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Krantz BA. Anthrax Toxin: Model System for Studying Protein Translocation. J Mol Biol 2024; 436:168521. [PMID: 38458604 DOI: 10.1016/j.jmb.2024.168521] [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: 11/17/2023] [Revised: 02/08/2024] [Accepted: 03/04/2024] [Indexed: 03/10/2024]
Abstract
Dedicated translocase channels are nanomachines that often, but not always, unfold and translocate proteins through narrow pores across the membrane. Generally, these molecular machines utilize external sources of free energy to drive these reactions, since folded proteins are thermodynamically stable, and once unfolded they contain immense diffusive configurational entropy. To catalyze unfolding and translocate the unfolded state at appreciable timescales, translocase channels often utilize analogous peptide-clamp active sites. Here we describe how anthrax toxin has been used as a biophysical model system to study protein translocation. The tripartite bacterial toxin is composed of an oligomeric translocase channel, protective antigen (PA), and two enzymes, edema factor (EF) and lethal factor (LF), which are translocated by PA into mammalian host cells. Unfolding and translocation are powered by the endosomal proton gradient and are catalyzed by three peptide-clamp sites in the PA channel: the α clamp, the ϕ clamp, and the charge clamp. These clamp sites interact nonspecifically with the chemically complex translocating chain, serve to minimize unfolded state configurational entropy, and work cooperatively to promote translocation. Two models of proton gradient driven translocation have been proposed: (i) an extended-chain Brownian ratchet mechanism and (ii) a proton-driven helix-compression mechanism. These models are not mutually exclusive; instead the extended-chain Brownian ratchet likely operates on β-sheet sequences and the helix-compression mechanism likely operates on α-helical sequences. Finally, we compare and contrast anthrax toxin with other related and unrelated translocase channels.
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Affiliation(s)
- Bryan A Krantz
- Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, 650 W. Baltimore Street, Baltimore, MD 21201, USA.
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2
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Teixeira Nunes M, Retailleau P, Raoux-Barbot D, Comisso M, Missinou AA, Velours C, Plancqueel S, Ladant D, Mechold U, Renault L. Functional and structural insights into the multi-step activation and catalytic mechanism of bacterial ExoY nucleotidyl cyclase toxins bound to actin-profilin. PLoS Pathog 2023; 19:e1011654. [PMID: 37747912 PMCID: PMC10553838 DOI: 10.1371/journal.ppat.1011654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 10/05/2023] [Accepted: 09/01/2023] [Indexed: 09/27/2023] Open
Abstract
ExoY virulence factors are members of a family of bacterial nucleotidyl cyclases (NCs) that are activated by specific eukaryotic cofactors and overproduce cyclic purine and pyrimidine nucleotides in host cells. ExoYs act as actin-activated NC toxins. Here, we explore the Vibrio nigripulchritudo Multifunctional-Autoprocessing Repeats-in-ToXin (MARTX) ExoY effector domain (Vn-ExoY) as a model for ExoY-type members that interact with monomeric (G-actin) instead of filamentous (F-actin) actin. Vn-ExoY exhibits moderate binding affinity to free or profilin-bound G-actin but can capture the G-actin:profilin complex, preventing its spontaneous or VASP- or formin-mediated assembly at F-actin barbed ends in vitro. This mechanism may prolong the activated cofactor-bound state of Vn-ExoY at sites of active actin cytoskeleton remodelling. We present a series of high-resolution crystal structures of nucleotide-free, 3'-deoxy-ATP- or 3'-deoxy-CTP-bound Vn-ExoY, activated by free or profilin-bound G-actin-ATP/-ADP, revealing that the cofactor only partially stabilises the nucleotide-binding pocket (NBP) of NC toxins. Substrate binding induces a large, previously-unidentified, closure of their NBP, confining catalytically important residues and metal cofactors around the substrate, and facilitating the recruitment of two metal ions to tightly coordinate the triphosphate moiety of purine or pyrimidine nucleotide substrates. We validate critical residues for both the purinyl and pyrimidinyl cyclase activity of NC toxins in Vn-ExoY and its distantly-related ExoY from Pseudomonas aeruginosa, which specifically interacts with F-actin. The data conclusively demonstrate that NC toxins employ a similar two-metal-ion mechanism for catalysing the cyclisation of nucleotides of different sizes. These structural insights into the dynamics of the actin-binding interface of actin-activated ExoYs and the multi-step activation of all NC toxins offer new perspectives for the specific inhibition of class II bacterial NC enzymes.
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Affiliation(s)
- Magda Teixeira Nunes
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
| | - Pascal Retailleau
- Université Paris Saclay, CNRS, Institut de Chimie des Substances Naturelles, Gif-sur-Yvette, France
| | - Dorothée Raoux-Barbot
- Institut Pasteur, Université Paris Cité, CNRS UMR 3528, Unité de Biochimie des Interactions macromoléculaires, Département de Biologie Structurale et Chimie, Paris, France
| | - Martine Comisso
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
| | - Anani Amegan Missinou
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
| | - Christophe Velours
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
| | - Stéphane Plancqueel
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
| | - Daniel Ladant
- Institut Pasteur, Université Paris Cité, CNRS UMR 3528, Unité de Biochimie des Interactions macromoléculaires, Département de Biologie Structurale et Chimie, Paris, France
| | - Undine Mechold
- Institut Pasteur, Université Paris Cité, CNRS UMR 3528, Unité de Biochimie des Interactions macromoléculaires, Département de Biologie Structurale et Chimie, Paris, France
| | - Louis Renault
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
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3
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Whole-Transcriptome Analysis Highlights Adenylyl Cyclase Toxins-Derived Modulation of NF-κB and ERK1/2 Pathways in Macrophages. Toxins (Basel) 2023; 15:toxins15020139. [PMID: 36828453 PMCID: PMC9967024 DOI: 10.3390/toxins15020139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 01/28/2023] [Accepted: 02/04/2023] [Indexed: 02/12/2023] Open
Abstract
Edema toxin (ET), one of the main toxic factors of Bacillus anthracis (B. anthracis), is a kind of potent adenylate cyclase (AC). B. anthracis has adapted to resist macrophage microbicidal mechanisms in part by secreting ET. To date, there is limited information on the pathogenic mechanisms used by ET to manipulate macrophage function, especially at the transcriptome level. We used RNA sequencing to study transcriptional changes in RAW264.7 cells treated with ET. We aimed to identify molecular events associated with the establishment of infection and followed changes in cellular proteins. Our results indicate that ET inhibited TNF-α expression in the RAW264.7 mouse macrophage cell line by activating the cAMP/PKA pathway. ET challenge of macrophages induced a differential expression of genes that participate in multiple macrophage effector functions such as cytokine production, cell adhesion, and the inflammatory response. Furthermore, ET influenced the expression of components of the ERK1/2, as well as the NF-αB signaling pathways. We also showed that ET treatments inhibit the phosphorylation of the ERK1/2 protein. ET also attenuated NF-αB subunit p65 phosphorylation and transcriptional activity of NF-αB via the cAMP/PKA pathway in macrophages. Since the observed modulatory effects were characteristic only of the bacterial exotoxin ET, we propose this may be a mechanism used by B. anthracis to manipulate macrophages and establish systemic infection.
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4
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Davi M, Sadi M, Pitard I, Chenal A, Ladant D. A Robust and Sensitive Spectrophotometric Assay for the Enzymatic Activity of Bacterial Adenylate Cyclase Toxins. Toxins (Basel) 2022; 14:toxins14100691. [PMID: 36287960 PMCID: PMC9609896 DOI: 10.3390/toxins14100691] [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: 09/12/2022] [Revised: 09/27/2022] [Accepted: 09/28/2022] [Indexed: 11/06/2022] Open
Abstract
Various bacterial pathogens are producing toxins that target the cyclic Nucleotide Monophosphate (cNMPs) signaling pathways in order to facilitate host colonization. Among them, several are exhibiting potent nucleotidyl cyclase activities that are activated by eukaryotic factors, such as the adenylate cyclase (AC) toxin, CyaA, from Bordetella pertussis or the edema factor, EF, from Bacillus anthracis. The characterization of these toxins frequently requires accurate measurements of their enzymatic activity in vitro, in particular for deciphering their structure-to-function relationships by protein engineering and site-directed mutagenesis. Here we describe a simple and robust in vitro assay for AC activity based on the spectrophotometric detection of cyclic AMP (cAMP) after chromatographic separation on aluminum oxide. This assay can accurately detect down to fmol amounts of B. pertussis CyaA and can even be used in complex media, such as cell extracts. The relative advantages and disadvantages of this assay in comparison with other currently available methods are briefly discussed.
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Affiliation(s)
- Marilyne Davi
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, Institut Pasteur, Université Paris Cité, CNRS UMR 3528, 75015 Paris, France
| | - Mirko Sadi
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, Institut Pasteur, Université Paris Cité, CNRS UMR 3528, 75015 Paris, France
- Université Paris Cité, 75014 Paris, France
| | - Irene Pitard
- Structural Bioinformatic Unit, Department of Structural Biology and Chemistry, Institut Pasteur, Université Paris Cité, CNRS UMR 3528, 75015 Paris, France
- Université Paris Sorbonne, 75231 Paris, France
| | - Alexandre Chenal
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, Institut Pasteur, Université Paris Cité, CNRS UMR 3528, 75015 Paris, France
| | - Daniel Ladant
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, Institut Pasteur, Université Paris Cité, CNRS UMR 3528, 75015 Paris, France
- Correspondence: ; Tel.: +33-1-4568-8400
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5
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Yang NJ, Isensee J, Neel DV, Quadros AU, Zhang HXB, Lauzadis J, Liu SM, Shiers S, Belu A, Palan S, Marlin S, Maignel J, Kennedy-Curran A, Tong VS, Moayeri M, Röderer P, Nitzsche A, Lu M, Pentelute BL, Brüstle O, Tripathi V, Foster KA, Price TJ, Collier RJ, Leppla SH, Puopolo M, Bean BP, Cunha TM, Hucho T, Chiu IM. Anthrax toxins regulate pain signaling and can deliver molecular cargoes into ANTXR2 + DRG sensory neurons. Nat Neurosci 2021; 25:168-179. [PMID: 34931070 DOI: 10.1038/s41593-021-00973-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2020] [Accepted: 11/01/2021] [Indexed: 11/09/2022]
Abstract
Bacterial products can act on neurons to alter signaling and function. In the present study, we found that dorsal root ganglion (DRG) sensory neurons are enriched for ANTXR2, the high-affinity receptor for anthrax toxins. Anthrax toxins are composed of protective antigen (PA), which binds to ANTXR2, and the protein cargoes edema factor (EF) and lethal factor (LF). Intrathecal administration of edema toxin (ET (PA + EF)) targeted DRG neurons and induced analgesia in mice. ET inhibited mechanical and thermal sensation, and pain caused by formalin, carrageenan or nerve injury. Analgesia depended on ANTXR2 expressed by Nav1.8+ or Advillin+ neurons. ET modulated protein kinase A signaling in mouse sensory and human induced pluripotent stem cell-derived sensory neurons, and attenuated spinal cord neurotransmission. We further engineered anthrax toxins to introduce exogenous protein cargoes, including botulinum toxin, into DRG neurons to silence pain. Our study highlights interactions between a bacterial toxin and nociceptors, which may lead to the development of new pain therapeutics.
