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Clarke KR, Hor L, Pilapitiya A, Luirink J, Paxman JJ, Heras B. Phylogenetic Classification and Functional Review of Autotransporters. Front Immunol 2022; 13:921272. [PMID: 35860281 PMCID: PMC9289746 DOI: 10.3389/fimmu.2022.921272] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Accepted: 06/06/2022] [Indexed: 11/30/2022] Open
Abstract
Autotransporters are the core component of a molecular nano-machine that delivers cargo proteins across the outer membrane of Gram-negative bacteria. Part of the type V secretion system, this large family of proteins play a central role in controlling bacterial interactions with their environment by promoting adhesion to surfaces, biofilm formation, host colonization and invasion as well as cytotoxicity and immunomodulation. As such, autotransporters are key facilitators of fitness and pathogenesis and enable co-operation or competition with other bacteria. Recent years have witnessed a dramatic increase in the number of autotransporter sequences reported and a steady rise in functional studies, which further link these proteins to multiple virulence phenotypes. In this review we provide an overview of our current knowledge on classical autotransporter proteins, the archetype of this protein superfamily. We also carry out a phylogenetic analysis of their functional domains and present a new classification system for this exquisitely diverse group of bacterial proteins. The sixteen phylogenetic divisions identified establish sensible relationships between well characterized autotransporters and inform structural and functional predictions of uncharacterized proteins, which may guide future research aimed at addressing multiple unanswered aspects in this group of therapeutically important bacterial factors.
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Affiliation(s)
- Kaitlin R. Clarke
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, Australia
| | - Lilian Hor
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, Australia
| | - Akila Pilapitiya
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, Australia
| | - Joen Luirink
- Department of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit, Amsterdam, Netherlands
| | - Jason J. Paxman
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, Australia
- *Correspondence: Begoña Heras, ; Jason J. Paxman,
| | - Begoña Heras
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, Australia
- *Correspondence: Begoña Heras, ; Jason J. Paxman,
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2
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Vo JL, Ortiz GCM, Totsika M, Lo AW, Hancock SJ, Whitten AE, Hor L, Peters KM, Ageorges V, Caccia N, Desvaux M, Schembri MA, Paxman JJ, Heras B. Variation of Antigen 43 self-association modulates bacterial compacting within aggregates and biofilms. NPJ Biofilms Microbiomes 2022; 8:20. [PMID: 35396507 PMCID: PMC8993888 DOI: 10.1038/s41522-022-00284-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 03/03/2022] [Indexed: 12/13/2022] Open
Abstract
The formation of aggregates and biofilms enhances bacterial colonisation and infection progression by affording protection from antibiotics and host immune factors. Despite these advantages there is a trade-off, whereby bacterial dissemination is reduced. As such, biofilm development needs to be controlled to suit adaptation to different environments. Here we investigate members from one of largest groups of bacterial adhesins, the autotransporters, for their critical role in the assembly of bacterial aggregates and biofilms. We describe the structural and functional characterisation of autotransporter Ag43 variants from different Escherichia coli pathotypes. We show that specific interactions between amino acids on the contacting interfaces of adjacent Ag43 proteins drives a common mode of trans-association that leads to cell clumping. Furthermore, subtle variation of these interactions alters aggregation kinetics and the degree of compacting within cell clusters. Together, our structure–function investigation reveals an underlying molecular basis for variations in the density of bacterial communities.
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Affiliation(s)
- Julieanne L Vo
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, 3086, Australia
| | - Gabriela C Martínez Ortiz
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, 3086, Australia
| | - Makrina Totsika
- Centre for Immunology and Infection Control, School of Biomedical Sciences, Queensland University of Technology, Herston, QLD, 4006, Australia
| | - Alvin W Lo
- School of Chemistry and Molecular Biosciences, and Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Steven J Hancock
- School of Chemistry and Molecular Biosciences, and Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Andrew E Whitten
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW, 2234, Australia
| | - Lilian Hor
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, 3086, Australia
| | - Kate M Peters
- School of Chemistry and Molecular Biosciences, and Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Valentin Ageorges
- Université Clermont Auvergne, INRAE, UMR454 MEDiS, 63000, Clermont-Ferrand, France
| | - Nelly Caccia
- Université Clermont Auvergne, INRAE, UMR454 MEDiS, 63000, Clermont-Ferrand, France
| | - Mickaël Desvaux
- Université Clermont Auvergne, INRAE, UMR454 MEDiS, 63000, Clermont-Ferrand, France
| | - Mark A Schembri
- School of Chemistry and Molecular Biosciences, and Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, 4072, Australia.
| | - Jason J Paxman
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, 3086, Australia.
| | - Begoña Heras
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, 3086, Australia.
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Yasmeen N, Etienne M, Sharma PS, El-Kirat-Chatel S, Helú MB, Kutner W. Molecularly imprinted polymer as a synthetic receptor mimic for capacitive impedimetric selective recognition of Escherichia coli K-12. Anal Chim Acta 2021; 1188:339177. [PMID: 34794582 DOI: 10.1016/j.aca.2021.339177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 10/02/2021] [Accepted: 10/13/2021] [Indexed: 11/28/2022]
Abstract
We fabricated an electrochemical molecularly imprinted polymer (MIP) chemosensor for rapid identification and quantification of E. coli strain using 2-aminophenyl boronic acid as the functional monomer. This strain is a modified Gram-negative strain of Escherichia coli bacterium, an ordinary human gut component. The E. coli strongly interacts with a boronic acid because of porous and flexible polymers of the cell wall. The SEM imaging showed that the bacteria template was partially entrapped within the polymeric matrix in a single step. Moreover, this imaging confirmed E. coli K-12 cell template extraction effectiveness. The prepared MIP determined the E. coli K-12 strain up to 2.9 × 104 cells mL-1. The interference study performed in the presence of E. coli variants expressing different surface appendages (type 1 fimbriae or Antigen 43 protein) or Shewanella oneidensis MR1, another Gram-negative bacteria, demonstrated that the bacterial surface composition notably impacts sensing properties of the bacteria imprinted polymer.
