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Chen H, Ang CJ, Crowder MK, Brieher WM, Blanke SR. Revisiting bacterial cytolethal distending toxin structure and function. Front Cell Infect Microbiol 2023; 13:1289359. [PMID: 38035327 PMCID: PMC10682658 DOI: 10.3389/fcimb.2023.1289359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 10/19/2023] [Indexed: 12/02/2023] Open
Abstract
Cytolethal distending toxins (CDTs) are intracellular-acting bacterial genotoxins generated by a diverse group of mucocutaneous human pathogens. CDTs must successfully bind to the plasma membrane of host cells in order to exert their modulatory effects. Maximal toxin activity requires all three toxin subunits, CdtA, CdtB, and CdtC, which, based primarily on high-resolution structural data, are believed to preassemble into a tripartite complex necessary for toxin activity. However, biologically active toxin has not been experimentally demonstrated to require assembly of the three subunits into a heterotrimer. Here, we experimentally compared concentration-dependent subunit interactions and toxin cellular activity of the Campylobacter jejuni CDT (Cj-CDT). Co-immunoprecipitation and dialysis retention experiments provided evidence for the presence of heterotrimeric toxin complexes, but only at concentrations of Cj-CdtA, Cj-CdtB, and Cj-CdtC several logs higher than required for Cj-CDT-mediated arrest of the host cell cycle at the G2/M interface, which is triggered by the endonuclease activity associated with the catalytic Cj-CdtB subunit. Microscale thermophoresis confirmed that Cj-CDT subunit interactions occur with low affinity. Collectively, our data suggest that at the lowest concentrations of toxin sufficient for arrest of cell cycle progression, mixtures of Cj-CdtA, Cj-CdtB, and Cj-CdtC consist primarily of non-interacting, subunit monomers. The lack of congruence between toxin tripartite structure and cellular activity suggests that the widely accepted model that CDTs principally intoxicate host cells as preassembled heterotrimeric structures should be revisited.
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Affiliation(s)
- Henry Chen
- Department of Microbiology, School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Claire J. Ang
- Department of Microbiology, School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Molly K. Crowder
- Department of Microbiology, School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - William M. Brieher
- Department of Cellular and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Steven R. Blanke
- Department of Microbiology, School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Biomedical and Translational Sciences Department, Carle-Illinois College of Medicine, University of Illinois, Urbana, IL, United States
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Roussin M, Salcedo SP. NAD+-targeting by bacteria: an emerging weapon in pathogenesis. FEMS Microbiol Rev 2021; 45:6315328. [PMID: 34223888 DOI: 10.1093/femsre/fuab037] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Accepted: 07/01/2021] [Indexed: 11/14/2022] Open
Abstract
Nicotinamide adenine dinucleotide (NAD+) is a major cofactor in redox reactions in all lifeforms. A stable level of NAD+ is vital to ensure cellular homeostasis. Some pathogens can modulate NAD+ metabolism to their advantage and even utilize or cleave NAD+ from the host using specialized effectors known as ADP-ribosyltransferase toxins and NADases, leading to energy store depletion, immune evasion, or even cell death. This review explores recent advances in the field of bacterial NAD+-targeting toxins, highlighting the relevance of NAD+ modulation as an emerging pathogenesis strategy. In addition, we discuss the role of specific NAD+-targeting toxins in niche colonization and bacterial lifestyle as components of Toxin/Antitoxin systems and key players in inter-bacterial competition. Understanding the mechanisms of toxicity, regulation, and secretion of these toxins will provide interesting leads in the search for new antimicrobial treatments in the fight against infectious diseases.