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Affiliation(s)
- Nicole J Yang
- Department of Immunology, Harvard Medical School, Boston, MA, USA
| | - Jörg Isensee
- Translational Pain Research, Department of Anesthesiology and Intensive Care Medicine, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Dylan V Neel
- Department of Immunology, Harvard Medical School, Boston, MA, USA
| | - Andreza U Quadros
- Center for Research in Inflammatory Diseases, Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | | | - Justas Lauzadis
- Department of Anesthesiology, Stony Brook Medicine, Stony Brook, NY, USA
| | | | - Stephanie Shiers
- Department of Neuroscience, Center for Advanced Pain Studies, University of Texas at Dallas, Richardson, TX, USA
| | - Andreea Belu
- Translational Pain Research, Department of Anesthesiology and Intensive Care Medicine, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | | | | | | | | | - Victoria S Tong
- Department of Immunology, Harvard Medical School, Boston, MA, USA
| | - Mahtab Moayeri
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Pascal Röderer
- Institute of Reconstructive Neurobiology, University of Bonn Medical Faculty and University Hospital Bonn, Bonn, Germany.,Cellomics Unit, LIFE & BRAIN GmbH, Bonn, Germany
| | - Anja Nitzsche
- Institute of Reconstructive Neurobiology, University of Bonn Medical Faculty and University Hospital Bonn, Bonn, Germany.,Cellomics Unit, LIFE & BRAIN GmbH, Bonn, Germany
| | - Mike Lu
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Bradley L Pentelute
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA.,The Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA.,Broad Institute of MIT and Harvard, Cambridge, MA, USA.,Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Oliver Brüstle
- Institute of Reconstructive Neurobiology, University of Bonn Medical Faculty and University Hospital Bonn, Bonn, Germany
| | | | | | - Theodore J Price
- Department of Neuroscience, Center for Advanced Pain Studies, University of Texas at Dallas, Richardson, TX, USA
| | - R John Collier
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
| | - Stephen H Leppla
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Michelino Puopolo
- Department of Anesthesiology, Stony Brook Medicine, Stony Brook, NY, USA
| | - Bruce P Bean
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA
| | - Thiago M Cunha
- Center for Research in Inflammatory Diseases, Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Tim Hucho
- Translational Pain Research, Department of Anesthesiology and Intensive Care Medicine, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Isaac M Chiu
- Department of Immunology, Harvard Medical School, Boston, MA, USA.
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6
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Belyy A, Merino F, Mechold U, Raunser S. Mechanism of actin-dependent activation of nucleotidyl cyclase toxins from bacterial human pathogens. Nat Commun 2021; 12:6628. [PMID: 34785651 PMCID: PMC8595890 DOI: 10.1038/s41467-021-26889-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 10/25/2021] [Indexed: 12/19/2022] Open
Abstract
Bacterial human pathogens secrete initially inactive nucleotidyl cyclases that become potent enzymes by binding to actin inside eukaryotic host cells. The underlying molecular mechanism of this activation is, however, unclear. Here, we report structures of ExoY from Pseudomonas aeruginosa and Vibrio vulnificus bound to their corresponding activators F-actin and profilin-G-actin. The structures reveal that in contrast to the apo-state, two flexible regions become ordered and interact strongly with actin. The specific stabilization of these regions results in an allosteric stabilization of the nucleotide binding pocket and thereby to an activation of the enzyme. Differences in the sequence and conformation of the actin-binding regions are responsible for the selective binding to either F- or G-actin. Other nucleotidyl cyclase toxins that bind to calmodulin rather than actin undergo a similar disordered-to-ordered transition during activation, suggesting that the allosteric activation-by-stabilization mechanism of ExoY is conserved in these enzymes, albeit the different activator.
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Affiliation(s)
- Alexander Belyy
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Otto-Hahn-Str. 11, 44227, Dortmund, Germany
| | - Felipe Merino
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Otto-Hahn-Str. 11, 44227, Dortmund, Germany
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, 72076, Tübingen, Germany
| | - Undine Mechold
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
| | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Otto-Hahn-Str. 11, 44227, Dortmund, Germany.
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A Free-Energy Landscape Analysis of Calmodulin Obtained from an NMR Data-Utilized Multi-Scale Divide-and-Conquer Molecular Dynamics Simulation. Life (Basel) 2021; 11:life11111241. [PMID: 34833117 PMCID: PMC8617919 DOI: 10.3390/life11111241] [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: 09/30/2021] [Revised: 11/08/2021] [Accepted: 11/10/2021] [Indexed: 11/16/2022] Open
Abstract
Calmodulin (CaM) is a multifunctional calcium-binding protein, which regulates a variety of biochemical processes. CaM acts through its conformational changes and complex formation with its target enzymes. CaM consists of two globular domains (N-lobe and C-lobe) linked by an extended linker region. Upon calcium binding, the N-lobe and C-lobe undergo local conformational changes, followed by a major conformational change of the entire CaM to wrap the target enzyme. However, the regulation mechanisms, such as allosteric interactions, which regulate the large structural changes, are still unclear. In order to investigate the series of structural changes, the free-energy landscape of CaM was obtained by multi-scale divide-and-conquer molecular dynamics (MSDC-MD). The resultant free-energy landscape (FEL) shows that the Ca2+ bound CaM (holo-CaM) would take an experimentally famous elongated structure, which can be formed in the early stage of structural change, by breaking the inter-domain interactions. The FEL also shows that important interactions complete the structural change from the elongated structure to the ring-like structure. In addition, the FEL might give a guiding principle to predict mutational sites in CaM. In this study, it was demonstrated that the movement process of macroscopic variables on the FEL may be diffusive to some extent, and then, the MSDC-MD is suitable to the parallel computation.
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8
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Yamada T, Tsuge H. Preparation of Clostridium perfringens binary iota-toxin pore complex for structural analysis using cryo-EM. Methods Enzymol 2021; 649:125-148. [PMID: 33712185 DOI: 10.1016/bs.mie.2021.01.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Iota toxin, a type of A-B toxin produced by Clostridium perfringens, comprises an enzymatic component (Ia) and a membrane-binding component (Ib). The translocation of Ia to the target cell via the pore formed by Ib allows it to function as an ADP-ribosyltransferase that inhibits actin polymerization in the host cell. The structure of Ia-bound Ib-pore has been determined using cryo-electron microscopy (cryo-EM), thereby elucidating the mechanism of the initial Ia translocation; however, open questions regarding Ia translocation still exist. In this chapter, we describe a new method of preparing Ia-bound Ib-pore complex samples for structural analysis at high resolution using cryo-EM. This method is different from previously reported methods for other A-B toxins. Consequently, it produces Ib-pore with two different states with short and long membrane-spanning β-barrel stem. We expect that this method will be useful in functional and structural studies of iota toxin and other binary toxins.
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Affiliation(s)
- Tomohito Yamada
- Faculty of Life Sciences, Kyoto Sangyo University, Kyoto, Japan.
| | - Hideaki Tsuge
- Faculty of Life Sciences, Kyoto Sangyo University, Kyoto, Japan; Institute for Protein Dynamics, Kyoto Sangyo University, Kyoto, Japan; Center for Molecular Research in Infectious Diseases, Kyoto Sangyo University, Kyoto, Japan.
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9
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Zheng Y, Yang C, Zheng X, Guan Q, Yu S. Acrylamide treatment alters the level of Ca 2+ and Ca 2+-related protein kinase in spinal cords of rats. Toxicol Ind Health 2021; 37:113-123. [PMID: 33487136 DOI: 10.1177/0748233720971879] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
This study aimed to analyze the neurological changes induced by acrylamide (ACR) poisoning and their underlying mechanisms within the spinal cords of male adult Wistar rats. The rats were randomly divided into three groups (n = 9 rats per group). ACR was intraperitoneally injected to produce axonopathy according to the daily dosing schedules of 20 or 40 mg/kg/day of ACR for eight continuous weeks (three times per week). During the exposure period, body weights and gait scores were assessed, and the concentration of Ca2+ was calculated in 27 mice. Protein kinase A (PKA), protein kinase C (PKC), cyclin-dependent protein kinase 5 (CDK5), and P35 were assessed by electrophoretic resolution and Western blotting. The contents of 3'-cyclic adenosine monophosphate (cAMP) and calmodulin (CaM) were determined using ELISA kits, and the activities of calcium/calmodulin-dependent protein kinase II (CaMKII), PKA, and PKC were determined using the commercial Signa TECTPKAassay kits. Compared with control rats, treatment with 20 and 40 mg/kg of ACR decreased body weight and increased gait scores at 8 weeks. Intracellular Ca2+ levels increased significantly in treated rats; CaM, PKC, CDK5, and P35 levels were significantly decreased; and PKA and cAMP levels remained unchanged. CaMKII, PKA, and PKC activities increased significantly. The results indicated that ACR can damage neurofilaments by affecting the contents and activities of CaM, CaMKII, PKA, cAMP, PKC, CDK5, and P35, which could result in ACR toxic neuropathy.
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Affiliation(s)
- Yunhe Zheng
- Gansu Provincial Center for Disease Control and Prevention, West Lanzhou, Gansu, People's Republic of China
| | - Chen Yang
- Gansu Provincial Center for Disease Control and Prevention, West Lanzhou, Gansu, People's Republic of China
| | - Xiu'e Zheng
- Shandong food and Drug Administration, SDFDA, Jinan, People's Republic of China
| | - Qiangdong Guan
- School of Public Health, Nanjing Medical University, Jiangning District, Nanjing, People's Republic of China
| | - Sufang Yu
- School of Public Health, 12589Shandong University, Jinan, People's Republic of China
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10
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Pitard I, Monet D, Goossens PL, Blondel A, Malliavin TE. Analyzing In Silico the Relationship Between the Activation of the Edema Factor and Its Interaction With Calmodulin. Front Mol Biosci 2020; 7:586544. [PMID: 33344505 PMCID: PMC7746812 DOI: 10.3389/fmolb.2020.586544] [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: 07/23/2020] [Accepted: 11/02/2020] [Indexed: 11/25/2022] Open
Abstract
Molecular dynamics (MD) simulations have been recorded on the complex between the edema factor (EF) of Bacilllus anthracis and calmodulin (CaM), starting from a structure with the orthosteric inhibitor adefovir bound in the EF catalytic site. The starting structure has been destabilized by alternately suppressing different co-factors, such as adefovir ligand or ions, revealing several long-distance correlations between the conformation of CaM, the geometry of the CaM/EF interface, the enzymatic site and the overall organization of the complex. An allosteric communication between CaM/EF interface and the EF catalytic site, highlighted by these correlations, was confirmed by several bioinformatics approaches from the literature. A network of hydrogen bonds and stacking interactions extending from the helix V of of CaM, and the residues of the switches A, B and C, and connecting to catalytic site residues, is a plausible candidate for the mediation of allosteric communication. The greatest variability in volume between the different MD conditions was also found for cavities present at the EF/CaM interface and in the EF catalytic site. The similarity between the predictions from literature and the volume variability might introduce the volume variability as new descriptor of allostery.
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Affiliation(s)
- Irène Pitard
- Unité de Bioinformatique Structurale, Institut Pasteur and CNRS UMR 3528, Paris, France.,Center de Bioinformatique, Biostatistique et Biologie Intégrative, Institut Pasteur and CNRS USR 3756, Paris, France.,Ecole Doctorale Université Paris Sorbonne, Paris, France
| | - Damien Monet
- Unité de Bioinformatique Structurale, Institut Pasteur and CNRS UMR 3528, Paris, France.,Center de Bioinformatique, Biostatistique et Biologie Intégrative, Institut Pasteur and CNRS USR 3756, Paris, France.,Ecole Doctorale Université Paris Sorbonne, Paris, France
| | | | - Arnaud Blondel
- Unité de Bioinformatique Structurale, Institut Pasteur and CNRS UMR 3528, Paris, France.,Center de Bioinformatique, Biostatistique et Biologie Intégrative, Institut Pasteur and CNRS USR 3756, Paris, France
| | - Thérèse E Malliavin
- Unité de Bioinformatique Structurale, Institut Pasteur and CNRS UMR 3528, Paris, France.,Center de Bioinformatique, Biostatistique et Biologie Intégrative, Institut Pasteur and CNRS USR 3756, Paris, France
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11
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Ni X, Jiang J. Cryo-EM Uncovers Atomic Details for Loading Cell-Killing Enzymes to the Anthrax Toxin Pretranslocation Complex. Structure 2020; 28:871-873. [PMID: 32755568 DOI: 10.1016/j.str.2020.07.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In this issue of Structure, Zhou et al. report the structures of full-length lethal and edema factors, the cytotoxic components of the deadly anthrax toxin, in complex with the toxin's cell binding and delivery module, the protective antigen prechannel, providing an atomic description for the toxin recruitment prior to translocation.
