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Topitsch A, Schwede T, Pereira J. Outer membrane β-barrel structure prediction through the lens of AlphaFold2. Proteins 2024; 92:3-14. [PMID: 37465978 DOI: 10.1002/prot.26552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2023] [Revised: 06/26/2023] [Accepted: 07/01/2023] [Indexed: 07/20/2023]
Abstract
Most proteins found in the outer membrane of gram-negative bacteria share a common domain: the transmembrane β-barrel. These outer membrane β-barrels (OMBBs) occur in multiple sizes and different families with a wide range of functions evolved independently by amplification from a pool of homologous ancestral ββ-hairpins. This is part of the reason why predicting their three-dimensional (3D) structure, especially by homology modeling, is a major challenge. Recently, DeepMind's AlphaFold v2 (AF2) became the first structure prediction method to reach close-to-experimental atomic accuracy in CASP even for difficult targets. However, membrane proteins, especially OMBBs, were not abundant during their training, raising the question of how accurate the predictions are for these families. In this study, we assessed the performance of AF2 in the prediction of OMBBs and OMBB-like folds of various topologies using an in-house-developed tool for the analysis of OMBB 3D structures, and barrOs. In agreement with previous studies on other membrane protein classes, our results indicate that AF2 predicts transmembrane β-barrel structures at high accuracy independently of the use of templates, even for novel topologies absent from the training set. These results provide confidence on the models generated by AF2 and open the door to the structural elucidation of novel transmembrane β-barrel topologies identified in high-throughput OMBB annotation studies or designed de novo.
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Affiliation(s)
| | - Torsten Schwede
- Biozentrum, University of Basel, Basel, Switzerland
- SIB Swiss Institute of Bioinformatics, Basel, Switzerland
| | - Joana Pereira
- Biozentrum, University of Basel, Basel, Switzerland
- SIB Swiss Institute of Bioinformatics, Basel, Switzerland
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2
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Corbett V, Hallenbeck P, Rychahou P, Chauhan A. Evolving role of seneca valley virus and its biomarker TEM8/ANTXR1 in cancer therapeutics. Front Mol Biosci 2022; 9:930207. [PMID: 36090051 PMCID: PMC9458967 DOI: 10.3389/fmolb.2022.930207] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 07/20/2022] [Indexed: 11/13/2022] Open
Abstract
Oncolytic viruses have made a significant inroad in cancer drug development. Numerous clinical trials are currently investigating oncolytic viruses both as single agents or in combination with various immunomodulators. Oncolytic viruses (OV) are an integral pillar of immuno-oncology and hold potential for not only delivering durable anti-tumor responses but also converting “cold” tumors to “hot” tumors. In this review we will discuss one such promising oncolytic virus called Seneca Valley Virus (SVV-001) and its therapeutic implications. SVV development has seen seismic evolution over the past decade and now boasts of being the only OV with a practically applicable biomarker for viral tropism. We discuss relevant preclinical and clinical data involving SVV and how bio-selecting for TEM8/ANTXR1, a negative tumor prognosticator can lead to first of its kind biomarker driven oncolytic viral cancer therapy.
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Affiliation(s)
- Virginia Corbett
- Department of Internal Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | | | - Piotr Rychahou
- Department of Surgery, Markey Cancer Center, University of Kentucky, Lexington, KY, United States
| | - Aman Chauhan
- Division of Medical Oncology, Department of Internal Medicine, Markey Cancer Center, University of Kentucky, Lexington, KY, United States
- *Correspondence: Aman Chauhan,
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3
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Scott H, Huang W, Andra K, Mamillapalli S, Gonti S, Day A, Zhang K, Mehzabeen N, Battaile KP, Raju A, Lovell S, Bann JG, Taylor DJ. Structure of the anthrax protective antigen D425A dominant negative mutant reveals a stalled intermediate state of pore maturation. J Mol Biol 2022; 434:167548. [PMID: 35304125 DOI: 10.1016/j.jmb.2022.167548] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 03/01/2022] [Accepted: 03/10/2022] [Indexed: 10/18/2022]
Abstract
The tripartite protein complex produced by anthrax bacteria (Bacillus anthracis) is a member of the AB family of β-barrel pore-forming toxins. The protective antigen (PA) component forms an oligomeric prepore that assembles on the host cell surface and serves as a scaffold for binding of lethal and edema factors. Following endocytosis, the acidic environment of the late endosome triggers a pH-induced conformational rearrangement to promote maturation of the PA prepore to a functional, membrane spanning pore that facilitates delivery of lethal and edema factors to the cytosol of the infected host. Here, we show that the dominant-negative D425A mutant of PA stalls anthrax pore maturation in an intermediate state at acidic pH. Our 2.7 Å cryo-EM structure of the intermediate state reveals structural rearrangements that involve constriction of the oligomeric pore combined with an intramolecular dissociation of the pore-forming module. In addition to defining the early stages of anthrax pore maturation, the structure identifies asymmetric conformational changes in the oligomeric pore that are influenced by the precise configuration of adjacent protomers.