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Affiliation(s)
- Morgane Roussin
- Laboratory of Molecular Microbiology and Structural Biochemistry, Centre National de la Recherche Scientifique UMR5086, Université de Lyon, Lyon, France
| | - Suzana P Salcedo
- Laboratory of Molecular Microbiology and Structural Biochemistry, Centre National de la Recherche Scientifique UMR5086, Université de Lyon, Lyon, France
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Phobalysin: Fisheye View of Membrane Perforation, Repair, Chemotaxis and Adhesion. Toxins (Basel) 2019; 11:toxins11070412. [PMID: 31315179 PMCID: PMC6669599 DOI: 10.3390/toxins11070412] [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: 05/29/2019] [Revised: 07/04/2019] [Accepted: 07/11/2019] [Indexed: 11/30/2022] Open
Abstract
Phobalysin P (PhlyP, for photobacterial lysin encoded on a plasmid) is a recently described small β-pore forming toxin of Photobacterium damselae subsp. damselae (Pdd). This organism, belonging to the family of Vibrionaceae, is an emerging pathogen of fish and various marine animals, which occasionally causes life-threatening soft tissue infections and septicemia in humans. By using genetically modified Pdd strains, PhlyP was found to be an important virulence factor. More recently, in vitro studies with purified PhlyP elucidated some basic consequences of pore formation. Being the first bacterial small β-pore forming toxin shown to trigger calcium-influx dependent membrane repair, PhlyP has advanced to a revealing model toxin to study this important cellular function. Further, results from co-culture experiments employing various Pdd strains and epithelial cells together with data on other bacterial toxins indicate that limited membrane damage may generally enhance the association of bacteria with target cells. Thereby, remodeling of plasma membrane and cytoskeleton during membrane repair could be involved. In addition, a chemotaxis-dependent attack-and track mechanism influenced by environmental factors like salinity may contribute to PhlyP-dependent association of Pdd with cells. Obviously, a synoptic approach is required to capture the regulatory links governing the interaction of Pdd with target cells. The characterization of Pdd’s secretome may hold additional clues because it may lead to the identification of proteases activating PhlyP’s pro-form. Current findings on PhlyP support the notion that pore forming toxins are not just killer proteins but serve bacteria to fulfill more subtle functions, like accessing their host.
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McCallum M, Tammam S, Little DJ, Robinson H, Koo J, Shah M, Calmettes C, Moraes TF, Burrows LL, Howell PL. PilN Binding Modulates the Structure and Binding Partners of the Pseudomonas aeruginosa Type IVa Pilus Protein PilM. J Biol Chem 2016; 291:11003-15. [PMID: 27022027 DOI: 10.1074/jbc.m116.718353] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Indexed: 01/05/2023] Open
Abstract
Pseudomonas aeruginosa is an opportunistic bacterial pathogen that expresses type IVa pili. The pilus assembly system, which promotes surface-associated twitching motility and virulence, is composed of inner and outer membrane subcomplexes, connected by an alignment subcomplex composed of PilMNOP. PilM binds to the N terminus of PilN, and we hypothesize that this interaction causes functionally significant structural changes in PilM. To characterize this interaction, we determined the crystal structures of PilM and a PilM chimera where PilM was fused to the first 12 residues of PilN (PilM·PilN(1-12)). Structural analysis, multiangle light scattering coupled with size exclusion chromatography, and bacterial two-hybrid data revealed that PilM forms dimers mediated by the binding of a novel conserved motif in the N terminus of PilM, and binding PilN abrogates this binding interface, resulting in PilM monomerization. Structural comparison of PilM with PilM·PilN(1-12) revealed that upon PilN binding, there is a large domain closure in PilM that alters its ATP binding site. Using biolayer interferometry, we found that the association rate of PilN with PilM is higher in the presence of ATP compared with ADP. Bacterial two-hybrid data suggested the connectivity of the cytoplasmic and inner membrane components of the type IVa pilus machinery in P. aeruginosa, with PilM binding to PilB, PilT, and PilC in addition to PilN. Pull-down experiments demonstrated direct interactions of PilM with PilB and PilT. We propose a working model in which dynamic binding of PilN facilitates functionally relevant structural changes in PilM.