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Affiliation(s)
- Xiaodan Ni
- Laboratory of Membrane Proteins and Structural Biology, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jiansen Jiang
- Laboratory of Membrane Proteins and Structural Biology, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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12
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Cryo-EM structure of the fully-loaded asymmetric anthrax lethal toxin in its heptameric pre-pore state. PLoS Pathog 2020; 16:e1008530. [PMID: 32810181 PMCID: PMC7462287 DOI: 10.1371/journal.ppat.1008530] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Revised: 09/01/2020] [Accepted: 06/27/2020] [Indexed: 12/20/2022] Open
Abstract
Anthrax toxin is the major virulence factor secreted by Bacillus anthracis, causing high mortality in humans and other mammals. It consists of a membrane translocase, known as protective antigen (PA), that catalyzes the unfolding of its cytotoxic substrates lethal factor (LF) and edema factor (EF), followed by translocation into the host cell. Substrate recruitment to the heptameric PA pre-pore and subsequent translocation, however, are not well understood. Here, we report three high-resolution cryo-EM structures of the fully-loaded anthrax lethal toxin in its heptameric pre-pore state, which differ in the position and conformation of LFs. The structures reveal that three LFs interact with the heptameric PA and upon binding change their conformation to form a continuous chain of head-to-tail interactions. As a result of the underlying symmetry mismatch, one LF binding site in PA remains unoccupied. Whereas one LF directly interacts with a part of PA called α-clamp, the others do not interact with this region, indicating an intermediate state between toxin assembly and translocation. Interestingly, the interaction of the N-terminal domain with the α-clamp correlates with a higher flexibility in the C-terminal domain of the protein. Based on our data, we propose a model for toxin assembly, in which the relative position of the N-terminal α-helices in the three LFs determines which factor is translocated first.
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13
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Zhou K, Liu S, Hardenbrook NJ, Cui Y, Krantz BA, Zhou ZH. Atomic Structures of Anthrax Prechannel Bound with Full-Length Lethal and Edema Factors. Structure 2020; 28:879-887.e3. [PMID: 32521227 DOI: 10.1016/j.str.2020.05.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 04/09/2020] [Accepted: 05/18/2020] [Indexed: 12/15/2022]
Abstract
Pathogenesis of anthrax disease involves two cytotoxic enzymes-edema factor (EF) and lethal factor (LF)-which are individually recruited by the protective antigen heptamer (PA7) or octamer (PA8) prechannel and subsequently translocated across channels formed on the endosomal membrane upon exposure to low pH. Here, we report the atomic structures of PA8 prechannel-bound full-length EF and LF. In this pretranslocation state, the N-terminal segment of both factors refolds into an α helix engaged in the α clamp of the prechannel. Recruitment to the PA prechannel exposes an originally buried β strand of both toxins and enables domain organization of EF. Many interactions occur on domain interfaces in both PA prechannel-bound EF and LF, leading to toxin compaction prior to translocation. Our results provide key insights into the molecular mechanisms of translocation-coupled protein unfolding and translocation.
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Affiliation(s)
- Kang Zhou
- California NanoSystems Institute, University of California, Los Angeles, CA 90095, USA
| | - Shiheng Liu
- California NanoSystems Institute, University of California, Los Angeles, CA 90095, USA; Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA 90095, USA
| | - Nathan J Hardenbrook
- Department of Microbial Pathogenesis, University of Maryland, Baltimore, Baltimore, MD 21201, USA
| | - Yanxiang Cui
- California NanoSystems Institute, University of California, Los Angeles, CA 90095, USA
| | - Bryan A Krantz
- Department of Microbial Pathogenesis, University of Maryland, Baltimore, Baltimore, MD 21201, USA.
| | - Z Hong Zhou
- California NanoSystems Institute, University of California, Los Angeles, CA 90095, USA; Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA 90095, USA.
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14
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Hardenbrook NJ, Liu S, Zhou K, Ghosal K, Zhou ZH, Krantz BA. Atomic structures of anthrax toxin protective antigen channels bound to partially unfolded lethal and edema factors. Nat Commun 2020; 11:840. [PMID: 32047164 PMCID: PMC7012834 DOI: 10.1038/s41467-020-14658-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 01/15/2020] [Indexed: 11/09/2022] Open
Abstract
Following assembly, the anthrax protective antigen (PA) forms an oligomeric translocon that unfolds and translocates either its lethal factor (LF) or edema factor (EF) into the host cell. Here, we report the cryo-EM structures of heptameric PA channels with partially unfolded LF and EF at 4.6 and 3.1-Å resolution, respectively. The first α helix and β strand of LF and EF unfold and dock into a deep amphipathic cleft, called the α clamp, which resides at the interface of two PA monomers. The α-clamp-helix interactions exhibit structural plasticity when comparing the structures of lethal and edema toxins. EF undergoes a largescale conformational rearrangement when forming the complex with the channel. A critical loop in the PA binding interface is displaced for about 4 Å, leading to the weakening of the binding interface prior to translocation. These structures provide key insights into the molecular mechanisms of translocation-coupled protein unfolding and translocation.
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Affiliation(s)
- Nathan J Hardenbrook
- Department of Microbial Pathogenesis, University of Maryland, Baltimore, Baltimore, MD, 21201, USA
| | - Shiheng Liu
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA, 90095, USA
- California NanoSystems Institute, University of California, Los Angeles, CA, 90095, USA
| | - Kang Zhou
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA, 90095, USA
- California NanoSystems Institute, University of California, Los Angeles, CA, 90095, USA
| | - Koyel Ghosal
- Department of Microbial Pathogenesis, University of Maryland, Baltimore, Baltimore, MD, 21201, USA
| | - Z Hong Zhou
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA, 90095, USA.
- California NanoSystems Institute, University of California, Los Angeles, CA, 90095, USA.
| | - Bryan A Krantz
- Department of Microbial Pathogenesis, University of Maryland, Baltimore, Baltimore, MD, 21201, USA.
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15
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Mancl JM, Suarez C, Liang WG, Kovar DR, Tang WJ. Pseudomonas aeruginosa exoenzyme Y directly bundles actin filaments. J Biol Chem 2020; 295:3506-3517. [PMID: 32019868 DOI: 10.1074/jbc.ra119.012320] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 01/23/2020] [Indexed: 11/06/2022] Open
Abstract
Pseudomonas aeruginosa uses a type III secretion system (T3SS) to inject cytotoxic effector proteins into host cells. The promiscuous nucleotidyl cyclase, exoenzyme Y (ExoY), is one of the most common effectors found in clinical P. aeruginosa isolates. Recent studies have revealed that the nucleotidyl cyclase activity of ExoY is stimulated by actin filaments (F-actin) and that ExoY alters actin cytoskeleton dynamics in vitro, via an unknown mechanism. The actin cytoskeleton plays an important role in numerous key biological processes and is targeted by many pathogens to gain competitive advantages. We utilized total internal reflection fluorescence microscopy, bulk actin assays, and EM to investigate how ExoY impacts actin dynamics. We found that ExoY can directly bundle actin filaments with high affinity, comparable with eukaryotic F-actin-bundling proteins, such as fimbrin. Of note, ExoY enzymatic activity was not required for F-actin bundling. Bundling is known to require multiple actin-binding sites, yet small-angle X-ray scattering experiments revealed that ExoY is a monomer in solution, and previous data suggested that ExoY possesses only one actin-binding site. We therefore hypothesized that ExoY oligomerizes in response to F-actin binding and have used the ExoY structure to construct a dimer-based structural model for the ExoY-F-actin complex. Subsequent mutational analyses suggested that the ExoY oligomerization interface plays a crucial role in mediating F-actin bundling. Our results indicate that ExoY represents a new class of actin-binding proteins that modulate the actin cytoskeleton both directly, via F-actin bundling, and indirectly, via actin-activated nucleotidyl cyclase activity.
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Affiliation(s)
- Jordan M Mancl
- Ben May Department for Cancer Research, University of Chicago, Chicago, Illinois 60637
| | - Cristian Suarez
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois 60637
| | - Wenguang G Liang
- Ben May Department for Cancer Research, University of Chicago, Chicago, Illinois 60637
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois 60637
| | - Wei-Jen Tang
- Ben May Department for Cancer Research, University of Chicago, Chicago, Illinois 60637.
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16
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Zhang J, Kinch LN, Cong Q, Katsonis P, Lichtarge O, Savojardo C, Babbi G, Martelli PL, Capriotti E, Casadio R, Garg A, Pal D, Weile J, Sun S, Verby M, Roth FP, Grishin NV. Assessing predictions on fitness effects of missense variants in calmodulin. Hum Mutat 2019; 40:1463-1473. [PMID: 31283071 DOI: 10.1002/humu.23857] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 06/26/2019] [Accepted: 06/27/2019] [Indexed: 12/19/2022]
Abstract
This paper reports the evaluation of predictions for the "CALM1" challenge in the fifth round of the Critical Assessment of Genome Interpretation held in 2018. In the challenge, the participants were asked to predict effects on yeast growth caused by missense variants of human calmodulin, a highly conserved protein in eukaryotic cells sensing calcium concentration. The performance of predictors implementing different algorithms and methods is similar. Most predictors are able to identify the deleterious or tolerated variants with modest accuracy, with a baseline predictor based purely on sequence conservation slightly outperforming the submitted predictions. Nevertheless, we think that the accuracy of predictions remains far from satisfactory, and the field awaits substantial improvements. The most poorly predicted variants in this round surround functional CALM1 sites that bind calcium or peptide, which suggests that better incorporation of structural analysis may help improve predictions.
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Affiliation(s)
- Jing Zhang
- Departments of Biophysics and Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Lisa N Kinch
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Qian Cong
- Departments of Biophysics and Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Panagiotis Katsonis
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas
| | - Olivier Lichtarge
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas.,Department of Biochemistry & Molecular Biology, Department of Pharmacology, Computational and Integrative Biomedical Research Center, Baylor College of Medicine, Houston, Texas
| | - Castrense Savojardo
- Biocomputing Group, FABIT/Giorgio Prodi Interdepartmental Center for Cancer Research, University of Bologna, Bologna, Italy
| | - Giulia Babbi
- Biocomputing Group, FABIT/Giorgio Prodi Interdepartmental Center for Cancer Research, University of Bologna, Bologna, Italy
| | - Pier Luigi Martelli
- Biocomputing Group, FABIT/Giorgio Prodi Interdepartmental Center for Cancer Research, University of Bologna, Bologna, Italy
| | - Emidio Capriotti
- Biocomputing Group, FABIT/Giorgio Prodi Interdepartmental Center for Cancer Research, University of Bologna, Bologna, Italy
| | - Rita Casadio
- Biocomputing Group, FABIT/Giorgio Prodi Interdepartmental Center for Cancer Research, University of Bologna, Bologna, Italy
| | - Aditi Garg
- Department of Computational and Data Sciences, Indian Institute of Science, Bangalore, India
| | - Debnath Pal
- Department of Computational and Data Sciences, Indian Institute of Science, Bangalore, India
| | - Jochen Weile
- Lunenfeld-Tanenbaum Research Institute, Toronto, Ontario, Canada.,The Donnelly Centre, University of Toronto, Toronto, Ontario, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Song Sun
- Lunenfeld-Tanenbaum Research Institute, Toronto, Ontario, Canada.,The Donnelly Centre, University of Toronto, Toronto, Ontario, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Marta Verby
- Lunenfeld-Tanenbaum Research Institute, Toronto, Ontario, Canada.,The Donnelly Centre, University of Toronto, Toronto, Ontario, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Frederick P Roth
- Lunenfeld-Tanenbaum Research Institute, Toronto, Ontario, Canada.,The Donnelly Centre, University of Toronto, Toronto, Ontario, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.,Department of Computer Science, University of Toronto, Toronto, Ontario, Canada
| | - Nick V Grishin
- Departments of Biophysics and Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas.,Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas
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17
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Pitard I, Malliavin TE. Structural Biology and Molecular Modeling to Analyze the Entry of Bacterial Toxins and Virulence Factors into Host Cells. Toxins (Basel) 2019; 11:toxins11060369. [PMID: 31238550 PMCID: PMC6628625 DOI: 10.3390/toxins11060369] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 06/17/2019] [Accepted: 06/18/2019] [Indexed: 12/26/2022] Open
Abstract
Understanding the functions and mechanisms of biological systems is an outstanding challenge. One way to overcome it is to combine together several approaches such as molecular modeling and experimental structural biology techniques. Indeed, the interplay between structural and dynamical properties of the system is crucial to unravel the function of molecular machinery’s. In this review, we focus on how molecular simulations along with structural information can aid in interpreting biological data. Here, we examine two different cases: (i) the endosomal translocation toxins (diphtheria, tetanus, botulinum toxins) and (ii) the activation of adenylyl cyclase inside the cytoplasm (edema factor, CyA, ExoY).