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Affiliation(s)
- Harry Scott
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Wei Huang
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Kiran Andra
- Department of Chemistry, Wichita State University, Wichita, KS 67260, USA
| | | | - Srinivas Gonti
- Department of Chemistry, Wichita State University, Wichita, KS 67260, USA
| | - Alexander Day
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Kaiming Zhang
- Stanford Linear Accelerator Center and the Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Nurjahan Mehzabeen
- Protein Structure Laboratory, University of Kansas, Lawrence, KS 66047, USA
| | - Kevin P Battaile
- IMCA-CAT, APS, Argonne National Laboratory, 9700 South Cass Avenue, Building 435A, Argonne, IL 60439, USA
| | - Anjali Raju
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Scott Lovell
- Protein Structure Laboratory, University of Kansas, Lawrence, KS 66047, USA
| | - James G Bann
- Department of Chemistry, Wichita State University, Wichita, KS 67260, USA.
| | - Derek J Taylor
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106, USA; Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106, USA.
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4
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Usha SP, Manoharan H, Deshmukh R, Álvarez-Diduk R, Calucho E, Sai VVR, Merkoçi A. Attomolar analyte sensing techniques (AttoSens): a review on a decade of progress on chemical and biosensing nanoplatforms. Chem Soc Rev 2021; 50:13012-13089. [PMID: 34673860 DOI: 10.1039/d1cs00137j] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Detecting the ultra-low abundance of analytes in real-life samples, such as biological fluids, water, soil, and food, requires the design and development of high-performance biosensing modalities. The breakthrough efforts from the scientific community have led to the realization of sensing technologies that measure the analyte's ultra-trace level, with relevant sensitivity, selectivity, response time, and sampling efficiency, referred to as Attomolar Analyte Sensing Techniques (AttoSens) in this review. In an AttoSens platform, 1 aM detection corresponds to the quantification of 60 target analyte molecules in 100 μL of sample volume. Herein, we review the approaches listed for various sensor probe design, and their sensing strategies that paved the way for the detection of attomolar (aM: 10-18 M) concentration of analytes. A summary of the technological advances made by the diverse AttoSens trends from the past decade is presented.
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Affiliation(s)
- Sruthi Prasood Usha
- Biomedical Engineering, Department of Applied Mechanics, Indian Institute of Technology Madras (IITM), India.
| | - Hariharan Manoharan
- Biomedical Engineering, Department of Applied Mechanics, Indian Institute of Technology Madras (IITM), India.
| | - Rehan Deshmukh
- Biomedical Engineering, Department of Applied Mechanics, Indian Institute of Technology Madras (IITM), India.
| | - Ruslan Álvarez-Diduk
- Nanobioelectronics & Biosensors Group, Institut Català de Nanociència i Nanotecnologia (ICN2), Campus UAB, Barcelona, Spain.
| | - Enric Calucho
- Nanobioelectronics & Biosensors Group, Institut Català de Nanociència i Nanotecnologia (ICN2), Campus UAB, Barcelona, Spain.
| | - V V R Sai
- Biomedical Engineering, Department of Applied Mechanics, Indian Institute of Technology Madras (IITM), India.
| | - Arben Merkoçi
- Nanobioelectronics & Biosensors Group, Institut Català de Nanociència i Nanotecnologia (ICN2), Campus UAB, Barcelona, Spain. .,ICREA, Institució Catalana de Recercai Estudis Avançats, Barcelona, Spain
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5
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Lucas R, Hadizamani Y, Gonzales J, Gorshkov B, Bodmer T, Berthiaume Y, Moehrlen U, Lode H, Huwer H, Hudel M, Mraheil MA, Toque HAF, Chakraborty T, Hamacher J. Impact of Bacterial Toxins in the Lungs. Toxins (Basel) 2020; 12:toxins12040223. [PMID: 32252376 PMCID: PMC7232160 DOI: 10.3390/toxins12040223] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 03/30/2020] [Accepted: 03/31/2020] [Indexed: 12/13/2022] Open
Abstract
Bacterial toxins play a key role in the pathogenesis of lung disease. Based on their structural and functional properties, they employ various strategies to modulate lung barrier function and to impair host defense in order to promote infection. Although in general, these toxins target common cellular signaling pathways and host compartments, toxin- and cell-specific effects have also been reported. Toxins can affect resident pulmonary cells involved in alveolar fluid clearance (AFC) and barrier function through impairing vectorial Na+ transport and through cytoskeletal collapse, as such, destroying cell-cell adhesions. The resulting loss of alveolar-capillary barrier integrity and fluid clearance capacity will induce capillary leak and foster edema formation, which will in turn impair gas exchange and endanger the survival of the host. Toxins modulate or neutralize protective host cell mechanisms of both the innate and adaptive immunity response during chronic infection. In particular, toxins can either recruit or kill central players of the lung's innate immune responses to pathogenic attacks, i.e., alveolar macrophages (AMs) and neutrophils. Pulmonary disorders resulting from these toxin actions include, e.g., acute lung injury (ALI), the acute respiratory syndrome (ARDS), and severe pneumonia. When acute infection converts to persistence, i.e., colonization and chronic infection, lung diseases, such as bronchitis, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF) can arise. The aim of this review is to discuss the impact of bacterial toxins in the lungs and the resulting outcomes for pathogenesis, their roles in promoting bacterial dissemination, and bacterial survival in disease progression.