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Affiliation(s)
- Nabila Yasmeen
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224, Warsaw, Poland
| | - Mathieu Etienne
- Université de Lorraine, CNRS, LCPME, F-54000, Nancy, France.
| | - Piyush Sindhu Sharma
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224, Warsaw, Poland.
| | | | | | - Wlodzimierz Kutner
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224, Warsaw, Poland; Faculty of Mathematics and Natural Sciences, School of Sciences, Institute of Chemical Sciences, Cardinal Stefan Wyszynski University in Warsaw, Wóycickiego 1/3, 01-815, Warsaw, Poland
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Yadegari Z, Nikbakht Brujeni G, Ghorbanpour R, Moosakhani F, Lotfollahzadeh S. Molecular characterization of enterotoxigenic Escherichia coli isolated from neonatal calves diarrhea. VETERINARY RESEARCH FORUM : AN INTERNATIONAL QUARTERLY JOURNAL 2019; 10:73-78. [PMID: 31183019 PMCID: PMC6522186 DOI: 10.30466/vrf.2019.34313] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 07/30/2018] [Indexed: 11/29/2022]
Abstract
Enterotoxigenic Escherichia coli (ETEC) produces different virulence factors allowing the bacterium to colonize and develop watery diarrhea. Proteomics studies have also introduced new protein belonging to the secretion pathways, antigen 43 (Ag43), which plays important role in E. coli pathogenesis. The objective of this study was to investigate O-types and virulence factors of E. coli isolates from neonatal calves diarrhea. Total of 120 isolates from diarrheic calves were genotyped for their O groups and the presence of virulence genes K99, F41 and STa as well as Ag43. The predominant O-type was O101 (51.00%) and the prevalence of K99, F41 and STa was 7 (5.80%). The Ag43 was detected in all samples with three different allelic patterns. Our results indicated that K99 positive isolates certainly have one of each 2200 bp or 1800 bp or both copies of Ag43 passenger domain, while negative K99 isolates lack the Ag43. The results reported here provide informative data regarding the prevalence of E. coli O-types and their virulence factors in enteric colibacillosis. The Ag43 that was more found in K99 positive isolates might be associated with diarrhea-causing E. coli strains in neonatal calves.
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Affiliation(s)
- Zahra Yadegari
- Department of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran;
| | - Gholamreza Nikbakht Brujeni
- Department of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran;
| | - Reyhaneh Ghorbanpour
- Department of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran;
| | - Farhad Moosakhani
- Department of Microbiology, Faculty of Veterinary Medicine, Branch of Karaj, Islamic Azad University, Karaj, Iran;
| | - Samad Lotfollahzadeh
- Department of Internal Medicine, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran.
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van 't Hag L, Shen HH, Lu J, Hawley AM, Gras SL, Drummond CJ, Conn CE. Deconvoluting the Effect of the Hydrophobic and Hydrophilic Domains of an Amphiphilic Integral Membrane Protein in Lipid Bicontinuous Cubic Mesophases. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:12025-12034. [PMID: 26488819 DOI: 10.1021/acs.langmuir.5b03256] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Lipidic bicontinuous cubic mesophases with encapsulated amphiphilic proteins are widely used in a range of biological and biomedical applications, including in meso crystallization, as drug delivery vehicles for therapeutic proteins, and as biosensors and biofuel cells. However, the effect of amphiphilic protein encapsulation on the cubic phase nanostructure is not well-understood. In this study, we illustrate the effect of incorporating the bacterial amphiphilic membrane protein Ag43, and its individual hydrophobic β(43) and hydrophilic α(43) domains, in bicontinuous cubic mesophases. For the monoolein, monoalmitolein, and phytantriol cubic phases with and without 8% w/w cholesterol, the effect of the full length amphiphilic protein Ag43 on the cubic phase nanostructure was more significant than the sum of the individual hydrophobic β(43) and hydrophilic α(43) domains. Several factors were found to potentially influence the impact of the hydrophobic β(43) domain on the cubic phase internal nanostructure. These include the size of the hydrophobic β(43) domain relative to the thickness of the lipid bilayer, as well as its charge and diameter. The size of the hydrophilic α(43) domain relative to the water channel radius of the cubic mesophase was also found to be important. The secondary structure of the Ag43 proteins was affected by the hydrophobic thickness and physicochemical properties of the lipid bilayer and the water channel diameter of the cubic phase. Such structural changes may be small but could potentially affect membrane protein function.
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Affiliation(s)
| | | | | | | | | | - Calum J Drummond
- CSIRO Manufacturing Flagship , Clayton, Victoria 3169, Australia
- School of Applied Sciences, College of Science, Engineering and Health, RMIT University , Melbourne, Victoria 3001, Australia
| | - Charlotte E Conn
- School of Applied Sciences, College of Science, Engineering and Health, RMIT University , Melbourne, Victoria 3001, Australia
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Abstract
The autotransporter and two-partner secretion (TPS) pathways are used by E. coli and many other Gram-negative bacteria to delivervirulence factors into the extracellular milieu.Autotransporters arecomprised of an N-terminal extracellular ("passenger") domain and a C-terminal β barrel domain ("β domain") that anchors the protein to the outer membrane and facilitates passenger domain secretion. In the TPS pathway, a secreted polypeptide ("exoprotein") is coordinately expressed with an outer membrane protein that serves as a dedicated transporter. Bothpathways are often grouped together under the heading "type V secretion" because they have many features in common and are used for the secretion of structurally related polypeptides, but it is likely that theyhave distinct evolutionary origins. Although it was proposed many years ago that autotransporterpassenger domains are transported across the outer membrane through a channel formed by the covalently linked β domain, there is increasing evidence that additional factors are involved in the translocation reaction. Furthermore, details of the mechanism of protein secretion through the TPS pathway are only beginning to emerge. In this chapter I discussour current understanding ofboth early and late steps in the biogenesis of polypeptides secreted through type V pathways and current modelsofthe mechanism of secretion.
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Zalewska-Pia Tek B, Pia Tek R, Olszewski M, Kur J. Identification of antigen Ag43 in uropathogenic Escherichia coli Dr+ strains and defining its role in the pathogenesis of urinary tract infections. MICROBIOLOGY-SGM 2015; 161:1034-1049. [PMID: 25743156 DOI: 10.1099/mic.0.000072] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 03/03/2015] [Indexed: 11/18/2022]
Abstract
Urinary tract infections (UTIs) caused by uropathogenic Escherichia coli (UPEC) are amongst the most common bacterial infectious diseases in the developed world. The urovirulence of UPEC is mainly associated with the surface-exposed fimbrial adhesins and adhesins of the autotransporter (AT) family. The best studied of these proteins is antigen Ag43 mediating cell aggregation, adhesion and biofilm development as the causes of chronic UTIs. The E. coli IH11128 Dr(+) (dra (+)) strain of the Dr/Afa(+) family of adhesins possesses two major surface-exposed virulence factors: Dr fimbrial polyadhesin and DraD protein (fimbrial tip subunit or protein component of the adhesive sheath). Here, we identified for the first time, to our knowledge, the agn43 gene encoding Ag43 in the WT clinical isolate of UPEC Dr(+) as a new virulence factor not yet tested. We also found that Dr fimbrial expression, which like Ag43 is under the control of a phase-variable mechanism, did not exclude Ag43 surface presentation. However, the presence of Dr fimbriae supported by other structures on the cell surface caused a physical neutralization of Ag43-mediated autoaggregation during in vitro growth. The fimbrial bundling further increased the distance between the adjacent Ag43(+) cells, thus preventing head-to-tail association between surface-exposed Ag43 subunits and their interactions with the host cells. The investigations showed that Ag43 did not act as a specific adhesin and invasin, conversely to the major virulence factors of E. coli Dr(+), but played significant roles in the viability and metabolic activity of bacterial cells forming biofilm, and in the survival of bacteria within invaded epithelial cells.