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Affiliation(s)
- Matthew McCallum
- From the Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada, the Program in Molecular Structure and Function, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada
| | - Stephanie Tammam
- the Program in Molecular Structure and Function, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada
| | - Dustin J Little
- From the Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada, the Program in Molecular Structure and Function, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada
| | - Howard Robinson
- the Photon Sciences Division, Brookhaven National Laboratory, Upton, New York 11973-5000, and
| | - Jason Koo
- the Program in Molecular Structure and Function, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada
| | - Megha Shah
- From the Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Charles Calmettes
- From the Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Trevor F Moraes
- From the Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Lori L Burrows
- the Department of Biochemistry and Biomedical Sciences and the Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario L8N 3Z5, Canada
| | - P Lynne Howell
- From the Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada, the Program in Molecular Structure and Function, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada,
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Benitez JA, Silva AJ. Vibrio cholerae hemagglutinin(HA)/protease: An extracellular metalloprotease with multiple pathogenic activities. Toxicon 2016; 115:55-62. [PMID: 26952544 DOI: 10.1016/j.toxicon.2016.03.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 02/29/2016] [Accepted: 03/03/2016] [Indexed: 01/22/2023]
Abstract
Vibrio cholerae of serogroup O1 and O139, the etiological agent of the diarrheal disease cholera, expresses the extracellular Zn-dependent metalloprotease hemagglutinin (HA)/protease also reported as vibriolysin. This enzyme is also produced by non-O1/O139 (non-cholera) strains that cause mild, sporadic illness (i.e. gastroenteritis, wound or ear infections). Orthologs of HA/protease are present in other members of the Vibrionaceae family pathogenic to humans and fish. HA/protease belongs to the M4 neutral peptidase family and displays significant amino acid sequence homology to Pseudomonas aeruginosa elastase (LasB) and Bacillus thermoproteolyticus thermolysin. It exhibits a broad range of potentially pathogenic activities in cell culture and animal models. These activities range from the covalent modification of other toxins, the degradation of the protective mucus barrier and disruption of intestinal tight junctions. Here we review (i) the structure and regulation of HA/protease expression, (ii) its interaction with other toxins and the intestinal mucosa and (iii) discuss the possible role(s) of HA/protease in the pathogenesis of cholera.
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Affiliation(s)
- Jorge A Benitez
- Morehouse School of Medicine Department of Microbiology, Biochemistry and Immunology, 720 Westview Dr., SW Atlanta, GA, 30310, USA.
| | - Anisia J Silva
- Morehouse School of Medicine Department of Microbiology, Biochemistry and Immunology, 720 Westview Dr., SW Atlanta, GA, 30310, USA.
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Matsuzaki Y, Wu H, Nakano T, Nakahari T, Sano K. ATP-association to intrabacterial nanotransportation system in Vibrio cholerae. Med Mol Morphol 2015; 48:225-34. [PMID: 25986680 DOI: 10.1007/s00795-015-0105-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 05/01/2015] [Indexed: 12/12/2022]
Abstract
Vibrio cholerae colonizes the lumen of the proximal small intestine, which has an alkaline environment, and secretes cholera toxin (CT) through a type II secretion machinery. V. cholerae possesses the intrabacterial nanotransportation system (ibNoTS) for transporting CT from the inner portion toward the peripheral portion of the cytoplasm, and this system is controlled by extrabacterial pH. Association of ATP with ibNoTS has not yet been examined in detail. In this study, we demonstrated by immunoelectron microscopy that ibNoTS of V. cholerae under the extrabacterial alkaline condition was inhibited by ATP inhibitors, 2,4-dinitrophenol (DNP), a protonophore, or 8-amino-adenosine which produces inactive form of ATP. The inhibition of CT transport can be reversed by neutralization of DNP. Those inhibitions were associated with decrease of CT secretion by which ibNoTS followed. We propose that ATP closely associates with V. cholerae ibNoTS for transporting CT.
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Affiliation(s)
- Yuji Matsuzaki
- Department of Microbiology and Infection Control, Osaka Medical College, 2-7 Daigaku-machi, Takatsuki-shi, Osaka, 569-8686, Japan
| | - Hong Wu
- Department of Microbiology and Infection Control, Osaka Medical College, 2-7 Daigaku-machi, Takatsuki-shi, Osaka, 569-8686, Japan
| | - Takashi Nakano
- Department of Microbiology and Infection Control, Osaka Medical College, 2-7 Daigaku-machi, Takatsuki-shi, Osaka, 569-8686, Japan
| | - Takashi Nakahari
- Department of Physiology, Osaka Medical College, 2-7 Daigaku-machi, Takatsuki-shi, Osaka, 569-8686, Japan
- Department of Molecular Cell Physiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, 602-8566, Japan
| | - Kouichi Sano
- Department of Microbiology and Infection Control, Osaka Medical College, 2-7 Daigaku-machi, Takatsuki-shi, Osaka, 569-8686, Japan.