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Affiliation(s)
- Irène Pitard
- Unité de Bioinformatique Structurale, Institut Pasteur and CNRS UMR3528, 75015 Paris, France.
- Centre de Bioinformatique, Biostatistique et Biologie Intégrative, Institut Pasteur and CNRS USR3756, 75015 Paris, France.
- Sorbonne Université, Collège Doctoral, Ecole Doctorale Complexité du Vivant, 75005 Paris, France.
| | - Thérèse E Malliavin
- Unité de Bioinformatique Structurale, Institut Pasteur and CNRS UMR3528, 75015 Paris, France.
- Centre de Bioinformatique, Biostatistique et Biologie Intégrative, Institut Pasteur and CNRS USR3756, 75015 Paris, France.
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18
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Belyy A, Santecchia I, Renault L, Bourigault B, Ladant D, Mechold U. The extreme C terminus of the Pseudomonas aeruginosa effector ExoY is crucial for binding to its eukaryotic activator, F-actin. J Biol Chem 2018; 293:19785-19796. [PMID: 30377256 DOI: 10.1074/jbc.ra118.003784] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2018] [Revised: 10/22/2018] [Indexed: 12/25/2022] Open
Abstract
Bacterial nucleotidyl cyclase toxins are potent virulence factors that upon entry into eukaryotic cells are stimulated by endogenous cofactors to catalyze the production of large amounts of 3'5'-cyclic nucleoside monophosphates. The activity of the effector ExoY from Pseudomonas aeruginosa is stimulated by the filamentous form of actin (F-actin). Utilizing yeast phenotype analysis, site-directed mutagenesis, functional biochemical assays, and confocal microscopy, we demonstrate that the last nine amino acids of the C terminus of ExoY are crucial for the interaction with F-actin and, consequently, for ExoY's enzymatic activity in vitro and toxicity in a yeast model. We observed that isolated C-terminal sequences of P. aeruginosa ExoY that had been fused to a carrier protein bind to F-actin and that synthetic peptides corresponding to the extreme ExoY C terminus inhibit ExoY enzymatic activity in vitro and compete with the full-length enzyme for F-actin binding. Interestingly, we noted that various P. aeruginosa isolates of the PA14 family, including highly virulent strains, harbor ExoY variants with a mutation altering the C terminus of this effector. We found that these naturally occurring ExoY variants display drastically reduced enzymatic activity and toxicity. Our findings shed light on the molecular basis of the ExoY-F-actin interaction, revealing that the extreme C terminus of ExoY is critical for binding to F-actin in target cells and that some P. aeruginosa isolates carry C-terminally mutated, low-activity ExoY variants.
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Affiliation(s)
- Alexander Belyy
- From the Institut Pasteur, CNRS UMR 3528, Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie and
| | - Ignacio Santecchia
- Unité Biologie et Génétique de la Paroi Bactérienne, Département de Microbiologie, 75724 Paris cedex 15, France and
| | - Louis Renault
- the Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France
| | - Blandine Bourigault
- the Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France
| | - Daniel Ladant
- From the Institut Pasteur, CNRS UMR 3528, Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie and
| | - Undine Mechold
- From the Institut Pasteur, CNRS UMR 3528, Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie and
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19
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Khanppnavar B, Datta S. Crystal structure and substrate specificity of ExoY, a unique T3SS mediated secreted nucleotidyl cyclase toxin from Pseudomonas aeruginosa. Biochim Biophys Acta Gen Subj 2018; 1862:2090-2103. [PMID: 29859257 DOI: 10.1016/j.bbagen.2018.05.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 05/15/2018] [Accepted: 05/25/2018] [Indexed: 01/03/2023]
Abstract
BACKGROUND The nucleotidyl cyclase toxin ExoY is an important virulence determinant of Pseudomonas aeruginosa that causes severe acute and chronic infections in immune-compromised individuals. Additionally, this unique T3SS effector shows a striking preference for cUMP, a newly identified non-canonical secondary messenger. Thereby, ExoY is also considered as a potential tool to study unexplored cUMP signaling pathways. METHODS The crystal structure of ExoY was determined at 2.2 Å resolutions by in-situ proteolysis assisted crystallization and Rosetta-molecular replacement method. Additionally, isothermal calorimetric (ITC) and molecular dynamic (MD) simulation studies were also carried out to gain molecular insights into its substrate specificity and catalysis. RESULTS AND CONCLUSION ExoY is a partially unfolded protein with higher propensity to form soluble higher-order oligomers. However, with meticulous attempts of removing of disordered regions by proteases, the recalcitrant ExoY could be successfully crystallized. The crystal structure of ExoY revealed similar overall structural fold present in other anthrax toxA family of nucleotidyl cyclases, with two-to-three distinctly conserved regions conferring specificity to eukaryotic binding partner. The in-vitro catalytic preference of ExoY is in the following order: cGMP > cUMP > cAMP > cCMP. The substrate specificity of ExoY mainly depends on its ability to bind NTP in proper geometrical orientations. ExoY also seems to prefer one-metal-ion dependent catalysis than two-metal-ion dependent catalysis. GENERAL SIGNIFICANCE Our results provide much needed structural insight on ExoY, an important virulence determinant of Pseudomonas aeruginosa and an exciting tool to study non-canonical cNMP signaling pathways. ACCESSION NUMBERS The structure factors and coordinate files have been deposited in the Protein Data Bank with accession number 5XNW.
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Affiliation(s)
- Basavraj Khanppnavar
- Department of Structural Biology and Bioinformatics, CSIR-Indian Institute of Chemical Biology (CSIR-IICB), Kolkata, India; Academy of Scientific and Innovative Research (AcSIR), India
| | - Saumen Datta
- Department of Structural Biology and Bioinformatics, CSIR-Indian Institute of Chemical Biology (CSIR-IICB), Kolkata, India; Academy of Scientific and Innovative Research (AcSIR), India.
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20
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Shimoyama H. A structural comparison of ‘real’ and ‘model’ calmodulin clarified allosteric interactions regulating domain motion. J Biomol Struct Dyn 2018; 37:1567-1581. [DOI: 10.1080/07391102.2018.1462730] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Hiromitsu Shimoyama
- School of Pharmacy, Kitasato University, Shirokane 5-9-1, Minato-ku, Tokyo 108-8641, Japan
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21
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Arumugham VB, Ulivieri C, Onnis A, Finetti F, Tonello F, Ladant D, Baldari CT. Compartmentalized Cyclic AMP Production by the Bordetella pertussis and Bacillus anthracis Adenylate Cyclase Toxins Differentially Affects the Immune Synapse in T Lymphocytes. Front Immunol 2018; 9:919. [PMID: 29765373 PMCID: PMC5938339 DOI: 10.3389/fimmu.2018.00919] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 04/13/2018] [Indexed: 01/01/2023] Open
Abstract
A central feature of the immune synapse (IS) is the tight compartmentalization of membrane receptors and signaling mediators that is functional for its ability to coordinate T cell activation. Second messengers centrally implicated in this process, such as Ca2+ and diacyl glycerol, also undergo compartmentalization at the IS. Current evidence suggests a more complex scenario for cyclic AMP (cAMP), which acts both as positive and as negative regulator of T-cell antigen receptor (TCR) signaling and which, as such, must be subjected to a tight spatiotemporal control to allow for signaling at the IS. Here, we have used two bacterial adenylate cyclase toxins that produce cAMP at different subcellular localizations as the result of their distinct routes of cell invasion, namely Bordetella pertussis CyaA and Bacillus anthracis edema toxin (ET), to address the ability of the T cell to confine cAMP to the site of production and to address the impact of compartmentalized cAMP production on IS assembly and function. We show that CyaA, which produces cAMP close to the synaptic membrane, affects IS stability by modulating not only the distribution of LFA-1 and its partners talin and L-plastin, as previously partly reported but also by promoting the sustained synaptic accumulation of the A-kinase adaptor protein ezrin and protein kinase A while suppressing the β-arrestin-mediated recruitment of phosphodiesterase 4B. These effects are dependent on the catalytic activity of the toxin and can be reproduced by treatment with a non-hydrolyzable cAMP analog. Remarkably, none of these effects are elicited by ET, which produces cAMP at a perinuclear localization, despite its ability to suppress TCR signaling and T cell activation through its cAMP-elevating activity. These results show that the IS responds solely to local elevations of cAMP and provide evidence that potent compartmentalization mechanisms are operational in T cells to contain cAMP close to the site of production, even when produced at supraphysiological levels.
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Affiliation(s)
| | | | - Anna Onnis
- Department of Life Sciences, University of Siena, Siena, Italy
| | | | - Fiorella Tonello
- Neuroscience Institute, Italian National Research Council, Padua, Italy
| | - Daniel Ladant
- Department of Structural Biology and Chemistry, Institut Pasteur, Paris, France
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22
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O’Brien DP, Durand D, Voegele A, Hourdel V, Davi M, Chamot-Rooke J, Vachette P, Brier S, Ladant D, Chenal A. Calmodulin fishing with a structurally disordered bait triggers CyaA catalysis. PLoS Biol 2017; 15:e2004486. [PMID: 29287065 PMCID: PMC5764468 DOI: 10.1371/journal.pbio.2004486] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 01/11/2018] [Accepted: 12/07/2017] [Indexed: 11/18/2022] Open
Abstract
Once translocated into the cytosol of target cells, the catalytic domain (AC) of the adenylate cyclase toxin (CyaA), a major virulence factor of Bordetella pertussis, is potently activated by binding calmodulin (CaM) to produce supraphysiological levels of cAMP, inducing cell death. Using a combination of small-angle X-ray scattering (SAXS), hydrogen/deuterium exchange mass spectrometry (HDX-MS), and synchrotron radiation circular dichroism (SR-CD), we show that, in the absence of CaM, AC exhibits significant structural disorder, and a 75-residue-long stretch within AC undergoes a disorder-to-order transition upon CaM binding. Beyond this local folding, CaM binding induces long-range allosteric effects that stabilize the distant catalytic site, whilst preserving catalytic loop flexibility. We propose that the high enzymatic activity of AC is due to a tight balance between the CaM-induced decrease of structural flexibility around the catalytic site and the preservation of catalytic loop flexibility, allowing for fast substrate binding and product release. The CaM-induced dampening of AC conformational disorder is likely relevant to other CaM-activated enzymes. Calmodulin is a widespread and highly conserved protein that interacts with a wide variety of eukaryotic proteins and enzymes, controlling their activities in response to calcium. The adenylate cyclase toxin (CyaA) of Bordetella pertussis, the causative agent of whooping cough, is one such calmodulin target. Once transported across the plasma membrane of eukaryotic cells, the catalytic domain (AC) of CyaA is activated by calmodulin, producing high levels of cAMP, which can induce cell death. We use an integrative structural biology approach combining several biophysical techniques to characterize the structural rearrangements in AC upon calmodulin binding and to elucidate their relationship to CyaA activation. We show that a disordered stretch of 75 amino acid residues in AC serves as a bait for calmodulin capture. Binding induces significant folding within this region, a prerequisite for CyaA activation. Calmodulin binding promotes the stabilization of the distant catalytic site, whilst maintaining its catalytic loop in a flexible and exposed state. Both phenomena contribute to the high enzymatic activity of AC, allowing for fast substrate binding and cAMP release. The calmodulin-induced reduction of AC conformational disorder is likely relevant to other calmodulin-activated enzymes.