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Affiliation(s)
- Beata Zalewska-Pia Tek
- Department of Molecular Biotechnology and Microbiology, Gdansk University of Technology, ul. G. Narutowicza 11/12, 80-233Gdansk, Poland
| | - Rafał Pia Tek
- Department of Molecular Biotechnology and Microbiology, Gdansk University of Technology, ul. G. Narutowicza 11/12, 80-233Gdansk, Poland
| | - Marcin Olszewski
- Department of Molecular Biotechnology and Microbiology, Gdansk University of Technology, ul. G. Narutowicza 11/12, 80-233Gdansk, Poland
| | - Józef Kur
- Department of Molecular Biotechnology and Microbiology, Gdansk University of Technology, ul. G. Narutowicza 11/12, 80-233Gdansk, Poland
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Jacquot A, Sakamoto C, Razafitianamarahavo A, Caillet C, Merlin J, Fahs A, Ghigo JM, Duval JFL, Beloin C, Francius G. The dynamics and pH-dependence of Ag43 adhesins' self-association probed by atomic force spectroscopy. NANOSCALE 2014; 6:12665-12681. [PMID: 25208582 DOI: 10.1039/c4nr03312d] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Self-associating auto-transporter (SAAT) adhesins are two-domain cell surface proteins involved in bacteria auto-aggregation and biofilm formation. Antigen 43 (Ag43) is a SAAT adhesin commonly found in Escherichia coli whose variant Ag43a has been shown to promote persistence of uropathogenic E. coli within the bladder. The recent resolution of the tri-dimensional structure of the 499 amino-acids' β-domain in Ag43a has shed light on the possible mechanism governing the self-recognition of SAAT adhesins, in particular the importance of trans-interactions between the L shaped β-helical scaffold of two α-domains of neighboring adhesins. In this study, we use single-molecule force spectroscopy (SMFS) and dynamic force spectroscopy (DFS) to unravel the dynamics of Ag43-self association under various pH and molecular elongation rate conditions that mimic the situations encountered by E. coli in its natural environment. Results evidenced an important stretchability of Ag43α with unfolding of sub-domains leading to molecular extension as long as 150 nm. Nanomechanical analysis of molecular stretching data suggested that self-association of Ag43 can lead to the formation of dimers and tetramers driven by rapid and weak cis- as well as slow but strong trans-interaction forces with a magnitude as large as 100-250 pN. The dynamics of cis- and trans-interactions were demonstrated to be strongly influenced by pH and applied shear force, thus suggesting that environmental conditions can modulate Ag43-mediated aggregation of bacteria at the molecular level.
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Affiliation(s)
- Adrien Jacquot
- Université de Lorraine, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, Villers-lès-Nancy, F-54601, France
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Immunoproteomic analysis to identify Shiga toxin-producing Escherichia coli outer membrane proteins expressed during human infection. Infect Immun 2014; 82:4767-77. [PMID: 25156722 DOI: 10.1128/iai.02030-14] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Shiga-toxin producing Escherichia coli (STEC) is the etiologic agent of acute diarrhea, dysentery, and hemolytic-uremic syndrome (HUS). There is no approved vaccine for STEC infection in humans, and antibiotic use is contraindicated, as it promotes Shiga toxin production. In order to identify STEC-associated antigens and immunogenic proteins, outer membrane proteins (OMPs) were extracted from STEC O26:H11, O103, O113:H21, and O157:H7 strains, and commensal E. coli strain HS was used as a control. SDS-PAGE, two-dimensional-PAGE analysis, Western blot assays using sera from pediatric HUS patients and controls, and matrix-assisted laser desorption ionization-tandem time of flight analyses were used to identify 12 immunogenic OMPs, some of which were not reactive with control sera. Importantly, seven of these proteins have not been previously reported to be immunogenic in STEC strains. Among these seven proteins, OmpT and Cah displayed IgG and IgA reactivity with sera from HUS patients. Genes encoding these two proteins were present in a majority of STEC strains. Knowledge of the antigens produced during infection of the host and the immune response to those antigens will be important for future vaccine development.
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Francius G, Polyakov P, Merlin J, Abe Y, Ghigo JM, Merlin C, Beloin C, Duval JFL. Bacterial surface appendages strongly impact nanomechanical and electrokinetic properties of Escherichia coli cells subjected to osmotic stress. PLoS One 2011; 6:e20066. [PMID: 21655293 PMCID: PMC3105017 DOI: 10.1371/journal.pone.0020066] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Accepted: 04/17/2011] [Indexed: 11/19/2022] Open
Abstract
The physicochemical properties and dynamics of bacterial envelope, play a major role in bacterial activity. In this study, the morphological, nanomechanical and electrohydrodynamic properties of Escherichia coli K-12 mutant cells were thoroughly investigated as a function of bulk medium ionic strength using atomic force microscopy (AFM) and electrokinetics (electrophoresis). Bacteria were differing according to genetic alterations controlling the production of different surface appendages (short and rigid Ag43 adhesins, longer and more flexible type 1 fimbriae and F pilus). From the analysis of the spatially resolved force curves, it is shown that cells elasticity and turgor pressure are not only depending on bulk salt concentration but also on the presence/absence and nature of surface appendage. In 1 mM KNO(3), cells without appendages or cells surrounded by Ag43 exhibit large Young moduli and turgor pressures (∼700-900 kPa and ∼100-300 kPa respectively). Under similar ionic strength condition, a dramatic ∼50% to ∼70% decrease of these nanomechanical parameters was evidenced for cells with appendages. Qualitatively, such dependence of nanomechanical behavior on surface organization remains when increasing medium salt content to 100 mM, even though, quantitatively, differences are marked to a much smaller extent. Additionally, for a given surface appendage, the magnitude of the nanomechanical parameters decreases significantly when increasing bulk salt concentration. This effect is ascribed to a bacterial exoosmotic water loss resulting in a combined contraction of bacterial cytoplasm together with an electrostatically-driven shrinkage of the surface appendages. The former process is demonstrated upon AFM analysis, while the latter, inaccessible upon AFM imaging, is inferred from electrophoretic data interpreted according to advanced soft particle electrokinetic theory. Altogether, AFM and electrokinetic results clearly demonstrate the intimate relationship between structure/flexibility and charge of bacterial envelope and propensity of bacterium and surface appendages to contract under hypertonic conditions.