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Affiliation(s)
- Rudolf Lucas
- Pharmacology and Toxicology, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA;
- Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA;
- Department of Medicine and Division of Pulmonary Critical Care Medicine, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA;
- Correspondence: (R.L.); (J.H.); Tel.: +41-31-300-35-00 (J.H.)
| | - Yalda Hadizamani
- Lungen-und Atmungsstiftung, Bern, 3012 Bern, Switzerland;
- Pneumology, Clinic for General Internal Medicine, Lindenhofspital Bern, 3012 Bern, Switzerland
| | - Joyce Gonzales
- Department of Medicine and Division of Pulmonary Critical Care Medicine, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA;
| | - Boris Gorshkov
- Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA;
| | - Thomas Bodmer
- Labormedizinisches Zentrum Dr. Risch, Waldeggstr. 37 CH-3097 Liebefeld, Switzerland;
| | - Yves Berthiaume
- Department of Medicine, Faculty of Medicine, Université de Montréal, Montréal, QC H3T 1J4, Canada;
| | - Ueli Moehrlen
- Pediatric Surgery, University Children’s Hospital, Zürich, Steinwiesstrasse 75, CH-8032 Zürch, Switzerland;
| | - Hartmut Lode
- Insitut für klinische Pharmakologie, Charité, Universitätsklinikum Berlin, Reichsstrasse 2, D-14052 Berlin, Germany;
| | - Hanno Huwer
- Department of Cardiothoracic Surgery, Voelklingen Heart Center, 66333 Voelklingen/Saar, Germany;
| | - Martina Hudel
- Justus-Liebig-University, Biomedical Research Centre Seltersberg, Schubertstr. 81, 35392 Giessen, Germany; (M.H.); (M.A.M.); (T.C.)
| | - Mobarak Abu Mraheil
- Justus-Liebig-University, Biomedical Research Centre Seltersberg, Schubertstr. 81, 35392 Giessen, Germany; (M.H.); (M.A.M.); (T.C.)
| | - Haroldo Alfredo Flores Toque
- Pharmacology and Toxicology, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA;
- Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA;
| | - Trinad Chakraborty
- Justus-Liebig-University, Biomedical Research Centre Seltersberg, Schubertstr. 81, 35392 Giessen, Germany; (M.H.); (M.A.M.); (T.C.)
| | - Jürg Hamacher
- Lungen-und Atmungsstiftung, Bern, 3012 Bern, Switzerland;
- Pneumology, Clinic for General Internal Medicine, Lindenhofspital Bern, 3012 Bern, Switzerland
- Medical Clinic V-Pneumology, Allergology, Intensive Care Medicine and Environmental Medicine, Faculty of Medicine, Saarland University, University Medical Centre of the Saarland, D-66421 Homburg, Germany
- Institute for Clinical & Experimental Surgery, Faculty of Medicine, Saarland University, D-66421 Homburg, Germany
- Correspondence: (R.L.); (J.H.); Tel.: +41-31-300-35-00 (J.H.)
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Kondakova OA, Nikitin NA, Evtushenko EA, Ryabchevskaya EM, Atabekov JG, Karpova OV. Vaccines against anthrax based on recombinant protective antigen: problems and solutions. Expert Rev Vaccines 2019; 18:813-828. [PMID: 31298973 DOI: 10.1080/14760584.2019.1643242] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Introduction: Anthrax is a dangerous bio-terror agent because Bacillus anthracis spores are highly resilient and can be easily aerosolized and disseminated. There is a threat of deliberate use of anthrax spores aerosol that could lead to serious fatal diseases outbreaks. Existing control measures against inhalation form of the disease are limited. All of this has provided an impetus to the development of new generation vaccines. Areas сovered: This review is devoted to challenges and achievements in the design of vaccines based on the anthrax recombinant protective antigen (rPA). Scientific databases have been searched, focusing on causes of PA instability and solutions to this problem, including new approaches of rPA expression, novel rPA-based vaccines formulations as well as the simultaneous usage of PA with other anthrax antigens. Expert opinion: PA is a central anthrax toxin component, playing a key role in the defense against encapsulated and unencapsulated strains. Subunit rPA-based vaccines have a good safety and protective profile. However, there are problems of PA instability that are greatly enhanced when using aluminum adjuvants. New adjuvant compositions, dry formulations and resistant to proteolysis and deamidation mutant PA forms can help to handle this issue. Devising a modern anthrax vaccine requires huge efforts.