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Affiliation(s)
- Darragh P. O’Brien
- Institut Pasteur, UMR CNRS 3528, Chemistry and Structural Biology Department, Paris, France
| | - Dominique Durand
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette cedex, France
- * E-mail: (A.C.); (D.L.); (D.D.); (S.B.)
| | - Alexis Voegele
- Institut Pasteur, UMR CNRS 3528, Chemistry and Structural Biology Department, Paris, France
| | - Véronique Hourdel
- Institut Pasteur, USR CNRS 2000, Chemistry and Structural Biology Department, CITECH, Paris, France
| | - Marilyne Davi
- Institut Pasteur, UMR CNRS 3528, Chemistry and Structural Biology Department, Paris, France
| | - Julia Chamot-Rooke
- Institut Pasteur, USR CNRS 2000, Chemistry and Structural Biology Department, CITECH, Paris, France
| | - Patrice Vachette
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette cedex, France
| | - Sébastien Brier
- Institut Pasteur, USR CNRS 2000, Chemistry and Structural Biology Department, CITECH, Paris, France
- * E-mail: (A.C.); (D.L.); (D.D.); (S.B.)
| | - Daniel Ladant
- Institut Pasteur, UMR CNRS 3528, Chemistry and Structural Biology Department, Paris, France
- * E-mail: (A.C.); (D.L.); (D.D.); (S.B.)
| | - Alexandre Chenal
- Institut Pasteur, UMR CNRS 3528, Chemistry and Structural Biology Department, Paris, France
- * E-mail: (A.C.); (D.L.); (D.D.); (S.B.)
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Villalobo A, Ishida H, Vogel HJ, Berchtold MW. Calmodulin as a protein linker and a regulator of adaptor/scaffold proteins. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1865:507-521. [PMID: 29247668 DOI: 10.1016/j.bbamcr.2017.12.004] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 12/07/2017] [Accepted: 12/08/2017] [Indexed: 01/29/2023]
Abstract
Calmodulin (CaM) is a universal regulator for a huge number of proteins in all eukaryotic cells. Best known is its function as a calcium-dependent modulator of the activity of enzymes, such as protein kinases and phosphatases, as well as other signaling proteins including membrane receptors, channels and structural proteins. However, less well known is the fact that CaM can also function as a Ca2+-dependent adaptor protein, either by bridging between different domains of the same protein or by linking two identical or different target proteins together. These activities are possible due to the fact that CaM contains two independently-folded Ca2+ binding lobes that are able to interact differentially and to some degree separately with targets proteins. In addition, CaM can interact with and regulates several proteins that function exclusively as adaptors. This review provides an overview over our present knowledge concerning the structural and functional aspects of the role of CaM as an adaptor protein and as a regulator of known adaptor/scaffold proteins.
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Affiliation(s)
- Antonio Villalobo
- Department of Cancer Biology, Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Arturo Duperier 4, E-28029 Madrid, Spain.
| | - Hiroaki Ishida
- Department of Biological Sciences, University of Calgary, 2500 University Dr. N.W., Calgary, Alberta T2N 1N4, Canada
| | - Hans J Vogel
- Department of Biological Sciences, University of Calgary, 2500 University Dr. N.W., Calgary, Alberta T2N 1N4, Canada.
| | - Martin W Berchtold
- Department of Biology, University of Copenhagen, 13 Universitetsparken, DK-2100 Copenhagen Ø, Denmark.
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Suffredini DA, Cui X, Xu W, Li Y, Eichacker PQ. The Potential Pathogenic Contributions of Endothelial Barrier and Arterial Contractile Dysfunction to Shock Due to B. anthracis Lethal and Edema Toxins. Toxins (Basel) 2017; 9:toxins9120394. [PMID: 29210983 PMCID: PMC5744114 DOI: 10.3390/toxins9120394] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 11/24/2017] [Accepted: 11/29/2017] [Indexed: 01/22/2023] Open
Abstract
Shock with B. anthracis infection is particularly resistant to conventional cardiovascular support and its mortality rate appears higher than with more common bacterial pathogens. As opposed to many bacteria that lack exotoxins directly depressing hemodynamic function, lethal and edema toxin (LT and ET respectively) both cause shock and likely contribute to the high lethality rate with B. anthracis. Selective inhibition of the toxins is protective in infection models, and administration of either toxin alone in animals produces hypotension with accompanying organ injury and lethality. Shock during infection is typically due to one of two mechanisms: (i) intravascular volume depletion related to disruption of endothelial barrier function; and (ii) extravasation of fluid and/or maladaptive dilation of peripheral resistance arteries. Although some data suggests that LT can produce myocardial dysfunction, growing evidence demonstrates that it may also interfere with endothelial integrity thereby contributing to the extravasation of fluid that helps characterize severe B. anthracis infection. Edema toxin, on the other hand, while known to produce localized tissue edema when injected subcutaneously, has potent vascular relaxant effects that could lead to pathologic arterial dilation. This review will examine recent data supporting a role for these two pathophysiologic mechanisms underlying the shock LT and ET produce. Further research and a better understanding of these mechanisms may lead to improved management of B. anthracis in patients.
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Affiliation(s)
- Dante A Suffredini
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Building 10, Room 2C145, 9000 Rockville Pike, Bethesda, MD 20892, USA.
| | - Xizhong Cui
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Building 10, Room 2C145, 9000 Rockville Pike, Bethesda, MD 20892, USA.
| | - Wanying Xu
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Building 10, Room 2C145, 9000 Rockville Pike, Bethesda, MD 20892, USA.
| | - Yan Li
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Building 10, Room 2C145, 9000 Rockville Pike, Bethesda, MD 20892, USA.
| | - Peter Q Eichacker
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Building 10, Room 2C145, 9000 Rockville Pike, Bethesda, MD 20892, USA.
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Johns CW, Finley NL. Site I Inactivation Impacts Calmodulin Calcium Binding and Activation of Bordetella pertussis Adenylate Cyclase Toxin. Toxins (Basel) 2017; 9:toxins9120389. [PMID: 29189743 PMCID: PMC5744109 DOI: 10.3390/toxins9120389] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 11/26/2017] [Accepted: 11/27/2017] [Indexed: 12/20/2022] Open
Abstract
Site I inactivation of calmodulin (CaM) was used to examine the importance of aspartic acid 22 at position 3 in CaM calcium binding, protein folding, and activation of the Bordetella pertussis adenylate cyclase toxin domain (CyaA-ACD). NMR calcium titration experiments showed that site I in the CaM mutant (D22A) remained largely unperturbed, while sites II, III, and IV exhibited calcium-induced conformational changes similar to wild-type CaM (CaMWt). Circular dichroism analyses revealed that D22A had comparable α-helical content to CaMWt, and only modest differences in α-helical composition were detected between CaMWt-CyaA-ACD and D22A-CyaA-ACD complexes. However, the thermal stability of the D22A-CyaA-ACD complex was reduced, as compared to the CaMWt-CyaA-ACD complex. Moreover, CaM-dependent activity of CyaA-ACD decreased 87% in the presence of D22A. Taken together, our findings provide evidence that D22A engages CyaA-ACD, likely through C-terminal mediated binding, and that site I inactivation exerts functional effects through the modification of stabilizing interactions that occur between N-terminal CaM and CyaA-ACD.
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Affiliation(s)
- Christian W Johns
- Cell, Molecular, and Structural Biology Program, Miami University, Oxford, OH 45056, USA.
| | - Natosha L Finley
- Cell, Molecular, and Structural Biology Program, Miami University, Oxford, OH 45056, USA.
- Department of Microbiology, Miami University, Oxford, OH 45056, USA.
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Anthrax Vaccine Precipitated Induces Edema Toxin-Neutralizing, Edema Factor-Specific Antibodies in Human Recipients. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2017; 24:CVI.00165-17. [PMID: 28877928 DOI: 10.1128/cvi.00165-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Accepted: 08/28/2017] [Indexed: 01/22/2023]
Abstract
Edema toxin (ET), composed of edema factor (EF) and protective antigen (PA), is a virulence factor of Bacillus anthracis that alters host immune cell function and contributes to anthrax disease. Anthrax vaccine precipitated (AVP) contains low but detectable levels of EF and can elicit EF-specific antibodies in human recipients of AVP. Active and passive vaccination of mice with EF can contribute to protection from challenge with Bacillus anthracis spores or ET. This study compared humoral responses to ET in recipients of AVP (n = 33) versus anthrax vaccine adsorbed (AVA; n = 66), matched for number of vaccinations and time postvaccination, and further determined whether EF antibodies elicited by AVP contribute to ET neutralization. AVP induced higher incidence (77.8%) and titer (229.8 ± 58.6) of EF antibodies than AVA (4.2% and 7.8 ± 8.3, respectively), reflecting the reported low but detectable presence of EF in AVP. In contrast, PA IgG levels and ET neutralization measured using a luciferase-based cyclic AMP reporter assay were robust and did not differ between the two vaccine groups. Multiple regression analysis failed to detect an independent contribution of EF antibodies to ET neutralization in AVP recipients; however, EF antibodies purified from AVP sera neutralized ET. Serum samples from at least half of EF IgG-positive AVP recipients bound to nine decapeptides located in EF domains II and III. Although PA antibodies are primarily responsible for ET neutralization in recipients of AVP, increased amounts of an EF component should be investigated for the capacity to enhance next-generation, PA-based vaccines.
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Structure-Function Relationships Underlying the Capacity of Bordetella Adenylate Cyclase Toxin to Disarm Host Phagocytes. Toxins (Basel) 2017; 9:toxins9100300. [PMID: 28946636 PMCID: PMC5666347 DOI: 10.3390/toxins9100300] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 09/19/2017] [Accepted: 09/21/2017] [Indexed: 01/18/2023] Open
Abstract
Bordetellae, pathogenic to mammals, produce an immunomodulatory adenylate cyclase toxin-hemolysin (CyaA, ACT or AC-Hly) that enables them to overcome the innate immune defense of the host. CyaA subverts host phagocytic cells by an orchestrated action of its functional domains, where an extremely catalytically active adenylyl cyclase enzyme is delivered into phagocyte cytosol by a pore-forming repeat-in-toxin (RTX) cytolysin moiety. By targeting sentinel cells expressing the complement receptor 3, known as the CD11b/CD18 (αMβ₂) integrin, CyaA compromises the bactericidal functions of host phagocytes and supports infection of host airways by Bordetellae. Here, we review the state of knowledge on structural and functional aspects of CyaA toxin action, placing particular emphasis on signaling mechanisms by which the toxin-produced 3',5'-cyclic adenosine monophosphate (cAMP) subverts the physiology of phagocytic cells.
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Bacillus anthracis Edema Toxin Increases Fractional Free Water and Sodium Reabsorption in an Isolated Perfused Rat Kidney Model. Infect Immun 2017; 85:IAI.00264-17. [PMID: 28438974 DOI: 10.1128/iai.00264-17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 04/13/2017] [Indexed: 11/20/2022] Open
Abstract
Bacillus anthracis edema toxin (ET) consists of protective antigen (PA), necessary for host cell toxin uptake, and edema factor (EF), the toxic moiety which increases host cell cyclic AMP (cAMP). Since vasopressin stimulates renal water and sodium reabsorption via increased tubular cell cAMP levels, we hypothesized the ET would also do so. To test this hypothesis, we employed an isolated perfused rat kidney model. Kidneys were isolated and perfused with modified Krebs-Henseleit buffer. Perfusate and urine samples were obtained at baseline and every 10 min over 150 min following the addition of challenges with or without treatments to the perfusate. In kidneys perfused under constant flow or constant pressure, compared to PA challenge (n = 14 or 15 kidneys, respectively), ET (13 or 15 kidneys, respectively) progressively increased urine cAMP levels, water and sodium reabsorption, and urine osmolality and decreased urine output (P ≤ 0.04, except for sodium reabsorption under constant pressure [P = 0.17]). In ET-challenged kidneys, compared to placebo treatment, adefovir, an EF inhibitor, decreased urine cAMP levels, water and sodium reabsorption, and urine osmolality and increased urine output, while raxibacumab, a PA-directed monoclonal antibody (MAb), decreased urine cAMP levels, free water reabsorption, and urine osmolality and increased urine output (P ≤ 0.03 except for urine output with raxibacumab [P = 0.17]). Upon immunohistochemistry, aquaporin 2 was concentrated along the apical membrane of tubular cells with ET but not PA, and urine aquaporin 2 levels were higher with ET (5.52 ± 1.06 ng/ml versus 1.51 ± 0.44 ng/ml [means ± standard errors of the means {SEM}; P = 0.0001). Edema toxin has renal effects that could contribute to extravascular fluid collection characterizing anthrax infection clinically.