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Affiliation(s)
- Grégory Francius
- Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, Nancy Université, CNRS UMR7564, Villers-lès-Nancy, France
| | - Pavel Polyakov
- Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, Nancy Université, CNRS UMR7564, Villers-lès-Nancy, France
| | - Jenny Merlin
- Laboratoire Environnement et Minéralurgie, Nancy Université, CNRS UMR7569, Vandoeuvre-lès-Nancy, France
| | - Yumiko Abe
- Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, Nancy Université, CNRS UMR7564, Villers-lès-Nancy, France
| | - Jean-Marc Ghigo
- Institut Pasteur, Unité de Génétique des Biofilms, Paris, France
- CNRS URA 2172, Paris, France
| | - Christophe Merlin
- Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, Nancy Université, CNRS UMR7564, Villers-lès-Nancy, France
| | - Christophe Beloin
- Institut Pasteur, Unité de Génétique des Biofilms, Paris, France
- CNRS URA 2172, Paris, France
| | - Jérôme F. L. Duval
- Laboratoire Environnement et Minéralurgie, Nancy Université, CNRS UMR7569, Vandoeuvre-lès-Nancy, France
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Effect of glycosylation on the extracellular domain of the Ag43 bacterial autotransporter: enhanced stability and reduced cellular aggregation. Biochem J 2008; 412:563-77. [DOI: 10.1042/bj20071497] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Autotransporters constitute the biggest group of secreted proteins in Gram-negative bacteria and contain a membrane-bound β-domain and a passenger domain secreted to the extracellular environment via an unusually long N-terminal sequence. Several passenger domains are known to be glycosylated by cytosolic glycosyl transferases, promoting bacterial attachment to mammalian cells. In the present study we describe the effect of glycosylation on the extracellular passenger domain of the Escherichia coli autotransporter Ag43α, which induces frizzy colony morphology and cell settling. We identify 16 glycosylation sites and suggest two possible glycosylation motifs for serine and threonine residues. Glycosylation stabilizes against thermal and chemical denaturation and increases refolding kinetics. Unexpectedly, glycosylation also reduces the stabilizing effect of Ca2+ ions, removes the ability of Ca2+ to promote cell adhesion, reduces the ability of Ag43α-containing cells to form bacterial amyloid and increases the susceptibility of the resulting amyloid to proteolysis. In addition, our results indicate that Ag43α folds without a stable intermediate, unlike pertactin, indicating that autotransporters may arrive at the native state by a variety of different mechanisms despite a common overall structure. A small but significant fraction of Ag43α can survive intact in the periplasm if expressed without the β-domain, suggesting that it is able to adopt a protease-resistant structure prior to translocation across the membrane. The present study demonstrates that glycosylation may play significant roles in structural and functional properties of bacterial autotransporters at many different levels.
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14
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Dautin N, Bernstein HD. Protein secretion in gram-negative bacteria via the autotransporter pathway. Annu Rev Microbiol 2007; 61:89-112. [PMID: 17506669 DOI: 10.1146/annurev.micro.61.080706.093233] [Citation(s) in RCA: 219] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Autotransporters are a large and diverse superfamily of proteins produced by pathogenic gram-negative bacteria that are composed of an N-terminal passenger domain, which typically harbors a virulence function, and a C-terminal beta domain. It has long been known that the beta domain anchors the protein to the outer membrane and facilitates transport of the passenger domain into the extracellular space. Despite the apparent simplicity of the autotransporter pathway, several aspects of autotransporter biogenesis remain poorly understood, most notably the mechanism by which the passenger domain is translocated across the outer membrane. Here we review recent evidence that the enormous sequence diversity of both passenger and beta domains belies a remarkable conservation of structure. We also discuss insights into each stage of autotransporter biogenesis that have emerged from recent structural, biochemical, and imaging studies.
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Affiliation(s)
- Nathalie Dautin
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0538, USA.
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15
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Charbonneau ME, Berthiaume F, Mourez M. Proteolytic processing is not essential for multiple functions of the Escherichia coli autotransporter adhesin involved in diffuse adherence (AIDA-I). J Bacteriol 2006; 188:8504-12. [PMID: 17041044 PMCID: PMC1698232 DOI: 10.1128/jb.00864-06] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The Escherichia coli adhesin involved in diffuse adherence (AIDA-I), like many other autotransporter proteins, is released in the periplasm as a proprotein undergoing proteolytic processing after its translocation across the outer membrane. The proprotein is cleaved into a membrane-embedded fragment, AIDAc, and an extracellular fragment, the mature AIDA-I adhesin. The latter remains noncovalently associated with the outer membrane and can be released by heat treatment. The mechanism of cleavage of the proprotein and its role in the functionality of AIDA-I are not understood. Here, we show that cleavage is independent of the amount of AIDA-I in the outer membrane, suggesting an intramolecular autoproteolytic mechanism or a cleavage mediated by an unknown protease. We show that the two fragments, mature AIDA-I and AIDAc, can be cosolubilized and copurified in a folded and active conformation. We observed that the release by heat treatment results from the unfolding of AIDA-I and that the interaction of AIDA-I with AIDAc seems to be disturbed only by denaturation. We constructed an uncleavable point mutant of AIDA-I, where a serine of the cleavage site was changed into a leucine, and showed that adhesion, autoaggregation, and biofilm formation mediated by the mutant are indistinguishable from the wild-type levels. Lastly, we show that both proteins can mediate the invasion of cultured epithelial cells. Taken together, our experiments suggest that the proteolytic processing of AIDA-I plays a minor role in the functionality of this protein.
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Affiliation(s)
- Marie-Eve Charbonneau
- Canada Research Chair on Bacterial Animal Diseases, Université de Montréal, Faculté de Médecine Vétérinaire, 3200 Sicotte, St-Hyacinthe, J2S 7C6, Québec, Canada
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16
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Wegrzyn G, Wegrzyn A. Genetic switches during bacteriophage lambda development. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2005; 79:1-48. [PMID: 16096026 DOI: 10.1016/s0079-6603(04)79001-7] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Affiliation(s)
- Grzegorz Wegrzyn
- Department of Molecular Biology, University of Gdańsk, 80-822 Gdańsk, Poland
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17
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Henderson IR, Navarro-Garcia F, Desvaux M, Fernandez RC, Ala'Aldeen D. Type V protein secretion pathway: the autotransporter story. Microbiol Mol Biol Rev 2004; 68:692-744. [PMID: 15590781 PMCID: PMC539010 DOI: 10.1128/mmbr.68.4.692-744.2004] [Citation(s) in RCA: 595] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Gram-negative bacteria possess an outer membrane layer which constrains uptake and secretion of solutes and polypeptides. To overcome this barrier, bacteria have developed several systems for protein secretion. The type V secretion pathway encompasses the autotransporter proteins, the two-partner secretion system, and the recently described type Vc or AT-2 family of proteins. Since its discovery in the late 1980s, this family of secreted proteins has expanded continuously, due largely to the advent of the genomic age, to become the largest group of secreted proteins in gram-negative bacteria. Several of these proteins play essential roles in the pathogenesis of bacterial infections and have been characterized in detail, demonstrating a diverse array of function including the ability to condense host cell actin and to modulate apoptosis. However, most of the autotransporter proteins remain to be characterized. In light of new discoveries and controversies in this research field, this review considers the autotransporter secretion process in the context of the more general field of bacterial protein translocation and exoprotein function.