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Affiliation(s)
- Olga A Kondakova
- a Department of Virology, Faculty of Biology, Lomonosov Moscow State University , Moscow , Russian Federation
| | - Nikolai A Nikitin
- a Department of Virology, Faculty of Biology, Lomonosov Moscow State University , Moscow , Russian Federation
| | - Ekaterina A Evtushenko
- a Department of Virology, Faculty of Biology, Lomonosov Moscow State University , Moscow , Russian Federation
| | - Ekaterina M Ryabchevskaya
- a Department of Virology, Faculty of Biology, Lomonosov Moscow State University , Moscow , Russian Federation
| | - Joseph G Atabekov
- a Department of Virology, Faculty of Biology, Lomonosov Moscow State University , Moscow , Russian Federation
| | - Olga V Karpova
- a Department of Virology, Faculty of Biology, Lomonosov Moscow State University , Moscow , Russian Federation
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7
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Ebeling J, Knispel H, Fünfhaus A, Genersch E. The biological role of the enigmatic C3larvinAB toxin of the honey bee pathogenic bacterium Paenibacillus larvae. Environ Microbiol 2019; 21:3091-3106. [PMID: 31187922 DOI: 10.1111/1462-2920.14709] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 06/03/2019] [Accepted: 06/09/2019] [Indexed: 11/30/2022]
Abstract
Paenibacillus larvae is the causative agent of the notifiable epizootic American foulbrood, a fatal bacterial disease of honey bee larvae. The species P. larvae has been classified into four differentially virulent and prevalent genotypes (ERIC I-IV), which also differ in their virulence factor equipment. Recently, a novel P. larvae toxin, the C3-like C3larvin, has been described. Genome analysis now revealed that the C3larvin gene is actually a part of a toxin locus encompassing two genes encoding a binary AB toxin with the A subunit being C3larvin (C3larvinA) and a putative B subunit (C3larvinB) encoded by the second gene. Sequence and structural analyses demonstrated that C3larvinB is a homologue of the Bacillus anthracis protective antigen (PA), the B subunit of anthrax toxin. The C3larvinAB toxin locus was interrupted by point mutations in all analysed P. larvae ERIC I and ERIC II strains. Only one P. larvae ERIC III/IV strain harboured an uninterrupted toxin locus comprising full-length genes for C3larvinA and B. Exposure bioassays did not substantiate a role as virulence factor for C3larvinAB in P. larvae ERIC I/II. However, the PA homologue C3larvinB had an influence on the virulence of the unique P. larvae strain expressing the functional C3larvinAB locus.
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Affiliation(s)
- Julia Ebeling
- Department of Molecular Microbiology and Bee Diseases, Institute for Bee Research, 16540, Hohen Neuendorf, Germany
| | - Henriette Knispel
- Department of Molecular Microbiology and Bee Diseases, Institute for Bee Research, 16540, Hohen Neuendorf, Germany
| | - Anne Fünfhaus
- Department of Molecular Microbiology and Bee Diseases, Institute for Bee Research, 16540, Hohen Neuendorf, Germany
| | - Elke Genersch
- Department of Molecular Microbiology and Bee Diseases, Institute for Bee Research, 16540, Hohen Neuendorf, Germany.,Freie Universität Berlin, Fachbereich Veterinärmedizin, Institut für Mikrobiologie und Tierseuchen, 14163, Berlin, Germany
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Human monoclonal anti-protective antigen antibody for the low-dose post-exposure prophylaxis and treatment of Anthrax. BMC Infect Dis 2018; 18:640. [PMID: 30526504 PMCID: PMC6288905 DOI: 10.1186/s12879-018-3542-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 11/23/2018] [Indexed: 12/21/2022] Open
Abstract
Background Disease caused by Bacillus anthracis is often accompanied by high mortality primarily due to toxin-mediated injury. In the early disease course, anthrax toxins are secreted; thus, antibiotic use is limited to the early stage. In this regard, antibodies against the toxin component, protective antigen (PA), play an important role in protecting against anthrax. Therefore, we developed PA21, a fully human anti-PA immunoglobulin G monoclonal antibody. Methods Combining human Fab was screened from a phage library with human heavy constant regions. Enzyme-linked immune sorbent assay, Western blot analysis and immunoprecipitation test evaluated the binding ability of PA21. Moreover, the affinity and neutralizing activity of the antibody was detected in vitro while the protective effectiveness in 60 rats was also examined in vivo. Results The Fischer 344 rats challenged with the lethal toxin can be protected by PA21 at a concentration of 0.067 mg/kg. All six rats remained alive although PA21 was injected 24 h before the toxin challenge. PA21 did not influence the binding of PA to cell receptors and that of a lethal factor to PA. Conclusion The PA21 monoclonal antibody against PA can be used for emergency prophylaxis and anthrax treatment.
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Scott H, Huang W, Bann JG, Taylor DJ. Advances in structure determination by cryo-EM to unravel membrane-spanning pore formation. Protein Sci 2018; 27:1544-1556. [PMID: 30129169 PMCID: PMC6194281 DOI: 10.1002/pro.3454] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2018] [Revised: 06/10/2018] [Accepted: 06/11/2018] [Indexed: 01/03/2023]
Abstract
The beta pore-forming proteins (β-PFPs) are a large class of polypeptides that are produced by all Kingdoms of life to contribute to their species' own survival. Pore assembly is a sophisticated multi-step process that includes receptor/membrane recognition and oligomerization events, and is ensued by large-scale structural rearrangements, which facilitate maturation of a prepore into a functional membrane spanning pore. A full understanding of pore formation, assembly, and maturation has traditionally been hindered by a lack of structural data; particularly for assemblies representing differing conformations of functional pores. However, recent advancements in cryo-electron microscopy (cryo-EM) techniques have provided the opportunity to delineate the structures of such flexible complexes, and in different states, to near-atomic resolution. In this review, we place a particular emphasis on the use of cryo-EM to uncover the mechanistic details including architecture, activation, and maturation for some of the prominent members of this family.