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The Molecular Basis of Toxins' Interactions with Intracellular Signaling via Discrete Portals. Toxins (Basel) 2017; 9:toxins9030107. [PMID: 28300784 PMCID: PMC5371862 DOI: 10.3390/toxins9030107] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 03/02/2017] [Accepted: 03/04/2017] [Indexed: 12/20/2022] Open
Abstract
An understanding of the molecular mechanisms by which microbial, plant or animal-secreted toxins exert their action provides the most important element for assessment of human health risks and opens new insights into therapies addressing a plethora of pathologies, ranging from neurological disorders to cancer, using toxinomimetic agents. Recently, molecular and cellular biology dissecting tools have provided a wealth of information on the action of these diverse toxins, yet, an integrated framework to explain their selective toxicity is still lacking. In this review, specific examples of different toxins are emphasized to illustrate the fundamental mechanisms of toxicity at different biochemical, molecular and cellular- levels with particular consideration for the nervous system. The target of primary action has been highlighted and operationally classified into 13 sub-categories. Selected examples of toxins were assigned to each target category, denominated as portal, and the modulation of the different portal’s signaling was featured. The first portal encompasses the plasma membrane lipid domains, which give rise to pores when challenged for example with pardaxin, a fish toxin, or is subject to degradation when enzymes of lipid metabolism such as phospholipases A2 (PLA2) or phospholipase C (PLC) act upon it. Several major portals consist of ion channels, pumps, transporters and ligand gated ionotropic receptors which many toxins act on, disturbing the intracellular ion homeostasis. Another group of portals consists of G-protein-coupled and tyrosine kinase receptors that, upon interaction with discrete toxins, alter second messengers towards pathological levels. Lastly, subcellular organelles such as mitochondria, nucleus, protein- and RNA-synthesis machineries, cytoskeletal networks and exocytic vesicles are also portals targeted and deregulated by other diverse group of toxins. A fundamental concept can be drawn from these seemingly different toxins with respect to the site of action and the secondary messengers and signaling cascades they trigger in the host. While the interaction with the initial portal is largely determined by the chemical nature of the toxin, once inside the cell, several ubiquitous second messengers and protein kinases/ phosphatases pathways are impaired, to attain toxicity. Therefore, toxins represent one of the most promising natural molecules for developing novel therapeutics that selectively target the major cellular portals involved in human physiology and diseases.
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Springer TI, Emerson CC, Johns CW, Finley NL. Interaction with adenylate cyclase toxin from Bordetella pertussis affects the metal binding properties of calmodulin. FEBS Open Bio 2016; 7:25-34. [PMID: 28097085 PMCID: PMC5221433 DOI: 10.1002/2211-5463.12138] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 09/27/2016] [Accepted: 09/29/2016] [Indexed: 12/16/2022] Open
Abstract
Adenylate cyclase toxin domain (CyaA‐ACD) is a calmodulin (CaM)‐dependent adenylate cyclase involved in Bordetella pertussis pathogenesis. Calcium (Ca2+) and magnesium (Mg2+) concentrations impact CaM‐dependent CyaA‐ACD activation, but the structural mechanisms remain unclear. In this study, NMR, dynamic light scattering, and native PAGE were used to probe Mg2+‐induced transitions in CaM's conformation in the presence of CyaA‐ACD. Mg2+ binding was localized to sites I and II, while sites III and IV remained Ca2+ loaded when CaM was bound to CyaA‐ACD. 2Mg2+/2Ca2+‐loaded CaM/CyaA‐ACD was elongated, whereas mutation of site I altered global complex conformation. These data suggest that CyaA‐ACD interaction moderates CaM's Ca2+‐ and Mg2+‐binding capabilities, which may contribute to pathobiology.
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Affiliation(s)
| | - Corey C Emerson
- Department of Microbiology Miami University Oxford OH USA; Present address: Department of Pharmacology Cleveland Center for Membrane and Structural Biology Case Western Reserve University Cleveland OH 44106 USA
| | - Christian W Johns
- Cell, Molecular, and Structural Biology Program Miami University Oxford OH USA
| | - Natosha L Finley
- Department of Microbiology Miami University Oxford OH USA; Cell, Molecular, and Structural Biology Program Miami University Oxford OH USA
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Jara GE, Martínez L. Anthrax Edema Factor: An Ion-Adaptive Mechanism of Catalysis with Increased Transition-State Conformational Flexibility. J Phys Chem B 2016; 120:6504-14. [DOI: 10.1021/acs.jpcb.6b02527] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Gabriel E. Jara
- Institute of Chemistry, University of Campinas, Campinas, SP 13083-861, Brazil
| | - Leandro Martínez
- Institute of Chemistry, University of Campinas, Campinas, SP 13083-861, Brazil
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Zhao T, Zhao X, Liu J, Meng Y, Feng Y, Fang T, Zhang J, Yang X, Li J, Xu J, Chen W. Diminished but Not Abolished Effect of Two His351 Mutants of Anthrax Edema Factor in a Murine Model. Toxins (Basel) 2016; 8:35. [PMID: 26848687 PMCID: PMC4773788 DOI: 10.3390/toxins8020035] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 01/08/2016] [Accepted: 01/15/2016] [Indexed: 01/14/2023] Open
Abstract
Edema toxin (ET), which is composed of a potent adenylate cyclase (AC), edema factor (EF), and protective antigen (PA), is one of the major toxicity factors of Bacillus anthracis. In this study, we introduced mutations in full-length EF to generate alanine EF(H351A) and arginine EF(H351R) variants. In vitro activity analysis displayed that the adenylyl cyclase activity of both the mutants was significantly diminished compared with the wild-type EF. When the native and mutant toxins were administered subcutaneously in a mouse footpad edema model, severe acute swelling was evoked by wild-type ET, while the symptoms induced by mutant toxins were very minor. Systemic administration of these EF variants caused non-lethal hepatotoxicity. In addition, EF(H351R) exhibited slightly higher activity in causing more severe edema than EF(H351A). Our findings demonstrate that the toxicity of ET is not abolished by substitution of EF residue His351 by alanine or arginine. These results also indicate the potential of the mouse footpad edema model as a sensitive method for evaluating both ET toxicity and the efficacy of candidate therapeutic agents.
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Affiliation(s)
- Taoran Zhao
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
| | - Xinghui Zhao
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
| | - Ju Liu
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
| | - Yingying Meng
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
| | - Yingying Feng
- Department of Colorectal Surgery, the Second Artillery General Hospital, Beijing 100088, China.
| | - Ting Fang
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
| | - Jinlong Zhang
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
| | - Xiuxu Yang
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
| | - Jianmin Li
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
| | - Junjie Xu
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
| | - Wei Chen
- Laboratory of Vaccine and Antibody Engineering, Beijing Institute of Biotechnology, Beijing 100071, China.
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Molecular assembly of lethal factor enzyme and pre-pore heptameric protective antigen in early stage of translocation. J Mol Model 2015; 22:7. [PMID: 26659402 DOI: 10.1007/s00894-015-2878-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 11/25/2015] [Indexed: 10/22/2022]
Abstract
During intoxication, the anthrax toxin lethal (LF) and edema (EF) factors initially assemble with the protective antigen (PA) on the plasma membrane of cells expressing the membrane-bound surface-exposed anthrax toxin receptor (ATR). This takes place at the physiological pH prior to entering the acidic environment of the endosome. We elucidated the molecular dynamics (MD) behaviors of the three-dimensional structure of the (PA63)7LF3 complex in various conformations and analyzed the dynamical properties of the fully loaded pre-pore complex on the plasma membrane at the physiological pH. The analysis points to the interaction networks of amino acids conserved between PA63 octamer and heptamer, which are not affected during the initial stage of the LFs binding. The simulations show an asymmetrical movement of the complex domains that directly affect LFs conformations. The conformational and structural alterations of the 2β2-2β3 loops of PA subunits are associated with pore formation. The early conformational changes of the loops appear as they peel off from the domain 2 toward domain 4 of each PA subunit. The LFs unfold in 1α1 segments of their N-terminal initiating the early stage of the pre-pore formation. The results indicate instable regions within the complex and provide important clues concerning the detail of fluctuating residues of the LF-PA interface regions at the early steps of toxins translocation.
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Different Roles of N-Terminal and C-Terminal Domains in Calmodulin for Activation of Bacillus anthracis Edema Factor. Toxins (Basel) 2015; 7:2598-614. [PMID: 26184312 PMCID: PMC4516931 DOI: 10.3390/toxins7072598] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 06/29/2015] [Accepted: 07/06/2015] [Indexed: 11/17/2022] Open
Abstract
Bacillus anthracis adenylyl cyclase toxin edema factor (EF) is one component of the anthrax toxin and is essential for establishing anthrax disease. EF activation by the eukaryotic Ca2+-sensor calmodulin (CaM) leads to massive cAMP production resulting in edema. cAMP also inhibits the nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase, thus reducing production of reactive oxygen species (ROS) used for host defense in activated neutrophils and thereby facilitating bacterial growth. Methionine (Met) residues in CaM, important for interactions between CaM and its binding partners, can be oxidized by ROS. We investigated the impact of site-specific oxidation of Met in CaM on EF activation using thirteen CaM-mutants (CaM-mut) with Met to leucine (Leu) substitutions. EF activation shows high resistance to oxidative modifications in CaM. An intact structure in the C-terminal region of oxidized CaM is sufficient for major EF activation despite altered secondary structure in the N-terminal region associated with Met oxidation. The secondary structures of CaM-mut were determined and described in previous studies from our group. Thus, excess cAMP production and the associated impairment of host defence may be afforded even under oxidative conditions in activated neutrophils.
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Effects of 39 Compounds on Calmodulin-Regulated Adenylyl Cyclases AC1 and Bacillus anthracis Edema Factor. PLoS One 2015; 10:e0124017. [PMID: 25946093 PMCID: PMC4422518 DOI: 10.1371/journal.pone.0124017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2014] [Accepted: 03/09/2015] [Indexed: 12/29/2022] Open
Abstract
Adenylyl cyclases (ACs) catalyze the conversion of ATP into the second messenger cAMP. Membranous AC1 (AC1) is involved in processes of memory and learning and in muscle pain. The AC toxin edema factor (EF) of Bacillus anthracis is involved in the development of anthrax. Both ACs are stimulated by the eukaryotic Ca2+-sensor calmodulin (CaM). The CaM-AC interaction could constitute a potential target to enhance or impair the AC activity of AC1 and EF to intervene in above (patho)physiological mechanisms. Thus, we analyzed the impact of 39 compounds including typical CaM-inhibitors, an anticonvulsant, an anticholinergic, antidepressants, antipsychotics and Ca2+-antagonists on CaM-stimulated catalytic activity of AC1 and EF. Compounds were tested at 10 μM, i.e., a concentration that can be reached therapeutically for certain antidepressants and antipsychotics. Calmidazolium chloride decreased CaM-stimulated AC1 activity moderately by about 30%. In contrast, CaM-stimulated EF activity was abrogated by calmidazolium chloride and additionally decreased by chlorpromazine, felodipine, penfluridol and trifluoperazine by about 20–40%. The activity of both ACs was decreased by calmidazolium chloride in the presence and absence of CaM. Thus, CaM-stimulated AC1 activity is more insensitive to inhibition by small molecules than CaM-stimulated EF activity. Inhibition of AC1 and EF by calmidazolium chloride is largely mediated via a CaM-independent allosteric mechanism.