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Affiliation(s)
- Ian R Henderson
- Division of Immunity and Infection, University of Birmingham, Birmingham B15 2TT, UK.
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18
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Parham NJ, Srinivasan U, Desvaux M, Foxman B, Marrs CF, Henderson IR. PicU, a second serine protease autotransporter of uropathogenic Escherichia coli. FEMS Microbiol Lett 2004; 230:73-83. [PMID: 14734168 DOI: 10.1016/s0378-1097(03)00862-0] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Escherichia coli is the major aetiological agent of urinary tract infections (UTI). Like diarrhoeagenic strains of E. coli, uropathogenic isolates possess virulence determinants that distinguish them from commensal strains and allow them to produce the clinical manifestations associated with UTI. Several autotransporter proteins have been associated with the ability of E. coli, and other Gram-negative bacteria, to cause disease. Recently, we described the existence within uropathogenic E. coli (UPEC) strains of Sat, a toxin of the serine protease autotransporter of Enterobacteriaceae (SPATE) subfamily. Using features common to proteins secreted via the autotransporter pathway we have identified nine additional autotransporter proteins from the genomic sequence data of UPEC CFT073. Surprisingly, two additional members of the SPATE subfamily were identified. One protein, designated PicU, was homologous to the Pic protein identified in Shigella flexneri and enteroaggregative E. coli. The PicU protein was expressed and investigated for functional activity.
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Affiliation(s)
- Nick J Parham
- Bacterial Pathogenesis and Genomics Unit, Division of Immunity and Infection, The Medical School, University of Birmingham, Edgbaston, UK
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19
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Wehrl W, Brinkmann V, Jungblut PR, Meyer TF, Szczepek AJ. From the inside out - processing of the Chlamydial autotransporter PmpD and its role in bacterial adhesion and activation of human host cells. Mol Microbiol 2004; 51:319-34. [PMID: 14756775 DOI: 10.1046/j.1365-2958.2003.03838.x] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Polymorphic membrane protein (Pmp)21 otherwise known as PmpD is the longest of 21 Pmps expressed by Chlamydophila pneumoniae. Recent bioinformatical analyses annotated PmpD as belonging to a family of exported Gram-negative bacterial proteins designated autotransporters. This prediction, however, was never experimentally supported, nor was the function of PmpD known. Here, using 1D and 2D PAGE we demonstrate that PmpD is processed into two parts, N-terminal (N-pmpD), middle (M-pmpD) and presumably third, C-terminal part (C-pmpD). Based on localization of the external part on the outer membrane as shown by immunofluorescence, immuno-electron microscopy and immunoblotting combined with trypsinization, we demonstrate that N-pmpD translocates to the surface of bacteria where it non-covalently binds other components of the outer membrane. We propose that N-pmpD functions as an adhesin, as antibodies raised against N-pmpD blocked chlamydial infectivity in the epithelial cells. In addition, recombinant N-pmpD activated human monocytes in vitro by upregulating their metabolic activity and by stimulating IL-8 release in a dose-dependent manner. These results demonstrate that N-PmpD is an autotransporter component of chlamydial outer membrane, important for bacterial invasion and host inflammation.
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Affiliation(s)
- Wolfgang Wehrl
- Max-Planck Institute for Infection Biology, Department of Molecular Biology, Schumannstr. 21/22, 10117 Berlin, Germany
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20
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Monteiro-Neto V, Bando SY, Moreira-Filho CA, Girón JA. Characterization of an outer membrane protein associated with haemagglutination and adhesive properties of enteroaggregative Escherichia coli O111:H12. Cell Microbiol 2003; 5:533-47. [PMID: 12864813 DOI: 10.1046/j.1462-5822.2003.00299.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Diarrhoeagenic Escherichia coli strains of serotype O111:H12 are characterized by their aggregative pattern of adherence on cultured epithelial cells and thus are considered enteroaggregative E. coli (EAEC). We have previously shown that these EAEC strains lack the genes encoding the aggregative fimbriae I and II described in other heterologous EAEC strains. In this paper, we show compelling data suggesting that a plasmid-encoded outer membrane 58 kDa protein termed aggregative protein 58 (Ap58) produced by EAEC O111:H12 strains, is associated with the adherence capabilities and haemagglutination of animal red blood cells. This conclusion is supported by several lines of evidence: (i) adherent O111:H12 strains are able to produce Ap58; (ii) non-adherent O111:H12 strains are unable to produce Ap58; (iii) antibodies raised against Ap58 inhibited adherence and haemagglutination of epithelial and bovine red blood cells, respectively; (iv) a non-adherent E. coli K-12 host strain containing the ap58 gene determinant on plasmid pVM15 displayed abundant adherence to cultured HEp-2 cells; and (v) the purified Ap58 bound specifically to HEp-2 and bovine red blood cells. Our findings indicate that the aggregative adherence in the O111:H12 strains may be also mediated by non-fimbrial adhesins. We believe our data contribute to the understanding of the adherence mechanisms of these organisms.
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Affiliation(s)
- Valerio Monteiro-Neto
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, Brazil
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21
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Torres AG, Perna NT, Burland V, Ruknudin A, Blattner FR, Kaper JB. Characterization of Cah, a calcium-binding and heat-extractable autotransporter protein of enterohaemorrhagic Escherichia coli. Mol Microbiol 2002; 45:951-66. [PMID: 12180916 DOI: 10.1046/j.1365-2958.2002.03094.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have identified and characterized a protein of enterohaemorrhagic Escherichia coli (EHEC) serotype O157:H7 that shares homology with antigen 43 and AIDA-I of E. coli. The gene encoding this protein consists of a 2850 bp open reading frame and was named cah for calcium binding antigen 43 homologue. The prototype EHEC strain EDL933 possesses identical duplicate copies of cah (cah1 and cah2), which showed 100% identity at the nucleotide level. We showed that E. coli K-12 containing the recombinant cah gene produced two proteins, an approximately 80 kDa outer membrane protein and a 43.0 kDa heat-extractable protein. The Cah protein contains a predicted 52-amino-acid extended signal sequence found in several autotransporter proteins, and N-terminal sequencing data indicated that the 43.0 kDa passenger protein was derived from cleavage of the signal sequence from alanine at position 53. Phenotypes such as autoaggregation and change in bacterial shape were observed when a recombinant plasmid containing the cah gene was introduced into a laboratory E. coli strain, and these phenotypes were eliminated upon mutation of the cah gene. The passenger domain contains six domains found in calcium-binding proteins, and the recombinant Cah passenger protein bound 45Ca2+. In E. coli O157:H7, Cah is a heat-extractable protein, the expression of which is induced in minimal essential media and under divalent ion-depleting conditions; it also participates in the formation of biofilms. Our results provide insight into the expression, secretion and preliminary features of the calcium-binding Cah autotransporter protein of EHEC O157:H7.
