sources, including different exogenous pyoverdines. Biometals 2014; 27:633-44. [PMID: 24756978 DOI: 10.1007/s10534-014-9734-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 04/03/2014] [Indexed: 12/16/2022]
Abstract
All fluorescent pseudomonads (Pseudomonas aeruginosa, P. putida, P. fluorescens, P. syringae and others) are known to produce the high-affinity peptidic yellow-green fluorescent siderophore pyoverdine. These siderophores have peptide chains that are quite diverse and more than 50 pyoverdine structures have been elucidated. In the majority of the cases, a Pseudomonas species is also able to produce a second siderophore of lower affinity for iron. Pseudomonas fluorescens ATCC 17400 has been shown to produce a unique second siderophore, (thio)quinolobactin, which has an antimicrobial activity against the phytopathogenic Oomycete Pythium debaryanum. We show that this strain has the capacity to utilize 16 different pyoverdines, suggesting the presence of several ferripyoverdine receptors. Analysis of the draft genome of P. fluorescens ATCC 17400 confirmed the presence of 55 TonB-dependent receptors, the largest so far for Pseudomonas, among which 15 are predicted to be ferripyoverdine receptors (Fpv). Phylogenetic analysis revealed the presence of two different clades containing ferripyoverdine receptors, with sequences similar to the P. aeruginosa type II FpvA forming a separate cluster. Among the other receptors we confirmed the presence of the QbsI (thio)quinolobactin receptor, an ferri-achromobactin and an ornicorrugatin receptor, several catecholate and four putative heme receptors. Twenty five of the receptors genes were found to be associated with genes encoding extracytoplasmic sigma factors (ECF σ) and transmembrane anti-σ sensors.
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Affiliation(s)
- Lumeng Ye
- Department of Bioengineering Sciences, Research Group Microbiology, VIB Structural Biology, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium
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37
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Maillard AP, Girard E, Ziani W, Petit-Härtlein I, Kahn R, Covès J. The crystal structure of the anti-σ factor CnrY in complex with the σ factor CnrH shows a new structural class of anti-σ factors targeting extracytoplasmic function σ factors. J Mol Biol 2014; 426:2313-27. [PMID: 24727125 DOI: 10.1016/j.jmb.2014.04.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 03/19/2014] [Accepted: 04/03/2014] [Indexed: 11/25/2022]
Abstract
Gene expression in bacteria is regulated at the level of transcription initiation, a process driven by σ factors. The regulation of σ factor activity proceeds from the regulation of their cytoplasmic availability, which relies on specific inhibitory proteins called anti-σ factors. With anti-σ factors regulating their availability according to diverse cues, extracytoplasmic function σ factors (σ(ECF)) form a major signal transduction system in bacteria. Here, structure:function relationships have been characterized in an emerging class of minimal-size transmembrane anti-σ factors, using CnrY from Cupriavidus metallidurans CH34 as a model. This study reports the 1.75-Å-resolution structure of CnrY cytosolic domain in complex with CnrH, its cognate σ(ECF), and identifies a small hydrophobic knob in CnrY as the major determinant of this interaction in vivo. Unsuspected structural similarity with the molecular switch regulating the general stress response in α-proteobacteria unravels a new class of anti-σ factors targeting σ(ECF). Members of this class carry out their function via a 30-residue stretch that displays helical propensity but no canonical structure on its own.
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Affiliation(s)
- Antoine P Maillard
- Université Grenoble Alpes, Commissariat à l'Energie Atomique et aux Energies Alternatives, Centre National de la Recherche Scientifique, and Institut de Biologie Structurale, F-38000 Grenoble, France.