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Steegborn C. Structure, mechanism, and regulation of soluble adenylyl cyclases — similarities and differences to transmembrane adenylyl cyclases. Biochim Biophys Acta Mol Basis Dis 2014; 1842:2535-47. [DOI: 10.1016/j.bbadis.2014.08.012] [Citation(s) in RCA: 142] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Revised: 08/19/2014] [Accepted: 08/26/2014] [Indexed: 12/14/2022]
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Abstract
Real innovations in medicine and science are historic and singular; the stories behind each occurrence are precious. At Molecular Medicine we have established the Anthony Cerami Award in Translational Medicine to document and preserve these histories. The monographs recount the seminal events as told in the voice of the original investigators who provided the crucial early insight. These essays capture the essence of discovery, chronicling the birth of ideas that created new fields of research; and launched trajectories that persisted and ultimately influenced how disease is prevented, diagnosed, and treated. In this volume, the first Cerami Award Monograph, by Carl Nathan, MD, chairman of the Department of Microbiology and Immunology at Weill Cornell Medical College, reflects towering genius and soaring inspiration.
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Affiliation(s)
- Carl Nathan
- Weill Cornell Medical College, New York, New York, United States of America
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38
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Leysath CE, Phillips DD, Crown D, Fattah RJ, Moayeri M, Leppla SH. Anthrax edema factor toxicity is strongly mediated by the N-end rule. PLoS One 2013; 8:e74474. [PMID: 24015319 PMCID: PMC3755998 DOI: 10.1371/journal.pone.0074474] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 07/30/2013] [Indexed: 11/29/2022] Open
Abstract
Anthrax edema factor (EF) is a calmodulin-dependent adenylate cyclase that converts adenosine triphosphate (ATP) into 3’–5’-cyclic adenosine monophosphate (cAMP), contributing to the establishment of Bacillus anthracis infections and the resulting pathophysiology. We show that EF adenylate cyclase toxin activity is strongly mediated by the N-end rule, and thus is dependent on the identity of the N-terminal amino acid. EF variants having different N-terminal residues varied by more than 100-fold in potency in cultured cells and mice. EF variants having unfavorable, destabilizing N-terminal residues showed much greater activity in cells when the E1 ubiquitin ligase was inactivated or when proteasome inhibitors were present. Taken together, these results show that EF is uniquely affected by ubiquitination and/or proteasomal degradation.
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Affiliation(s)
- Clinton E. Leysath
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Damilola D. Phillips
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Devorah Crown
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Rasem J. Fattah
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Mahtab Moayeri
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Stephen H. Leppla
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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Seifert R, Dove S. Inhibitors of Bacillus anthracis edema factor. Pharmacol Ther 2013; 140:200-12. [PMID: 23850654 DOI: 10.1016/j.pharmthera.2013.07.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 06/17/2013] [Indexed: 01/09/2023]
Abstract
Edema factor (EF) is a calmodulin (CaM)-activated adenylyl cyclase (AC) toxin from Bacillus anthracis that contributes to anthrax pathogenesis. Anthrax is an important medical problem, but treatment of B. anthracis infections is still unsatisfying. Thus, selective EF inhibitors could be valuable drugs in the treatment of anthrax infection, most importantly shock. The catalytic site of EF, the EF/CaM interaction site and allosteric sites constitute potential drug targets. To this end, most efforts have been directed towards targeting the catalytic site. A major challenge in the field is to obtain compounds with high selectivity for AC toxins relative to mammalian membranous ACs (mACs). 3'-(N-methyl)anthraniloyl-2'-deoxyadenosine-5'-triphosphate is the most potent EF inhibitor known so far (Ki, 10nM), but selectivity relative to mACs needs to be improved (currently ~5-50-fold, depending on the specific mAC isoform considered). AC toxin inhibitors can be identified in virtual screening studies based on available EF crystal structures and examined in cellular test systems or at the level of purified toxin using classic radioisotopic or non-radioactive fluorescence assays. Binding of certain MANT-nucleotides to AC toxins elicits large direct fluorescence- or fluorescence resonance energy transfer signals upon interaction with CaM, and these signals can be used to identify toxin inhibitors in competition binding studies. Collectively, potent EF inhibitors are available, but before they can be used clinically, selectivity against mACs must be improved. However, several methodological approaches, complementing each other, are now available to direct the development of potent, selective, orally applicable and clinically useful EF inhibitors.
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Affiliation(s)
- Roland Seifert
- Institute of Pharmacology, Medical School of Hannover, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany.
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Mapping the epitopes of a neutralizing antibody fragment directed against the lethal factor of Bacillus anthracis and cross-reacting with the homologous edema factor. PLoS One 2013; 8:e65855. [PMID: 23741517 PMCID: PMC3669279 DOI: 10.1371/journal.pone.0065855] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Accepted: 05/03/2013] [Indexed: 11/19/2022] Open
Abstract
The lethal toxin (LT) of Bacillus anthracis, composed of the protective antigen (PA) and the lethal factor (LF), plays an essential role in anthrax pathogenesis. PA also interacts with the edema factor (EF, 20% identity with LF) to form the edema toxin (ET), which has a lesser role in anthrax pathogenesis. The first recombinant antibody fragment directed against LF was scFv 2LF; it neutralizes LT by blocking the interaction between PA and LF. Here, we report that scFv 2LF cross-reacts with EF and cross-neutralizes ET, and we present an in silico method taking advantage of this cross-reactivity to map the epitope of scFv 2LF on both LF and EF. This method identified five epitope candidates on LF, constituted of a total of 32 residues, which were tested experimentally by mutating the residues to alanine. This combined approach precisely identified the epitope of scFv 2LF on LF as five residues (H229, R230, Q234, L235 and Y236), of which three were missed by the consensus epitope candidate identified by pre-existing in silico methods. The homolog of this epitope on EF (H253, R254, E258, L259 and Y260) was experimentally confirmed to constitute the epitope of scFv 2LF on EF. Other inhibitors, including synthetic molecules, could be used to target these epitopes for therapeutic purposes. The in silico method presented here may be of more general interest.
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41
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Tidow H, Nissen P. Structural diversity of calmodulin binding to its target sites. FEBS J 2013; 280:5551-65. [PMID: 23601118 DOI: 10.1111/febs.12296] [Citation(s) in RCA: 211] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 04/11/2013] [Accepted: 04/16/2013] [Indexed: 11/28/2022]
Abstract
Calmodulin (CaM) is a ubiquitous, highly conserved, eukaryotic protein that binds to and regulates a number of diverse target proteins involved in different functions such as metabolism, muscle contraction, apoptosis, memory, inflammation and the immune response. In this minireview, we analyze the large number of CaM-complex structures deposited in the Protein Data Bank (i.e. crystal and nuclear magnetic resonance structures) to gain insight into the structural diversity of CaM-binding sites and mechanisms, such as those for CaM-activated protein kinases and phosphatases, voltage-gated Ca(2+)-channels and the plasma membrane Ca(2+)-ATPase.
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Affiliation(s)
- Henning Tidow
- Centre for Membrane Pumps in Cells and Disease - PUMPkin, Aarhus University, Denmark; Department of Molecular Biology and Genetics, Aarhus University, Denmark
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Mones L, Tang WJ, Florián J. Empirical valence bond simulations of the chemical mechanism of ATP to cAMP conversion by anthrax edema factor. Biochemistry 2013; 52:2672-82. [PMID: 23480863 DOI: 10.1021/bi400088y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The two-metal catalysis by the adenylyl cyclase domain of the anthrax edema factor toxin was simulated using the empirical valence bond (EVB) quantum mechanical/molecular mechanical approach. These calculations considered the energetics of the nucleophile deprotonation and the formation of a new P-O bond in aqueous solution and in the enzyme-substrate complex present in the crystal structure models of the reactant and product states of the reaction. Our calculations support a reaction pathway that involves metal-assisted transfer of a proton from the nucleophile to the bulk aqueous solution followed by subsequent formation of an unstable pentavalent intermediate that decomposes into cAMP and pyrophosphate (PPi). This pathway involves ligand exchange in the first solvation sphere of the catalytic metal. At 12.9 kcal/mol, the barrier for the last step of the reaction, the cleavage of the P-O bond to PPi, corresponds to the highest point on the free energy profile for this reaction pathway. However, this energy is too close to the value of 11.4 kcal/mol calculated for the barrier of the nucleophilic attack step to reach a definitive conclusion about the rate-limiting step. The calculated reaction mechanism is supported by reasonable agreement between the experimental and calculated catalytic rate constant decrease caused by the mutation of the active site lysine 346 to arginine.
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Affiliation(s)
- Letif Mones
- Department of Chemistry, Loyola University Chicago, Chicago, Illinois 60660, USA
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Wynia-Smith SL, Brown MJ, Chirichella G, Kemalyan G, Krantz BA. Electrostatic ratchet in the protective antigen channel promotes anthrax toxin translocation. J Biol Chem 2012; 287:43753-64. [PMID: 23115233 PMCID: PMC3527960 DOI: 10.1074/jbc.m112.419598] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Central to the power-stroke and Brownian-ratchet mechanisms of protein translocation is the process through which nonequilibrium fluctuations are rectified or ratcheted by the molecular motor to transport substrate proteins along a specific axis. We investigated the ratchet mechanism using anthrax toxin as a model. Anthrax toxin is a tripartite toxin comprised of the protective antigen (PA) component, a homooligomeric transmembrane translocase, which translocates two other enzyme components, lethal factor (LF) and edema factor (EF), into the cytosol of the host cell under the proton motive force (PMF). The PA-binding domains of LF and EF (LFN and EFN) possess identical folds and similar solution stabilities; however, EFN translocates ∼10–200-fold slower than LFN, depending on the electrical potential (Δψ) and chemical potential (ΔpH) compositions of the PMF. From an analysis of LFN/EFN chimera proteins, we identified two 10-residue cassettes comprised of charged sequence that were responsible for the impaired translocation kinetics of EFN. These cassettes have nonspecific electrostatic requirements: one surprisingly prefers acidic residues when driven by either a Δψ or a ΔpH; the second requires basic residues only when driven by a Δψ. Through modeling and experiment, we identified a charged surface in the PA channel responsible for charge selectivity. The charged surface latches the substrate and promotes PMF-driven transport. We propose an electrostatic ratchet in the channel, comprised of opposing rings of charged residues, enforces directionality by interacting with charged cassettes in the substrate, thereby generating forces sufficient to drive unfolding.
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Affiliation(s)
- Sarah L Wynia-Smith
- California Institute for Quantitative Biosciences, University of California, Berkeley, California 94720, USA
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Visschedyk D, Rochon A, Tempel W, Dimov S, Park HW, Merrill AR. Certhrax toxin, an anthrax-related ADP-ribosyltransferase from Bacillus cereus. J Biol Chem 2012; 287:41089-102. [PMID: 22992735 DOI: 10.1074/jbc.m112.412809] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We identified Certhrax, the first anthrax-like mART toxin from the pathogenic G9241 strain of Bacillus cereus. Certhrax shares 31% sequence identity with anthrax lethal factor from Bacillus anthracis; however, we have shown that the toxicity of Certhrax resides in the mART domain, whereas anthrax uses a metalloprotease mechanism. Like anthrax lethal factor, Certhrax was found to require protective antigen for host cell entry. This two-domain enzyme was shown to be 60-fold more toxic to mammalian cells than anthrax lethal factor. Certhrax localizes to distinct regions within mouse RAW264.7 cells by 10 min postinfection and is extranuclear in its cellular location. Substitution of catalytic residues shows that the mART function is responsible for the toxicity, and it binds NAD(+) with high affinity (K(D) = 52.3 ± 12.2 μM). We report the 2.2 Å Certhrax structure, highlighting its structural similarities and differences with anthrax lethal factor. We also determined the crystal structures of two good inhibitors (P6 (K(D) = 1.7 ± 0.2 μM, K(i) = 1.8 ± 0.4 μM) and PJ34 (K(D) = 5.8 ± 2.6 μM, K(i) = 9.6 ± 0.3 μM)) in complex with Certhrax. As with other toxins in this family, the phosphate-nicotinamide loop moves toward the NAD(+) binding site with bound inhibitor. These results indicate that Certhrax may be important in the pathogenesis of B. cereus.