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Affiliation(s)
- Alfredo G Torres
- Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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22
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Gabig M, Herman-Antosiewicz A, Kwiatkowska M, Los M, Thomas MS, Wegrzyn G. The cell surface protein Ag43 facilitates phage infection of Escherichia coli in the presence of bile salts and carbohydrates. MICROBIOLOGY (READING, ENGLAND) 2002; 148:1533-42. [PMID: 11988528 DOI: 10.1099/00221287-148-5-1533] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
It was found that infection of Escherichia coli by bacteriophage lambda is inhibited in the presence of certain bile salts and carbohydrates when cells are in the "OFF" state for production of the phase-variable cell surface protein antigen 43 (Ag43). The inhibition of phage growth was found to be due to a significant impairment in the process of phage adsorption. Expression of the gene encoding Ag43 (agn43) from a plasmid or inactivation of the oxyR gene (encoding an activator of genes important for defence against oxidative stress) suppressed this inhibition. A mutation, rpoA341, in the gene encoding the alpha subunit of RNA polymerase also facilitated phage adsorption in the presence of bile salts and carbohydrates. The rpoA341 mutation promoted efficient production of Ag43 in a genetic background that would otherwise be in the "OFF" phase for expression of the agn43 gene. Analysis of a reporter gene fusion demonstrated that the promoter for the agn43 gene was more active in the rpoA341 mutant than in the otherwise isogenic rpoA(+) strain. The combined inhibitory action of bile salts and carbohydrates on phage adsorption and the abolition of this inhibition by production of Ag43 was not restricted to lambda, as a similar phenomenon was observed for the coliphages P1 and T4.
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Affiliation(s)
- Magdalena Gabig
- Department of Molecular Biology, University of Gdańsk, Kładki 24, 80-822 Gdańsk, Poland
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23
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Waldron DE, Owen P, Dorman CJ. Competitive interaction of the OxyR DNA-binding protein and the Dam methylase at the antigen 43 gene regulatory region in Escherichia coli. Mol Microbiol 2002; 44:509-20. [PMID: 11972787 DOI: 10.1046/j.1365-2958.2002.02905.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The antigen 43 surface protein of Escherichia coli is expressed in a phase-variable manner by a mechanism involving alternative activation and repression of transcription of the agn43 gene. The repressor is the OxyR DNA-binding protein, and its binding site was found to be located downstream of the agn43 transcription start site in a region of DNA that encompasses three 5'-GATC-3' sequences that are subject to Dam-mediated DNA methylation. It has been suggested previously that the phase-variable expression of antigen 43 results from a competition between Dam methylase and the OxyR repressor for these sites. The 5'-GATC-3' sequences were inactivated for methylation by site-directed mutagenesis, and all possible combinations of inactive and active sites were assessed for effects on phase-variable expression of the agn43 gene. Inactivation of any 5'-GATC-3' site individually had no effect; at least two sites had to be inactivated to disrupt the normal pattern of expression. Studies of OxyR interaction with agn43 DNA showed that methylation of any two 5'-GATC-3' sites was necessary and sufficient to block binding of the repressor. It was also found that the adenines of the second and third 5'-GATC-3' sites are required for OxyR binding, demonstrating that the sites for Dam methylation and for repressor binding are intimately associated. This is consistent with a competition model in which Dam and OxyR share a preference for specific DNA sequences in the regulatory region of the agn43 gene.
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Affiliation(s)
- Denise E Waldron
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Republic of Ireland
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24
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Lerouge I, Vanderleyden J. O-antigen structural variation: mechanisms and possible roles in animal/plant-microbe interactions. FEMS Microbiol Rev 2002; 26:17-47. [PMID: 12007641 DOI: 10.1111/j.1574-6976.2002.tb00597.x] [Citation(s) in RCA: 322] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Current data from bacterial pathogens of animals and from bacterial symbionts of plants support some of the more general proposed functions for lipopolysaccharides (LPS) and underline the importance of LPS structural versatility and adaptability. Most of the structural heterogeneity of LPS molecules is found in the O-antigen polysaccharide. In this review, the role and mechanisms of this striking flexibility in molecular structure of the O-antigen in bacterial pathogens and symbionts are illustrated by some recent findings. The variation in O-antigen that gives rise to an enormous structural diversity of O-antigens lies in the sugar composition and the linkages between monosaccharides. The chemical composition and structure of the O-antigen is strain-specific (interstrain LPS heterogeneity) but can also vary within one bacterial strain (intrastrain LPS heterogeneity). Both LPS heterogeneities can be achieved through variations at different levels. First of all, O-polysaccharides can be modified non-stoichiometrically with sugar moieties, such as glucosyl and fucosyl residues. The addition of non-carbohydrate substituents, i.e. acetyl or methyl groups, to the O-antigen can also occur with regularity, but in most cases these modifications are again non-stoichiometric. Understanding LPS structural variation in bacterial pathogens is important because several studies have indicated that the composition or size of the O-antigen might be a reliable indicator of virulence potential and that these important features often differ within the same bacterial strain. In general, O-antigen modifications seem to play an important role at several (at least two) stages of the infection process, including the colonization (adherence) step and the ability to bypass or overcome host defense mechanisms. There are many reports of modifications of O-antigen in bacterial pathogens, resulting either from altered gene expression, from lysogenic conversion or from lateral gene transfer followed by recombination. In most cases, the mechanisms underlying these changes have not been resolved. However, in recent studies some progress in understanding has been made. Changes in O-antigen structure mediated by lateral gene transfer, O-antigen conversion and phase variation, including fucosylation, glucosylation, acetylation and changes in O-antigen size, will be discussed. In addition to the observed LPS heterogeneity in bacterial pathogens, the structure of LPS is also altered in bacterial symbionts in response to signals from the plant during symbiosis. It appears to be part of a molecular communication between bacterium and host plant. Experiments ex planta suggest that the bacterium in the rhizosphere prepares its LPS for its roles in symbiosis by refining the LPS structure in response to seed and root compounds and the lower pH at the root surface. Moreover, modifications in LPS induced by conditions associated with infection are another indication that specific structures are important. Also during the differentiation from bacterium to bacteroid, the LPS of Rhizobium undergoes changes in the composition of the O-antigen, presumably in response to the change of environment. Recent findings suggest that, during symbiotic bacteroid development, reduced oxygen tension induces structural modifications in LPS that cause a switch from predominantly hydrophilic to predominantly hydrophobic molecular forms. However, the genetic mechanisms by which the LPS epitope changes are regulated remain unclear. Finally, the possible roles of O-antigen variations in symbiosis will be discussed.