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Affiliation(s)
- Harry Scott
- Department of PharmacologyCase Western Reserve UniversityClevelandOhio44106
| | - Wei Huang
- Department of PharmacologyCase Western Reserve UniversityClevelandOhio44106
| | - James G. Bann
- Department of ChemistryWichita State UniversityWichitaKansas67260
| | - Derek J. Taylor
- Department of PharmacologyCase Western Reserve UniversityClevelandOhio44106
- Department of BiochemistryCase Western Reserve UniversityClevelandOhio44106
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10
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Abstract
The complementary actions of the innate and adaptive immune systems often provide effective host defense against microbial pathogens and harmful environmental agents. Germline-encoded pattern recognition receptors (PRRs) endow the innate immune system with the ability to detect and mount a rapid response against a given threat. Members of several intracellular PRR families, including the nucleotide-binding domain and leucine-rich repeat containing receptors (NLRs), the AIM2-like receptors (ALRs), and the tripartite motif-containing (TRIM) protein Pyrin/TRIM20, nucleate the formation of inflammasomes. These cytosolic scaffolds serve to recruit and oligomerize the cysteine protease caspase-1 in filaments that promote its proximity-induced autoactivation. This oligomerization occurs either directly or indirectly through intervention of the bipartite adaptor protein ASC, apoptosis-associated speck-like protein containing a caspase recruitment domain (CARD), which is needed for the domain interaction. Caspase-1 cleaves the precursors of the inflammatory cytokines interleukin (IL)-1β and IL-18 and triggers their release into the extracellular space, where they act on effector cells to promote both local and systemic immune responses. Additionally, inflammasome activation gives rise to a lytic mode of cell death, named pyroptosis, which is thought to contribute to initial host defense against infection by eliminating replication niches of intracellular pathogens and exposing them to the immune system. Inflammasome-induced host defense responses are the subject of intense investigation, and understanding their physiological roles during infection and the regulatory circuits that are involved is becoming increasingly detailed. Here, we discuss current understanding of the activation mechanisms and biological outcomes of inflammasome activation.
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Affiliation(s)
- Hanne Dubois
- NOD-like Receptor and Inflammasome Laboratory, Inflammation Research Center, VIB, 9052, Zwijnaarde, Belgium.,Department of Internal Medicine, Ghent University, 9000, Ghent, Belgium
| | - Andy Wullaert
- NOD-like Receptor and Inflammasome Laboratory, Inflammation Research Center, VIB, 9052, Zwijnaarde, Belgium.,Department of Internal Medicine, Ghent University, 9000, Ghent, Belgium
| | - Mohamed Lamkanfi
- NOD-like Receptor and Inflammasome Laboratory, Inflammation Research Center, VIB, 9052, Zwijnaarde, Belgium. .,Department of Internal Medicine, Ghent University, 9000, Ghent, Belgium.
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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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12
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Ohanjanian L, Remy KE, Li Y, Cui X, Eichacker PQ. An overview of investigational toxin-directed therapies for the adjunctive management of Bacillus anthracis infection and sepsis. Expert Opin Investig Drugs 2015; 24:851-65. [PMID: 25920540 DOI: 10.1517/13543784.2015.1041587] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
INTRODUCTION Sepsis with Bacillus anthracis infection has a very high mortality rate despite appropriate antibiotic and supportive therapies. Over the past 15 years, recent outbreaks in the US and in Europe, coupled with anthrax's bioterrorism weapon potential, have stimulated efforts to develop adjunctive therapies to improve clinical outcomes. Since lethal toxin and edema toxin (LT and ET) make central contributions to the pathogenesis of B. anthracis, these have been major targets in this effort. AREAS COVERED Here, the authors review different investigative biopharmaceuticals that have been recently identified for their therapeutic potential as inhibitors of LT or ET. Among these inhibitors are two antibody preparations that have been included in the Strategic National Stockpile (SNS) and several more that have reached Phase I testing. Presently, however, many of these candidate agents have only been studied in vitro and very few tested in bacteria-challenged models. EXPERT OPINION Although a large number of drugs have been identified as potential therapeutic inhibitors of LT and ET, in most cases their testing has been limited. The use of the two SNS antibody therapies during a large-scale exposure to B. anthracis will be difficult. Further testing and development of agents with oral bioavailability and relatively long shelf lives should be a focus for future research.
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Affiliation(s)
- Lernik Ohanjanian
- National Institutes of Health, Clinical Center, Critical Care Medicine Department , Building 10, Room 2C145, Bethesda, MD 20892 , USA +1 301 402 2914 ; +1 301 402 1213 ;
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13
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Lo SY, Säbel CE, Webb MI, Walsby CJ, Siemann S. High metal substitution tolerance of anthrax lethal factor and characterization of its active copper-substituted analogue. J Inorg Biochem 2014; 140:12-22. [DOI: 10.1016/j.jinorgbio.2014.06.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 05/27/2014] [Accepted: 06/16/2014] [Indexed: 01/19/2023]
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Gurnev PA, Nestorovich EM. Channel-forming bacterial toxins in biosensing and macromolecule delivery. Toxins (Basel) 2014; 6:2483-540. [PMID: 25153255 PMCID: PMC4147595 DOI: 10.3390/toxins6082483] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 08/08/2014] [Accepted: 08/08/2014] [Indexed: 12/19/2022] Open
Abstract
To intoxicate cells, pore-forming bacterial toxins are evolved to allow for the transmembrane traffic of different substrates, ranging from small inorganic ions to cell-specific polypeptides. Recent developments in single-channel electrical recordings, X-ray crystallography, protein engineering, and computational methods have generated a large body of knowledge about the basic principles of channel-mediated molecular transport. These discoveries provide a robust framework for expansion of the described principles and methods toward use of biological nanopores in the growing field of nanobiotechnology. This article, written for a special volume on "Intracellular Traffic and Transport of Bacterial Protein Toxins", reviews the current state of applications of pore-forming bacterial toxins in small- and macromolecule-sensing, targeted cancer therapy, and drug delivery. We discuss the electrophysiological studies that explore molecular details of channel-facilitated protein and polymer transport across cellular membranes using both natural and foreign substrates. The review focuses on the structurally and functionally different bacterial toxins: gramicidin A of Bacillus brevis, α-hemolysin of Staphylococcus aureus, and binary toxin of Bacillus anthracis, which have found their "second life" in a variety of developing medical and technological applications.