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Type II secretion system: A magic beanstalk or a protein escalator. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1568-77. [DOI: 10.1016/j.bbamcr.2013.12.020] [Citation(s) in RCA: 129] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Revised: 12/13/2013] [Accepted: 12/23/2013] [Indexed: 12/12/2022]
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Abstract
Type IV pili (T4P) are multifunctional protein fibers produced on the surfaces of a wide variety of bacteria and archaea. The major subunit of T4P is the type IV pilin, and structurally related proteins are found as components of the type II secretion (T2S) system, where they are called pseudopilins; of DNA uptake/competence systems in both Gram-negative and Gram-positive species; and of flagella, pili, and sugar-binding systems in the archaea. This broad distribution of a single protein family implies both a common evolutionary origin and a highly adaptable functional plan. The type IV pilin is a remarkably versatile architectural module that has been adopted widely for a variety of functions, including motility, attachment to chemically diverse surfaces, electrical conductance, acquisition of DNA, and secretion of a broad range of structurally distinct protein substrates. In this review, we consider recent advances in this research area, from structural revelations to insights into diversity, posttranslational modifications, regulation, and function.
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Lee KM, Park Y, Bari W, Yoon MY, Go J, Kim SC, Lee HI, Yoon SS. Activation of cholera toxin production by anaerobic respiration of trimethylamine N-oxide in Vibrio cholerae. J Biol Chem 2012; 287:39742-52. [PMID: 23019319 DOI: 10.1074/jbc.m112.394932] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Vibrio cholerae is a gram-negative bacterium that causes cholera. Although the pathogenesis caused by this deadly pathogen takes place in the intestine, commonly thought to be anaerobic, anaerobiosis-induced virulence regulations are not fully elucidated. Anerobic growth of the V. cholerae strain, N16961, was promoted when trimethylamine N-oxide (TMAO) was used as an alternative electron acceptor. Strikingly, cholera toxin (CT) production was markedly induced during anaerobic TMAO respiration. N16961 mutants unable to metabolize TMAO were incapable of producing CT, suggesting a mechanistic link between anaerobic TMAO respiration and CT production. TMAO reductase is transported to the periplasm via the twin arginine transport (TAT) system. A similar defect in both anaerobic TMAO respiration and CT production was also observed in a N16961 TAT mutant. In contrast, the abilities to grow on TMAO and to produce CT were not affected in a mutant of the general secretion pathway. This suggests that V. cholerae may utilize the TAT system to secrete CT during TMAO respiration. During anaerobic growth with TMAO, N16961 cells exhibit green fluorescence when stained with 2',7'-dichlorofluorescein diacetate, a specific dye for reactive oxygen species (ROS). Furthermore, CT production was decreased in the presence of an ROS scavenger suggesting a positive role of ROS in regulating CT production. When TMAO was co-administered to infant mice infected with N16961, the mice exhibited more severe pathogenic symptoms. Together, our results reveal a novel anaerobic growth condition that stimulates V. cholerae to produce its major virulence factor.
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Affiliation(s)
- Kang-Mu Lee
- Department of Microbiology and Immunology, Brain Korea 21 Project for Medical Sciences, Seoul, 120-752 Korea
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Ayers M, Howell PL, Burrows LL. Architecture of the type II secretion and type IV pilus machineries. Future Microbiol 2010; 5:1203-18. [PMID: 20722599 DOI: 10.2217/fmb.10.76] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Motility and protein secretion are key processes contributing to bacterial virulence. A wealth of phylogenetic, biochemical and structural evidence support the hypothesis that the widely distributed type IV pilus (T4P) system, involved in twitching motility, and the type II secretion (T2S) system, involved in exoprotein release, are descended from a common progenitor. Both are composed of dedicated but dynamic assemblages, which have been proposed to function through alternate polymerization and depolymerization or degradation of pilin-like subunits. While ongoing studies aimed at understanding the details of assembly and function of these systems are leading to new insights, there are still large knowledge gaps with respect to several fundamental aspects of their biology, including the localization and stoichiometry of critical assembly components, and the nature of their interactions. This article highlights recent advances in understanding the architectures of the T4P and T2S systems, and the organization of their inner and outer membrane components. As structural data accumulates, it is becoming increasingly apparent that even components with little-to-no sequence similarity have similar folds, further supporting the idea that both systems function by a similar mechanism.