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Affiliation(s)
- Danielle Visschedyk
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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Laine É, Martínez L, Ladant D, Malliavin T, Blondel A. Molecular motions as a drug target: mechanistic simulations of anthrax toxin edema factor function led to the discovery of novel allosteric inhibitors. Toxins (Basel) 2012; 4:580-604. [PMID: 23012649 PMCID: PMC3446745 DOI: 10.3390/toxins4080580] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Revised: 07/04/2012] [Accepted: 07/18/2012] [Indexed: 01/14/2023] Open
Abstract
Edema Factor (EF) is a component of Bacillus anthracis toxin essential for virulence. Its adenylyl cyclase activity is induced by complexation with the ubiquitous eukaryotic cellular protein, calmodulin (CaM). EF and its complexes with CaM, nucleotides and/or ions, have been extensively characterized by X-ray crystallography. Those structural data allowed molecular simulations analysis of various aspects of EF action mechanism, including the delineation of EF and CaM domains through their association energetics, the impact of calcium binding on CaM, and the role of catalytic site ions. Furthermore, a transition path connecting the free inactive form to the CaM-complexed active form of EF was built to model the activation mechanism in an attempt to define an inhibition strategy. The cavities at the surface of EF were determined for each path intermediate to identify potential sites where the binding of a ligand could block activation. A non-catalytic cavity (allosteric) was found to shrink rapidly at early stages of the path and was chosen to perform virtual screening. Amongst 18 compounds selected in silico and tested in an enzymatic assay, 6 thiophen ureidoacid derivatives formed a new family of EF allosteric inhibitors with IC50 as low as 2 micromolars.
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Affiliation(s)
- Élodie Laine
- Laboratoire de Biologie et de Pharmacologie Appliquée, Ecole Normale Supérieure de Cachan, 61, avenue du Président Wilson, 94235 Cachan cedex, France;
| | - Leandro Martínez
- The Molecular Biotechnology Group, Institute of Physics of São Carlos, University of São Paulo, Av. Trabalhador Sãocarlense, 400, 13566-590 São Carlos, SP, Brazil;
| | - Daniel Ladant
- Unité de Biochimie des Interactions Macromoléculaires and CNRS UMR 3528, Département de Biologie Structurale et Chimie, Institut Pasteur, 28, rue du Dr. Roux, 75724 Paris Cedex 15, France;
| | - Thérèse Malliavin
- Unité de Bioinformatique Structurale and CNRS UMR 3528, Département de Biologie Structurale et Chimie, Institut Pasteur, 25, rue du Dr. Roux, 75724 Paris Cedex 15, France;
| | - Arnaud Blondel
- Unité de Bioinformatique Structurale and CNRS UMR 3528, Département de Biologie Structurale et Chimie, Institut Pasteur, 25, rue du Dr. Roux, 75724 Paris Cedex 15, France;
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Structure of androcam supports specialized interactions with myosin VI. Proc Natl Acad Sci U S A 2012; 109:13290-5. [PMID: 22851764 DOI: 10.1073/pnas.1209730109] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Androcam replaces calmodulin as a tissue-specific myosin VI light chain on the actin cones that mediate D. melanogaster spermatid individualization. We show that the androcam structure and its binding to the myosin VI structural (Insert 2) and regulatory (IQ) light chain sites are distinct from those of calmodulin and provide a basis for specialized myosin VI function. The androcam N lobe noncanonically binds a single Ca(2+) and is locked in a "closed" conformation, causing androcam to contact the Insert 2 site with its C lobe only. Androcam replacing calmodulin at Insert 2 will increase myosin VI lever arm flexibility, which may favor the compact monomeric form of myosin VI that functions on the actin cones by facilitating the collapse of the C-terminal region onto the motor domain. The tethered androcam N lobe could stabilize the monomer through contacts with C-terminal portions of the motor or recruit other components to the actin cones. Androcam binds the IQ site at all calcium levels, constitutively mimicking a conformation adopted by calmodulin only at intermediate calcium levels. Thus, androcam replacing calmodulin at IQ will abolish a Ca(2+)-regulated, calmodulin-mediated myosin VI structural change. We propose that the N lobe prevents androcam from interfering with other calmodulin-mediated Ca(2+) signaling events. We discuss how gene duplication and mutations that selectively stabilize one of the many conformations available to calmodulin support the molecular evolution of structurally and functionally distinct calmodulin-like proteins.
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47
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Göttle M, Dove S, Seifert R. Bacillus anthracis edema factor substrate specificity: evidence for new modes of action. Toxins (Basel) 2012; 4:505-35. [PMID: 22852066 PMCID: PMC3407890 DOI: 10.3390/toxins4070505] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Revised: 06/15/2012] [Accepted: 06/27/2012] [Indexed: 12/20/2022] Open
Abstract
Since the isolation of Bacillus anthracis exotoxins in the 1960s, the detrimental activity of edema factor (EF) was considered as adenylyl cyclase activity only. Yet the catalytic site of EF was recently shown to accomplish cyclization of cytidine 5'-triphosphate, uridine 5'-triphosphate and inosine 5'-triphosphate, in addition to adenosine 5'-triphosphate. This review discusses the broad EF substrate specificity and possible implications of intracellular accumulation of cyclic cytidine 3':5'-monophosphate, cyclic uridine 3':5'-monophosphate and cyclic inosine 3':5'-monophosphate on cellular functions vital for host defense. In particular, cAMP-independent mechanisms of action of EF on host cell signaling via protein kinase A, protein kinase G, phosphodiesterases and CNG channels are discussed.
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Affiliation(s)
- Martin Göttle
- Department of Neurology, Emory University School of Medicine, 6302 Woodruff Memorial Research Building, 101 Woodruff Circle, Atlanta, GA 30322, USA
- Author to whom correspondence should be addressed; ; Tel.: +1-404-727-1678; Fax: +1-404-727-3157
| | - Stefan Dove
- Department of Medicinal/Pharmaceutical Chemistry II, University of Regensburg, D-93040 Regensburg, Germany;
| | - Roland Seifert
- Institute of Pharmacology, Medical School of Hannover, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany;
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48
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Xu Q, Göhler AK, Kosfeld A, Carlton D, Chiu HJ, Klock HE, Knuth MW, Miller MD, Elsliger MA, Deacon AM, Godzik A, Lesley SA, Jahreis K, Wilson IA. The structure of Mlc titration factor A (MtfA/YeeI) reveals a prototypical zinc metallopeptidase related to anthrax lethal factor. J Bacteriol 2012; 194:2987-99. [PMID: 22467785 PMCID: PMC3370624 DOI: 10.1128/jb.00038-12] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Accepted: 03/23/2012] [Indexed: 12/25/2022] Open
Abstract
MtfA of Escherichia coli (formerly YeeI) was previously identified as a regulator of the phosphoenolpyruvate (PEP)-dependent:glucose phosphotransferase system. MtfA homolog proteins are highly conserved, especially among beta- and gammaproteobacteria. We determined the crystal structures of the full-length MtfA apoenzyme from Klebsiella pneumoniae and its complex with zinc (holoenzyme) at 2.2 and 1.95 Å, respectively. MtfA contains a conserved H(149)E(150)XXH(153)+E(212)+Y(205) metallopeptidase motif. The presence of zinc in the active site induces significant conformational changes in the region around Tyr205 compared to the conformation of the apoenzyme. Additionally, the zinc-bound MtfA structure is in a self-inhibitory conformation where a region that was disordered in the unliganded structure is now observed in the active site and a nonproductive state of the enzyme is formed. MtfA is related to the catalytic domain of the anthrax lethal factor and the Mop protein involved in the virulence of Vibrio cholerae, with conservation in both overall structure and in the residues around the active site. These results clearly provide support for MtfA as a prototypical zinc metallopeptidase (gluzincin clan).
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Affiliation(s)
- Qingping Xu
- Joint Center for Structural Genomics
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California, USA
| | | | - Anne Kosfeld
- Department of Biology and Chemistry, University of Osnabrück, Osnabrück, Germany
| | - Dennis Carlton
- Joint Center for Structural Genomics
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, California, USA
| | - Hsiu-Ju Chiu
- Joint Center for Structural Genomics
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California, USA
| | - Heath E. Klock
- Joint Center for Structural Genomics
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, California, USA
| | - Mark W. Knuth
- Joint Center for Structural Genomics
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, California, USA
| | - Mitchell D. Miller
- Joint Center for Structural Genomics
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California, USA
| | - Marc-André Elsliger
- Joint Center for Structural Genomics
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, California, USA
| | - Ashley M. Deacon
- Joint Center for Structural Genomics
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California, USA
| | - Adam Godzik
- Joint Center for Structural Genomics
- Program on Bioinformatics and Systems Biology, Sanford-Burnham Medical Research Institute, La Jolla, California, USA
- Center for Research in Biological Systems, University of California, San Diego, La Jolla, California, USA
| | - Scott A. Lesley
- Joint Center for Structural Genomics
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, California, USA
- Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, California, USA
| | - Knut Jahreis
- Department of Biology and Chemistry, University of Osnabrück, Osnabrück, Germany
| | - Ian A. Wilson
- Joint Center for Structural Genomics
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, California, USA
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Beierlein JM, Anderson AC. New developments in vaccines, inhibitors of anthrax toxins, and antibiotic therapeutics for Bacillus anthracis. Curr Med Chem 2012; 18:5083-94. [PMID: 22050756 DOI: 10.2174/092986711797636036] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 09/07/2011] [Accepted: 09/09/2011] [Indexed: 01/28/2023]
Abstract
Bacillus anthracis, the causative agent responsible for anthrax infections, poses a significant biodefense threat. There is a high mortality rate associated with untreated anthrax infections; specifically, inhalation anthrax is a particularly virulent form of infection with mortality rates close to 100%, even with aggressive treatment. Currently, a vaccine is not available to the general public and few antibiotics have been approved by the FDA for the treatment of inhalation anthrax. With the threat of natural or engineered bacterial resistance to antibiotics and the limited population for whom the current drugs are approved, there is a clear need for more effective treatments against this deadly infection. A comprehensive review of current research in drug discovery is presented in this article, including efforts to improve the purity and stability of vaccines, design inhibitors targeting the anthrax toxins, and identify inhibitors of novel enzyme targets. High resolution structural information for the anthrax toxins and several essential metabolic enzymes has played a significant role in aiding the structure-based design of potent and selective antibiotics.
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Affiliation(s)
- J M Beierlein
- Dept. Pharmaceutical Sciences, University of Connecticut, 69 N. Eagleville Rd., Storrs, CT 06269, USA
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50
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Feld GK, Brown MJ, Krantz BA. Ratcheting up protein translocation with anthrax toxin. Protein Sci 2012; 21:606-24. [PMID: 22374876 DOI: 10.1002/pro.2052] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Revised: 02/21/2012] [Accepted: 02/22/2012] [Indexed: 01/09/2023]
Abstract
Energy-consuming nanomachines catalyze the directed movement of biopolymers in the cell. They are found both dissolved in the aqueous cytosol as well as embedded in lipid bilayers. Inquiries into the molecular mechanism of nanomachine-catalyzed biopolymer transport have revealed that these machines are equipped with molecular parts, including adjustable clamps, levers, and adaptors, which interact favorably with substrate polypeptides. Biological nanomachines that catalyze protein transport, known as translocases, often require that their substrate proteins unfold before translocation. An unstructured protein chain is likely entropically challenging to bind, push, or pull in a directional manner, especially in a way that produces an unfolding force. A number of ingenious solutions to this problem are now evident in the anthrax toxin system, a model used to study protein translocation. Here we highlight molecular ratchets and current research on anthrax toxin translocation. A picture is emerging of proton-gradient-driven anthrax toxin translocation, and its associated ratchet mechanism likely applies broadly to other systems. We suggest a cyclical thermodynamic order-to-disorder mechanism (akin to a heat-engine cycle) is central to underlying protein translocation: peptide substrates nonspecifically bind to molecular clamps, which possess adjustable affinities; polypeptide substrates compress into helical structures; these clamps undergo proton-gated switching; and the substrate subsequently expands regaining its unfolded state conformational entropy upon translocation.
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Affiliation(s)
- Geoffrey K Feld
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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