| | - Eric Girard
- Université Grenoble Alpes, Commissariat à l'Energie Atomique et aux Energies Alternatives, Centre National de la Recherche Scientifique, and Institut de Biologie Structurale, F-38000 Grenoble, France
| | - Widade Ziani
- Université Grenoble Alpes, Commissariat à l'Energie Atomique et aux Energies Alternatives, Centre National de la Recherche Scientifique, and Institut de Biologie Structurale, F-38000 Grenoble, France
| | - Isabelle Petit-Härtlein
- Université Grenoble Alpes, Commissariat à l'Energie Atomique et aux Energies Alternatives, Centre National de la Recherche Scientifique, and Institut de Biologie Structurale, F-38000 Grenoble, France
| | - Richard Kahn
- Université Grenoble Alpes, Commissariat à l'Energie Atomique et aux Energies Alternatives, Centre National de la Recherche Scientifique, and Institut de Biologie Structurale, F-38000 Grenoble, France
| | - Jacques Covès
- Université Grenoble Alpes, Commissariat à l'Energie Atomique et aux Energies Alternatives, Centre National de la Recherche Scientifique, and Institut de Biologie Structurale, F-38000 Grenoble, France
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38
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Hay ID, Wang Y, Moradali MF, Rehman ZU, Rehm BHA. Genetics and regulation of bacterial alginate production. Environ Microbiol 2014; 16:2997-3011. [DOI: 10.1111/1462-2920.12389] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2013] [Revised: 12/18/2013] [Accepted: 12/22/2013] [Indexed: 12/31/2022]
Affiliation(s)
- Iain D. Hay
- Institute of Fundamental Sciences; Massey University; Palmerston North 4442 New Zealand
| | - Yajie Wang
- Institute of Fundamental Sciences; Massey University; Palmerston North 4442 New Zealand
| | - Mohammed F. Moradali
- Institute of Fundamental Sciences; Massey University; Palmerston North 4442 New Zealand
| | - Zahid U. Rehman
- Institute of Fundamental Sciences; Massey University; Palmerston North 4442 New Zealand
| | - Bernd H. A. Rehm
- Institute of Fundamental Sciences; Massey University; Palmerston North 4442 New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology; Massey University; Palmerston North 4442 New Zealand
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39
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Bastiaansen KC, Ibañez A, Ramos JL, Bitter W, Llamas MA. The Prc and RseP proteases control bacterial cell-surface signalling activity. Environ Microbiol 2014; 16:2433-43. [PMID: 24373018 DOI: 10.1111/1462-2920.12371] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Revised: 12/09/2013] [Accepted: 12/15/2013] [Indexed: 11/29/2022]
Abstract
Extracytoplasmic function (ECF) sigma factors play a key role in the regulation of vital functions in the bacterial response to the environment. In Gram-negative bacteria, activity of these sigma factors is often controlled by cell-surface signalling (CSS), a regulatory system that also involves an outer membrane receptor and a transmembrane anti-sigma factor. To get more insight into the molecular mechanism behind CSS regulation, we have focused on the unique Iut system of Pseudomonas putida. This system contains a hybrid protein containing both a cytoplasmic ECF sigma domain and a periplasmic anti-sigma domain, apparently leading to a permanent interaction between the sigma and anti-sigma factor. We show that the Iut ECF sigma factor regulates the response to aerobactin under iron deficiency conditions and is activated by a proteolytic pathway that involves the sequential action of two proteases: Prc, which removes the periplasmic anti-sigma domain, and RseP, which subsequently removes the transmembrane domain and thereby generates the ECF active transcriptional form. We furthermore demonstrate the role of these proteases in the regulation of classical CSS systems in which the sigma and anti-sigma factors are two different proteins.
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Affiliation(s)
- Karlijn C Bastiaansen
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain; Section of Molecular Microbiology, Department of Molecular Cell Biology, VU University Amsterdam, Amsterdam, The Netherlands
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Schneider JS, Glickman MS. Function of site-2 proteases in bacteria and bacterial pathogens. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:2808-14. [PMID: 24099002 DOI: 10.1016/j.bbamem.2013.04.019] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Revised: 04/11/2013] [Accepted: 04/15/2013] [Indexed: 01/02/2023]
Abstract
Site-2 proteases (S2Ps) are a class of intramembrane metalloproteases named after the founding member of this protein family, human S2P, which control cholesterol and fatty acid biosynthesis by cleaving Sterol Regulatory Element Binding Proteins which control cholesterol and fatty acid biosynthesis. S2Ps are widely distributed in bacteria and participate in diverse pathways that control such diverse functions as membrane integrity, sporulation, lipid biosynthesis, pheromone production, virulence, and others. The most common signaling mechanism mediated by S2Ps is the coupled degradation of transmembrane anti-Sigma factors to activate ECF Sigma factor regulons. However, additional signaling mechanisms continue to emerge as more prokaryotic S2Ps are characterized, including direct proteolysis of membrane embedded transcription factors and proteolysis of non-transcriptional membrane proteins or membrane protein remnants. In this review we seek to comprehensively review the functions of S2Ps in bacteria and bacterial pathogens and attempt to organize these proteases into conceptual groups that will spur further study. This article is part of a Special Issue entitled: Intramembrane Proteases.