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Affiliation(s)
- Melissa Ayers
- Department of Biochemistry & Biomedical Sciences and the Michael G. DeGroote Institute for Infectious Diseases Research, McMaster University, Hamilton, ON, Canada
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Nanobody-aided structure determination of the EpsI:EpsJ pseudopilin heterodimer from Vibrio vulnificus. J Struct Biol 2008; 166:8-15. [PMID: 19118632 DOI: 10.1016/j.jsb.2008.11.008] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2008] [Revised: 11/22/2008] [Accepted: 11/24/2008] [Indexed: 11/20/2022]
Abstract
Pseudopilins form the central pseudopilus of the sophisticated bacterial type 2 secretion systems. The crystallization of the EpsI:EpsJ pseudopilin heterodimer from Vibrio vulnificus was greatly accelerated by the use of nanobodies, which are the smallest antigen-binding fragments derived from heavy-chain only camelid antibodies. Seven anti-EpsI:EpsJ nanobodies were generated and co-crystallization of EpsI:EpsJ nanobody complexes yielded several crystal forms very rapidly. In the structure solved, the nanobodies are arranged in planes throughout the crystal lattice, linking layers of EpsI:EpsJ heterodimers. The EpsI:EpsJ dimer observed confirms a right-handed architecture of the pseudopilus, but, compared to a previous structure of the EpsI:EpsJ heterodimer, EpsI differs 6 degrees in orientation with respect to EpsJ; one loop of EpsJ is shifted by approximately 5A due to interactions with the nanobody; and a second loop of EpsJ underwent a major change of 17A without contacts with the nanobody. Clearly, nanobodies accelerate dramatically the crystallization of recalcitrant protein complexes and can reveal conformational flexibility not observed before.
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Structure of the minor pseudopilin EpsH from the Type 2 secretion system of Vibrio cholerae. J Mol Biol 2008; 377:91-103. [PMID: 18241884 PMCID: PMC2275911 DOI: 10.1016/j.jmb.2007.08.041] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2007] [Revised: 08/16/2007] [Accepted: 08/16/2007] [Indexed: 01/07/2023]
Abstract
Many Gram-negative bacteria use the multi-protein type II secretion system (T2SS) to selectively translocate virulence factors from the periplasmic space into the extracellular environment. In Vibrio cholerae the T2SS is called the extracellular protein secretion (Eps) system,which translocates cholera toxin and several enzymes in their folded state across the outer membrane. Five proteins of the T2SS, the pseudopilins, are thought to assemble into a pseudopilus, which may control the outer membrane pore EpsD, and participate in the active export of proteins in a "piston-like" manner. We report here the 2.0 A resolution crystal structure of an N-terminally truncated variant of EpsH, a minor pseudopilin from Vibrio cholerae. While EpsH maintains an N-terminal alpha-helix and C-terminal beta-sheet consistent with the type 4a pilin fold, structural comparisons reveal major differences between the minor pseudopilin EpsH and the major pseudopilin GspG from Klebsiella oxytoca: EpsH contains a large beta-sheet in the variable domain, where GspG contains an alpha-helix. Most importantly, EpsH contains at its surface a hydrophobic crevice between its variable and conserved beta-sheets, wherein a majority of the conserved residues within the EpsH family are clustered. In a tentative model of a T2SS pseudopilus with EpsH at its tip, the conserved crevice faces away from the helix axis. This conserved surface region may be critical for interacting with other proteins from the T2SS machinery.
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Holbourn KP, Shone CC, Acharya KR. A family of killer toxins. Exploring the mechanism of ADP-ribosylating toxins. FEBS J 2006; 273:4579-93. [PMID: 16956368 DOI: 10.1111/j.1742-4658.2006.05442.x] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The ADP-ribosylating toxins (ADPRTs) are a family of toxins that catalyse the hydrolysis of NAD and the transfer of the ADP-ribose moiety onto a target. This family includes many notorious killers, responsible for thousands of deaths annually including: cholera, enterotoxic Escherichia coli, whooping cough, diphtheria and a plethora of Clostridial binary toxins. Despite their notoriety as pathogens, the ADPRTs have been extensively used as cellular tools to study and elucidate the functions of the small GTPases that they target. There are four classes of ADPRTs and at least one structure representative of each of these classes has been determined. They all share a common fold and several motifs around the active site that collectively facilitate the binding and transfer of the ADP-ribose moiety of NAD to their protein targets. In this review, we present an overview of the physiology and cellular qualities of the bacterial ADPRTs and take an in-depth look at the structural motifs that differentiate the different classes of bacterial ADPRTs in relation to their function.