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Affiliation(s)
- Philip A Gurnev
- Physics Department, University of Massachusetts, Amherst, MA 01003, USA.
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15
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Santiesteban OJ, Kaittanis C, Perez JM. Identification of toxin inhibitors using a magnetic nanosensor-based assay. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2014; 10:1202-1211. [PMID: 24339142 DOI: 10.1002/smll.201301824] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Revised: 09/12/2013] [Indexed: 06/03/2023]
Abstract
A magnetic nanosensor-based method is described to screen a library of drugs for potential binding to toxins. Screening is performed by measuring changes in the magnetic relaxation signal of the nanosensors (bMR nanosensors) in aqueous suspension upon addition of the toxin. The Anthrax lethal factor (ALF) is selected as a model toxin to test the ability of our bMR nanosensor-based screening method to identify potential inhibitors of the toxin. Out of 30 molecules screened, sulindac, naproxen and fusaric acid are found to bind LF, with dissociation constants in the low micromolar range. Further biological analysis of the free molecules in solution indicate that sulindac and its metabolic products inhibited LF cytotoxicity to macrophages with IC50 values in the micromolar range. Meanwhile, fusaric acid is found to be less effective at inhibiting LF cytotoxicity, while naproxen does not inhibit LF toxicity. Most importantly, when the sulindac and fusaric acid-bMR nanosensors themselves are tested as LF inhibitors, as opposed to the corresponding free molecules, they are stronger inhibitors of LF with IC50 values in the nanomolar range. Taken together, these studies show that a bMR nanosensors-based assay can be used to screen known drugs and other small molecules for inhibitor of toxins. The method can be easily modified to screen for inhibitors of other molecular interactions and not only the selected free molecule can be study as potential inhibitors but also the bMR nanosensors themselves achieving greater inhibitory potential.
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Affiliation(s)
- Oscar J Santiesteban
- NanoScience Technology Center, 12424 Research Parway, Suite 400, University of Central Florida, Orlando, FL, 32826, USA; Department of Chemistry, 4111 Libra Drive, Physical Sciences Bld, Room 255, University of Central Florida, Orlando, FL, 32826, USA
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16
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Dennis MK, Mogridge J. A protective antigen mutation increases the pH threshold of anthrax toxin receptor 2-mediated pore formation. Biochemistry 2014; 53:2166-71. [PMID: 24641616 PMCID: PMC3985898 DOI: 10.1021/bi5000756] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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Anthrax toxin protective antigen
(PA) binds cellular receptors
and self-assembles into oligomeric prepores. A prepore converts to
a protein translocating pore after it has been transported to an endosome
where the low pH triggers formation of a membrane-spanning β-barrel
channel. Formation of this channel occurs after some PA–receptor
contacts are broken to allow pore formation, while others are retained
to preserve receptor association. The interaction between PA and anthrax
toxin receptor 1 (ANTXR1) is weaker than its interaction with ANTXR2
such that the pH threshold of ANTXR1-mediated pore formation is higher
by 1 pH unit. Here we examine receptor-specific differences in toxin
binding and pore formation by mutating PA residue G342 that selectively
abuts ANTXR2. Mutation of G342 to valine, leucine, isoleucine, or
tryptophan increased the amount of PA bound to ANTXR1-expressing cells
and decreased the amount of PA bound to ANTXR2-expressing cells. The
more conservative G342A mutation did not affect the level of binding
to ANTXR2, but ANTXR2-bound PA-G342A prepores exhibited a pH threshold
higher than that of wild-type prepores. Mixtures of wild-type PA and
PA-G342A were functional in toxicity assays, and the pH threshold
of ANTXR2-mediated pore formation was dictated by the relative amounts
of the two proteins in the hetero-oligomers. These results suggest
that PA subunits within an oligomer do not have to be triggered simultaneously
for a productive membrane insertion event to occur.