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Affiliation(s)
- Jessica S Schneider
- Immunology Program, Memorial Sloan Kettering Cancer Center, 1275 York Ave., New York, NY 10065, USA; Program in Immunology and Microbial Pathogenesis, Weill Cornell Graduate School of Biomedical Sciences, USA
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Reid DW, Latham R, Lamont IL, Camara M, Roddam LF. Molecular analysis of changes in Pseudomonas aeruginosa load during treatment of a pulmonary exacerbation in cystic fibrosis. J Cyst Fibros 2013; 12:688-99. [PMID: 23706827 DOI: 10.1016/j.jcf.2013.03.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 03/04/2013] [Accepted: 03/12/2013] [Indexed: 01/24/2023]
Abstract
BACKGROUND Intravenous antibiotics for pulmonary exacerbations (PEs) of cystic fibrosis (CF) usually target Pseudomonas aeruginosa. Insights into the CF lung microbiome have questioned this approach. We used RT-qPCR to determine whether intravenous antibiotics reduced P. aeruginosa numbers and whether this correlated with improved lung function. We also investigated antibiotic effects on other common respiratory pathogens in CF. METHODS Sputa were collected from patients when stable and again during a PE. Sputa were expectorated into a RNA preservation buffer for RNA extraction and preparation of cDNA. qPCR was used to enumerate viable P. aeruginosa as well as Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, Burkholderia cepacia complex and Aspergillus fumigatus. RESULTS Fifteen CF patients were followed through 21 PEs. A complete set of serial sputum samples was unavailable for two patients (three separate PEs). P. aeruginosa numbers did not increase immediately prior to a PE, but numbers during intravenous antibiotic treatment were reduced ≥4-log in 6/18 and ≥1-log in 4/18 PEs. In 7/18 PEs, P. aeruginosa numbers changed very little with intravenous antibiotics and one patient demonstrated a ≥2-log increase in P. aeruginosa load. H. influenzae and S. pneumoniae were detected in ten and five PEs respectively, but with antibiotic treatment these bacteria rapidly became undetectable in 6/10 and 4/5 PEs, respectively. There was a negative correlation between P. aeruginosa numbers and FEV1 during stable phase (r(s)=0.75, p<0.05), and reductions in P. aeruginosa load with intravenous antibiotic treatment correlated with improved FEV1 (r(s)=0.52, p<0.05). CONCLUSIONS Exacerbations are not due to increased P. aeruginosa numbers in CF adults. However, lung function improvements correlate with reduced P. aeruginosa burden suggesting that current antibiotic treatment strategies remain appropriate in most patients. Improved understanding of PE characterised by unchanged P. aeruginosa numbers and minimal lung function improvement following treatment may allow better targeted therapies.
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Affiliation(s)
- D W Reid
- Menzies Research Institute Tasmania, Hobart, Tasmania, Australia; Queensland Institute of Medical Research, Brisbane, Queensland, Australia; The Prince Charles Hospital, Brisbane, Queensland, Australia.