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Fan E, O'Neal CJ, Mitchell DD, Robien MA, Zhang Z, Pickens JC, Tan XJ, Korotkov K, Roach C, Krumm B, Verlinde CLMJ, Merritt EA, Hol WGJ. Structural biology and structure-based inhibitor design of cholera toxin and heat-labile enterotoxin. Int J Med Microbiol 2004; 294:217-23. [PMID: 15532979 DOI: 10.1016/j.ijmm.2004.07.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Structural biology studies on cholera toxin and the closely related heat-labile enterotoxin from enterotoxigenic Escherichia coli over the past decade have shed light on the mechanism of toxin action at molecular and atomic levels. Also, components of the extracellular protein secretion apparatus that translocate the toxins across the outer membrane are being investigated. At the same time, structure-based design has led to various classes of compounds targeting different toxin sites, including highly potent multivalent inhibitors that block the toxin receptor-binding process.
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Affiliation(s)
- Erkang Fan
- Department of Biochemistry, Biomolecular Structure Center, University of Washington, Box 357742, Seattle WA 98195, USA
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Kirn TJ, Bose N, Taylor RK. Secretion of a soluble colonization factor by the TCP type 4 pilus biogenesis pathway in Vibrio cholerae. Mol Microbiol 2003; 49:81-92. [PMID: 12823812 DOI: 10.1046/j.1365-2958.2003.03546.x] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Colonization of the human small intestine by Vibrio cholerae requires the type 4 toxin co-regulated pilus (TCP). Genes encoding the structure and biogenesis functions of TCP are organized within an operon located on the Vibrio Pathogenicity Island (VPI). In an effort to elucidate the functions of proteins involved in TCP biogenesis, in frame deletions of all of the genes within the tcp operon coding for putative pilus biogenesis proteins have been constructed and the resulting mutants characterized with respect to the assembly and function of TCP. As a result of this analysis, we have identified the product of one of these genes, tcpF, as a novel secreted colonization factor. Chromosomal deletion of tcpF yields a mutant that retains in vitro phenotypes associated with the assembly of functional TCP yet is severely attenuated for colonization of the infant mouse intestine. Furthermore, we have determined that the mechanism by which TcpF is translocated across the bacterial outer membrane requires the TCP biogenesis machinery and is independent of the type II extracellular protein secretion (EPS) system. These results suggest a dual role for the TCP biogenesis apparatus in V. cholerae pathogenesis and a novel mechanism of intestinal colonization mediated by a soluble factor.
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Affiliation(s)
- Thomas J Kirn
- Dartmouth Medical School, Department of Microbiology and Immunology, Hanover, NH 03755, USA
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Bose N, Payne SM, Taylor RK. Type 4 pilus biogenesis and type II-mediated protein secretion by Vibrio cholerae occur independently of the TonB-facilitated proton motive force. J Bacteriol 2002; 184:2305-9. [PMID: 11914364 PMCID: PMC134947 DOI: 10.1128/jb.184.8.2305-2309.2002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Vibrio cholerae, elaboration of toxin-coregulated pilus and protein secretion by the extracellular protein secretion apparatus occurred in the absence of both TonB systems. In contrast, the cognate putative ATPases were required for each process and could not substitute for each other.
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Affiliation(s)
- Niranjan Bose
- Department of Microbiology and Immunology, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
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Abstract
The type II secretion pathway or the main terminal branch of the general secretion pathway, as it has also been referred to, is widely distributed among Proteobacteria, in which it is responsible for the extracellular secretion of toxins and hydrolytic enzymes, many of which contribute to pathogenesis in both plants and animals. Secretion through this pathway differs from most other membrane transport systems, in that its substrates consist of folded proteins. The type II secretion apparatus is composed of at least 12 different gene products that are thought to form a multiprotein complex, which spans the periplasmic compartment and is specifically required for translocation of the secreted proteins across the outer membrane. This pathway shares many features with the type IV pilus biogenesis system, including the ability to assemble a pilus-like structure. This review discusses recent findings on the organization of the secretion apparatus and the role of its various components in secretion. Different models for pilus-mediated secretion through the gated pore in the outer membrane are also presented, as are the possible properties that determine whether a protein is recognized and secreted by the type II pathway.
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Affiliation(s)
- M Sandkvist
- Department of Biochemistry, American Red Cross, Jerome H. Holland Laboratory, 15601 Crabbs Branch Way, Rockville, MD 20855, USA.
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