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Affiliation(s)
- Melissa K Dennis
- Department of Laboratory Medicine and Pathobiology, University of Toronto , Toronto, Ontario M5S 1A8, Canada
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17
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Abstract
INTRODUCTION Present-day rational drug design approaches are based on exploiting unique features of the target biomolecules, small- or macromolecule drug candidates and physical forces that govern their interactions. The 2013 Nobel Prize in chemistry awarded 'for the development of multiscale models for complex chemical systems' once again demonstrated the importance of the tailored drug discovery that reduces the role of the trial-and-error approach to a minimum. The intentional dissemination of Bacillus anthracis spores in 2001 via the so-called anthrax letters has led to increased efforts, politically and scientifically, to develop medical countermeasures that will protect people from the threat of anthrax bioterrorism. AREAS COVERED This article provides an overview of the recent rational drug design approaches for discovering inhibitors of anthrax toxin. The review also directs the readers to the vast literature on the recognized advances and future possibilities in the field. EXPERT OPINION Existing options to combat anthrax toxin lethality are limited. With the only anthrax toxin inhibiting therapy (protective antigen-targeting with a monoclonal antibody, raxibacumab) approved to treat inhalational anthrax, the situation, in our view, is still insecure. Further, the FDA's animal rule for drug approval, which clears compounds without validated efficacy studies on humans, creates a high level of uncertainty, especially when a well-characterized animal model does not exist. Better identification and validation of anthrax toxin therapeutic targets at the molecular level as well as elucidation of the parameters determining the corresponding therapeutic windows are still necessary for more effective therapeutic options.
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Affiliation(s)
- Ekaterina M Nestorovich
- The Catholic University of America, Department of Biology , Washington, DC , USA +1 202 319 6723 ;
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18
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Chadegani F, Lovell S, Mullangi V, Miyagi M, Battaile KP, Bann JG. (19)F nuclear magnetic resonance and crystallographic studies of 5-fluorotryptophan-labeled anthrax protective antigen and effects of the receptor on stability. Biochemistry 2014; 53:690-701. [PMID: 24387629 PMCID: PMC3985773 DOI: 10.1021/bi401405s] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
The anthrax protective antigen (PA)
is an 83 kDa protein that is
one of three protein components of the anthrax toxin, an AB toxin
secreted by Bacillus anthracis. PA is capable of
undergoing several structural changes, including oligomerization to
either a heptameric or octameric structure called the prepore, and
at acidic pH a major conformational change to form a membrane-spanning
pore. To follow these structural changes at a residue-specific level,
we have conducted initial studies in which we have biosynthetically
incorporated 5-fluorotryptophan (5-FTrp) into PA, and we have studied
the influence of 5-FTrp labeling on the structural stability of PA
and on binding to the host receptor capillary morphogenesis protein
2 (CMG2) using 19F nuclear magnetic resonance (NMR). There
are seven tryptophans in PA, but of the four domains in PA, only two
contain tryptophans: domain 1 (Trp65, -90, -136, -206, and -226) and
domain 2 (Trp346 and -477). Trp346 is of particular interest because
of its proximity to the CMG2 binding interface, and because it forms
part of the membrane-spanning pore. We show that the 19F resonance of Trp346 is sensitive to changes in pH, consistent with
crystallographic studies, and that receptor binding significantly
stabilizes Trp346 to both pH and temperature. In addition, we provide
evidence that suggests that resonances from tryptophans distant from
the binding interface are also stabilized by the receptor. Our studies
highlight the positive impact of receptor binding on protein stability
and the use of 19F NMR in gaining insight into structural
changes in a high-molecular weight protein.
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Affiliation(s)
- Fatemeh Chadegani
- Department of Chemistry, Wichita State University , Wichita, Kansas 67260, United States
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19
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Perera AS, Wang H, Shrestha TB, Troyer DL, Bossmann SH. Nanoscopic surfactant behavior of the porin MspA in aqueous media. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2013; 4:278-284. [PMID: 23766950 PMCID: PMC3678404 DOI: 10.3762/bjnano.4.30] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Accepted: 04/12/2013] [Indexed: 06/02/2023]
Abstract
The mycobacterial porin MspA is one of the most stable channel proteins known to date. MspA forms vesicles at low concentrations in aqueous buffers. Evidence from dynamic light scattering, transmission electron microscopy and zeta-potential measurements by electrophoretic light scattering indicate that MspA behaves like a nanoscale surfactant. The extreme thermostability of MspA allows these investigations to be carried out at temperatures as high as 343 K, at which most other proteins would quickly denature. The principles of vesicle formation of MspA as a function of temperature and the underlying thermodynamic factors are discussed here. The results obtained provide crucial evidence in support of the hypothesis that, during vesicle formation, nanoscopic surfactant molecules, such as MspA, deviate from the principles underlined in classical surface chemistry.