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Strisovsky K. Structural and mechanistic principles of intramembrane proteolysis--lessons from rhomboids. FEBS J 2013; 280:1579-603. [PMID: 23432912 DOI: 10.1111/febs.12199] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Revised: 02/11/2013] [Accepted: 02/18/2013] [Indexed: 02/03/2023]
Abstract
Intramembrane proteases cleave membrane proteins in their transmembrane helices to regulate a wide range of biological processes. They catalyse hydrolytic reactions within the hydrophobic environment of lipid membranes where water is normally excluded. How? Do the different classes of intramembrane proteases share any mechanistic principles? In this review these questions will be discussed in view of the crystal structures of prokaryotic members of the three known catalytic types of intramembrane proteases published over the past 7 years. Rhomboids, the intramembrane serine proteases that are the best understood family, will be the initial area of focus, and the principles that have arisen from a number of structural and biochemical studies will be considered. The site-2 metalloprotease and GXGD-type aspartyl protease structures will then be discussed, with parallels drawn and differences highlighted between these enzymes and the rhomboids. Despite the significant advances achieved so far, to obtain a detailed understanding of the mechanism of any intramembrane protease, high-resolution structural information on the substrate-enzyme complex is required. This remains a major challenge for the field.
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Affiliation(s)
- Kvido Strisovsky
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
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Braun V, Hantke K. The Tricky Ways Bacteria Cope with Iron Limitation. IRON UPTAKE IN BACTERIA WITH EMPHASIS ON E. COLI AND PSEUDOMONAS 2013. [DOI: 10.1007/978-94-007-6088-2_2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Regulons of three Pseudomonas syringae pv. tomato DC3000 iron starvation sigma factors. Appl Environ Microbiol 2012; 79:725-7. [PMID: 23124242 DOI: 10.1128/aem.02801-12] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas syringae pv. tomato DC3000 contains genes for 15 sigma factors. The majority are members of the extracytoplasmic function class of sigma factors, including five that belong to the iron starvation subgroup. In this study, we identified the genes controlled by three iron starvation sigma factors. Their regulons are composed of a small number of genes likely to be involved in iron uptake.
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Elfarash A, Wei Q, Cornelis P. The soluble pyocins S2 and S4 from Pseudomonas aeruginosa bind to the same FpvAI receptor. Microbiologyopen 2012; 1:268-75. [PMID: 23170226 PMCID: PMC3496971 DOI: 10.1002/mbo3.27] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Revised: 04/20/2012] [Accepted: 04/24/2012] [Indexed: 11/08/2022] Open
Abstract
Soluble (S-type) pyocins are Pseudomonas aeruginosa bacteriocins that kill nonimmune P. aeruginosa cells by gaining entry via a specific receptor, which, in the case of pyocin S2, is the siderophore pyoverdine receptor FpvAI, and in the case of pyocin S3, FpvAII. The nucleic acid sequence at the positions 4327697-4327359 of P. aeruginosa PAO1 genome was not annotated, but it was predicted to encode the immunity gene of the flanking pyocin S4 gene (PA3866) based on our analysis of the genome sequence. Using RT-PCR, the expression of the immunity gene was detected, confirming the existence of an immunity gene overlapping the S4 pyocin gene. The PA3866 coding for pyocin S4 and the downstream gene coding for the immunity protein were cloned and expressed in Escherichia coli and the His-tagged S4 pyocin was obtained in pure form. Forty-three P. aeruginosa strains were typed via PCR to identify their ferripyoverdine receptor gene (fpvAI-III) and were tested for their sensitivity to pyocin S4. All S4-sensitive strains had the type I ferripyoverdine receptor fpvA gene. Some S4-resistant type I fpvA-positive strains were detected, but all of them had the S4 immunity gene, and, following the deletion of the immunity gene, became S4-sensitive. The fpvAI receptor gene was deleted in a S4-sensitive strain, and, as expected, the mutant became resistant to S4. The N-terminal receptor binding domain (RBD) of pyocin S2, which also uses the FpvAI receptor to enter the cell, was cloned in the pET-15b vector, and expressed in E. coli. When the purified RBD was mixed with pyocin S4 at different ratios, an inhibition of killing was observed, indicating that S2 RBD competes with the pyocin S4 for the binding to the FpvAI receptor. The S2 RBD was also shown to enhance the expression of the pvdA pyoverdine gene, suggesting that it, like pyoverdine, works via the known siderophore-mediated signalization pathway.
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Affiliation(s)
- Ameer Elfarash
- Department of Bioengineering Sciences, Research Group of Microbiology, VIB Department of Structural Biology, Vrije Universiteit Brussel Pleinlaan 2, B-1050, Brussels, Belgium
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