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Affiliation(s)
- Inge Lerouge
- Centre of Microbial and Plant Genetics, Katholieke Universtiteit Leuven, Kasteelpark Arenberg 20, B-3001, Heverlee, Belgium
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25
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Affiliation(s)
- I R Henderson
- Center for Vaccine Development, Department of Pediatrics, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
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26
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Roche A, McFadden J, Owen P. Antigen 43, the major phase-variable protein of the Escherichia coli outer membrane, can exist as a family of proteins encoded by multiple alleles. MICROBIOLOGY (READING, ENGLAND) 2001; 147:161-9. [PMID: 11160810 DOI: 10.1099/00221287-147-1-161] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
agn43 encodes a major phase-variable outer-membrane protein, antigen 43 (Ag43), involved in autoaggregation of Escherichia coli cells. The gene is present in single copy on the chromosome of E. coli K-12. In contrast, Southern hybridization and gene inactivation studies demonstrate that control producer strain E. coli ML308-225 possesses duplicate copies of agn43 (agn43A and agn43B). Construction and analyses of single and double knockout mutants clearly show that both alleles are capable of expressing antigen in a phase-variable manner, with observed differences in the ON<-->OFF switch frequencies appearing to favour expression of Ag43B under conditions of normal laboratory growth. Comparative analysis of agn43A and agn43B gene sequences revealed 98% identity at the nucleotide and predicted protein levels, with differences in the protein sequence of the surface-expressed alpha(43) subunit altering the surface probability of one of the predicted epitopes. Analysis of a panel of enteropathogenic E. coli strains by Southern hybridization using agn43-specific gene probes provided strong evidence for the presence of varying numbers of agn43 alleles within clinical isolates. Taken together, the results indicate the presence of a family of distinct Ag43 proteins encoded by multiple chromosomal alleles.
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Affiliation(s)
- A Roche
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Ireland
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27
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Kjaergaard K, Schembri MA, Hasman H, Klemm P. Antigen 43 from Escherichia coli induces inter- and intraspecies cell aggregation and changes in colony morphology of Pseudomonas fluorescens. J Bacteriol 2000; 182:4789-96. [PMID: 10940019 PMCID: PMC111355 DOI: 10.1128/jb.182.17.4789-4796.2000] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Antigen 43 (Ag43) is a surface-displayed autotransporter protein of Escherichia coli. By virtue of its self-association characteristics, this protein is able to mediate autoaggregation and flocculation of E. coli cells in static cultures. Additionally, surface display of Ag43 is associated with a distinct frizzy colony morphology in E. coli. Here we show that Ag43 can be expressed in a functional form on the surface of the environmentally important Pseudomonas fluorescens strain SBW25 with ensuing cell aggregation and frizzy colony types. Using green fluorescence protein-tagged cells, we demonstrate that Ag43 can be used as a tool to provide interspecies cell aggregation between E. coli and P. fluorescens. Furthermore, Ag43 expression enhances biofilm formation in P. fluorescens to glass surfaces. The versatility of this protein was also reflected in Ag43 surface display in a variety of other gram-negative bacteria. Display of heterologous Ag43 in selected bacteria might offer opportunities for rational design of multispecies consortia where the concerted action of several bacterial species is required, e.g., waste treatment and degradation of pollutants.
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Affiliation(s)
- K Kjaergaard
- Department of Microbiology, Technical University of Denmark, DK-2800 Lyngby, Denmark
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28
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Haagmans W, van der Woude M. Phase variation of Ag43 in Escherichia coli: Dam-dependent methylation abrogates OxyR binding and OxyR-mediated repression of transcription. Mol Microbiol 2000; 35:877-87. [PMID: 10692164 DOI: 10.1046/j.1365-2958.2000.01762.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
It has been shown previously that phase variation of the outer membrane protein Antigen43 (Ag43) of Escherichia coli requires the DNA-methylating enzyme deoxyadenosine methyltransferase (Dam) and the global regulator OxyR. In this study, we analysed the regulation of the Ag43 encoding gene (agn) using isolates containing a fusion of the agn regulatory region to the reporter gene lacZ. Our results indicate that phase variation of Ag43 is regulated at the level of transcription. Repression of agn'-lacZ transcription required OxyR, whereas activation required Dam. The regulatory region of agn contains three GATC sequences, which are target sites for Dam-dependent methylation. In vivo, the methylation state of these GATC sequences correlated with the transcription state of agn'-lacZ. These GATC sequences were not protected from Dam-dependent methylation in an oxyR background, suggesting that OxyR binding results in Dam-dependent methylation protection in OFF cells. In vitro, both oxidized OxyR and OxyR(C199S), which is locked in the reduced conformation, bound to the agn regulatory region, but methylation of the three GATC sequences abrogated this binding. In vivo, OxyR(C199S) was sufficient to repress Ag43 transcription. Our data support a model in which OxyR-mediated repression of transcription is alleviated by methylation of three GATC sequences in its binding site. In addition, we show that, in an oxyR background, Dam was still required for full activation, suggesting that the model concerning the role of Dam in agn regulation is incomplete. These results show that Dam-dependent phase variation in E. coli is not limited to the previously identified regulatory system of the family of pap-like fimbrial operons.
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Affiliation(s)
- W Haagmans
- Department of Microbiology, University of Pennsylvania, 202A Johnson Pavilion, 3610 Hamilton Walk, Philadelphia, PA 19104, USA
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29
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Henderson IR, Czeczulin J, Eslava C, Noriega F, Nataro JP. Characterization of pic, a secreted protease of Shigella flexneri and enteroaggregative Escherichia coli. Infect Immun 1999; 67:5587-96. [PMID: 10531204 PMCID: PMC96930 DOI: 10.1128/iai.67.11.5587-5596.1999] [Citation(s) in RCA: 257] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have identified and characterized a secreted protein, designated Pic, which is encoded on the chromosomes of enteroaggregative Escherichia coli (EAEC) 042 and Shigella flexneri 2457T. The product of the pic gene is synthesized as a 146.5-kDa precursor molecule which is processed at the N and C termini during secretion, allowing the release of a mature protein (109.8 kDa) into the culture supernatant. The deduced amino acid sequence of Pic shows high homology to autotransporter proteins, particularly a subgroup termed the SPATEs (serine protease autotransporters of the Enterobacteriaceae). Present in all members of this subgroup is a motif similar to the active sites of certain serine proteases. Pic catalyzes gelatin degradation, which can be abolished by disruption of the predicted proteolytic active site. Functional analysis of the Pic protein implicates this factor in mucinase activity, serum resistance, and hemagglutination. Our data suggest that Pic may be a multifunctional protein involved in enteric pathogenesis.