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Affiliation(s)
- Ayomi S Perera
- Kansas State University, Department of Chemistry, CBC Building 201, Manhattan, KS 66506, USA
| | - Hongwang Wang
- Kansas State University, Department of Chemistry, CBC Building 201, Manhattan, KS 66506, USA
| | - Tej B Shrestha
- Kansas State University, Department of Anatomy & Physiology, Coles 130, Manhattan, KS 66506, USA
| | - Deryl L Troyer
- Kansas State University, Department of Anatomy & Physiology, Coles 130, Manhattan, KS 66506, USA
| | - Stefan H Bossmann
- Kansas State University, Department of Chemistry, CBC Building 201, Manhattan, KS 66506, USA
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20
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Montpellier LH, Siemann S. Effect of pH on the catalytic function and zinc content of native and immobilized anthrax lethal factor. FEBS Lett 2013; 587:317-21. [DOI: 10.1016/j.febslet.2012.11.035] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2012] [Revised: 11/22/2012] [Accepted: 11/30/2012] [Indexed: 10/27/2022]
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Anthrax toxin protective antigen integrates poly-γ-D-glutamate and pH signals to sense the optimal environment for channel formation. Proc Natl Acad Sci U S A 2012; 109:18378-83. [PMID: 23100533 DOI: 10.1073/pnas.1208280109] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Many toxins assemble into oligomers on the surface of cells. Local chemical cues signal and trigger critical rearrangements of the oligomer, inducing the formation of a membrane-fused or channel state. Bacillus anthracis secretes two virulence factors: a tripartite toxin and a poly-γ-d-glutamic acid capsule (γ-DPGA). The toxin's channel-forming component, protective antigen (PA), oligomerizes to create a prechannel that forms toxic complexes upon binding the two other enzyme components, lethal factor (LF) and edema factor (EF). Following endocytosis into host cells, acidic pH signals the prechannel to form the channel state, which translocates LF and EF into the host cytosol. We report γ-DPGA binds to PA, LF, and EF, exhibiting nanomolar avidity for the PA prechannel oligomer. We show PA channel formation requires the pH-dependent disruption of the intra-PA domain-2-domain-4 (D2-D4) interface. γ-DPGA stabilizes the D2-D4 interface, preventing channel formation both in model membranes and cultured mammalian cells. A 1.9-Å resolution X-ray crystal structure of a D2-D4-interface mutant and corresponding functional studies reveal how stability at the intra-PA interface governs channel formation. We also pinpoint the kinetic pH trigger for channel formation to a residue within PA's membrane-insertion loop at the inter-PA D2-D4 interface. Thus, γ-DPGA may function as a chemical cue, signaling that the local environment is appropriate for toxin assembly but inappropriate for channel formation.
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22
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Hu L, Joshi SB, Andra KK, Thakkar SV, Volkin DB, Bann JG, Middaugh CR. Comparison of the structural stability and dynamic properties of recombinant anthrax protective antigen and its 2-fluorohistidine-labeled analogue. J Pharm Sci 2012; 101:4118-28. [PMID: 22911632 DOI: 10.1002/jps.23294] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Revised: 07/19/2012] [Accepted: 07/31/2012] [Indexed: 01/15/2023]
Abstract
Protective antigen (PA) is the primary protein antigenic component of both the currently used anthrax vaccine and related recombinant vaccines under development. An analogue of recombinant PA (2-FHis rPA) has been recently shown to block the key steps of pore formation in the process of inducing cytotoxicity in cells, and thus can potentially be used as an antitoxin or a vaccine. This rPA analogue was produced by fermentation to incorporate the unnatural amino acid 2-fluorohistidine (2-FHis). In this study, the effects of 2-FHis labeling on rPA antigen's conformational stability and dynamic properties were investigated by various biophysical techniques. Temperature/pH stability profiles of rPA and 2-FHis rPA were analyzed by the empirical phase diagram (EPD) approach, and physical stability differences between them were identified. Results showed that rPA and 2-FHis rPA had similar stability at pH 7-8. With decreasing solution pH, however, 2-FHis rPA was found to be more stable. Dynamic sensitive measurements of the two proteins at pH 5 found that 2-FHis rPA was more dynamic and/or differentially hydrated under acidic pH conditions. The biophysical characterization and stability data provide information useful for the potential development of 2-FHis rPA as a more stable rPA vaccine candidate.
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Affiliation(s)
- Lei Hu
- Macromolecule and Vaccine Stabilization Center, Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, KS 66047, USA
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23
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Mechaly A, Levy H, Epstein E, Rosenfeld R, Marcus H, Ben-Arie E, Shafferman A, Ordentlich A, Mazor O. A novel mechanism for antibody-based anthrax toxin neutralization: inhibition of prepore-to-pore conversion. J Biol Chem 2012; 287:32665-73. [PMID: 22869370 DOI: 10.1074/jbc.m112.400473] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Protective antigen (PA), a key component of anthrax toxin, mediates the entry of lethal factor (LF) or edema factor (EF) through a membranal pore into target cells. We have previously reported the isolation and chimerization of cAb29, an anti-PA monoclonal antibody that effectively neutralizes anthrax toxin in an unknown mechanism. The aim of this study was to elucidate the neutralizing mechanism of this antibody in vitro and to test its ability to confer post-exposure protection against anthrax in vivo. By systematic evaluation of the steps taking place during the PA-based intoxication process, we found that cAb29 did not interfere with the initial steps of intoxication, namely its ability to bind to the anthrax receptor, the consecutive proteolytic cleavage to PA(63), oligomerization, prepore formation, or LF binding. However, the binding of cAb29 to the prepore prevented its pH-triggered transition to the transmembranal pore, thus preventing the last step of intoxication, i.e. the translocation of LF/EF into the cell. Epitope mapping, using a phage display peptide library, revealed that cAb29 binds the 2α(1) loop in domain 2 of PA, a loop that undergoes major conformational changes during pore formation. In vivo, we found that 100% of anthrax-infected rabbits survived when treated with cAb29 12 h after exposure. In conclusion, these experiments demonstrate that cAb29 exerts its potent neutralizing activity in a unique manner by blocking the prepore-to-pore conversion process.
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Affiliation(s)
- Adva Mechaly
- Department of Infectious Diseases, Israel Institute for Biological Research, Ness-Ziona 74100, Israel
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24
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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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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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