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Affiliation(s)
- I R Henderson
- Center for Vaccine Development, Department of Pediatrics, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
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30
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Henderson IR, Hicks S, Navarro-Garcia F, Elias WP, Philips AD, Nataro JP. Involvement of the enteroaggregative Escherichia coli plasmid-encoded toxin in causing human intestinal damage. Infect Immun 1999; 67:5338-44. [PMID: 10496914 PMCID: PMC96889 DOI: 10.1128/iai.67.10.5338-5344.1999] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Enteroaggregative Escherichia coli (EAEC) strains have been shown to adhere to human intestinal tissue in an in vitro organ culture (IVOC) model, and certain strains manifest mucosal toxicity. We have recently described the EAEC plasmid-encoded toxin (Pet), a member of a specific serine protease subclass of the autotransporter proteins. When injected into rat ileal loops, Pet both elicited fluid accumulation and had cytotoxic effects on the mucosa. Furthermore, the Pet protein caused rises in short circuit current from rat jejunal tissue mounted in a Ussing chamber and rounding of intestinal epithelial cells in culture. We therefore hypothesized that the mucosal pathology induced by EAEC strains in the IVOC model was related to expression of the Pet protein. Here, we have examined the effects of EAEC strain 042 and its isogenic pet mutant in the IVOC model. 042-infected colonic explants exhibited dilation of crypt openings, increased cell rounding, development of prominent intercrypt crevices, and absence of apical mucus plugs. Colonic tissue incubated with the pet mutant exhibited significantly fewer mucosal abnormalities both subjectively and as quantitated morphometrically by measurement of crypt aperture diameter. Mucosal effects were restored upon complementation of the pet mutation in trans. Interestingly, we found that the ability of 042 to damage T84 cells was not dependent upon Pet. The data suggest that the Pet toxin is active on the human intestinal mucosa but that EAEC may have other mechanisms of eliciting mucosal damage.
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Affiliation(s)
- I R Henderson
- Center for Vaccine Development, Department of Pediatrics, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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31
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Hasman H, Chakraborty T, Klemm P. Antigen-43-mediated autoaggregation of Escherichia coli is blocked by fimbriation. J Bacteriol 1999; 181:4834-41. [PMID: 10438752 PMCID: PMC93969 DOI: 10.1128/jb.181.16.4834-4841.1999] [Citation(s) in RCA: 147] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Antigen 43 (Ag43), the product of the flu gene, is a surface-displayed autotransporter protein of Escherichia coli. Ag43 is responsible for the autoaggregation and flocculation of static liquid cultures of many E. coli strains. The expression of Ag43 has been reported to be phase variable and controlled by the product of the oxyR gene. Type 1 fimbriae are thin adhesive thread-like surface organelles responsible for bacterial receptor recognition and tissue colonization. Like that of Ag43, the expression of type 1 fimbriae is phase variable. Interestingly, previous results have suggested that the expression of type 1 fimbriae and the expression of Ag43 are mutually exclusive. In the present report, we show, by use of well-defined mutants, that fimbriation abolishes Ag43-mediated autoaggregation but does not affect Ag43 expression. Autoaggregation is shown to require an intercellular Ag43-Ag43 interaction, and the physical presence of fimbriae on the cells seems to abrogate this interaction. The Ag43 or OxyR status does not appear to influence fimbria expression, and our results suggest that the expression of Ag43 and the expression of fimbriae are independent processes.
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Affiliation(s)
- H Hasman
- Department of Microbiology, Technical University of Denmark, DK-2800 Lyngby, Denmark
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32
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Henderson IR, Owen P. The major phase-variable outer membrane protein of Escherichia coli structurally resembles the immunoglobulin A1 protease class of exported protein and is regulated by a novel mechanism involving Dam and oxyR. J Bacteriol 1999; 181:2132-41. [PMID: 10094691 PMCID: PMC93626 DOI: 10.1128/jb.181.7.2132-2141.1999] [Citation(s) in RCA: 122] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Here we report the characterization of an Escherichia coli gene (agn43) which encodes the principal phase-variable outer membrane protein termed antigen 43 (Ag43). The agn43 gene encodes a precursor protein of 107 kDa containing a 52-amino-acid signal sequence. Posttranslational processing generates an alpha43 subunit (predicted Mr of 49,789) and a C-terminal domain (beta43) with features typical of a bacterial integral outer membrane protein (predicted Mr of 51, 642). Secondary structure analysis predicts that beta43 exists as an 18-stranded beta barrel and that Ag43 shows structural organization closely resembling that of immunoglobulin A1 protease type of exoprotein produced by pathogenic Neisseria and Haemophilus spp. The correct processing of the polyprotein to alpha43 and beta43 in OmpT, OmpP, and DegP protease-deficient E. coli strains points to an autocatalytic cleavage mechanism, a hypothesis supported by the occurrence of an aspartyl protease active site within alpha43. Ag43, a species-specific antigen, possesses two RGD motifs of the type implicated in binding to human integrins. The mechanism of reversible phase variation was studied by immunochemical analysis of a panel of well-defined regulatory mutants and by analysis of DNA sequences upstream of agn43. Evidence strongly suggests that phase variation is regulated by both deoxyadenosine methylase (Dam) and by OxyR. Thus, oxyR mutants are locked on for Ag43 expression, whereas dam mutants are locked off for Ag43 expression. We propose a novel mechanism for the regulation of phase switching in which OxyR competes with Dam for unmethylated GATC sites in the regulatory region of the agn43 gene.
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MESH Headings
- Adhesins, Bacterial
- Adhesins, Escherichia coli
- Amino Acid Sequence
- Antigens, Bacterial/chemistry
- Antigens, Bacterial/genetics
- Antigens, Bacterial/metabolism
- Antigens, Surface/chemistry
- Antigens, Surface/genetics
- Antigens, Surface/metabolism
- Bacterial Outer Membrane Proteins/chemistry
- Bacterial Outer Membrane Proteins/genetics
- Bacterial Outer Membrane Proteins/metabolism
- Base Sequence
- DNA, Bacterial
- DNA-Binding Proteins
- Enterobacteriaceae/genetics
- Escherichia coli/genetics
- Escherichia coli/immunology
- Escherichia coli Proteins
- Immunoglobulin A/chemistry
- Immunoglobulin A/genetics
- Molecular Sequence Data
- Protein Processing, Post-Translational
- Protein Structure, Secondary
- Repressor Proteins/metabolism
- Sequence Homology, Amino Acid
- Site-Specific DNA-Methyltransferase (Adenine-Specific)/metabolism
- Transcription Factors/metabolism
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Affiliation(s)
- I R Henderson
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College Dublin, Dublin 2, Ireland
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Kwan LY, Isaacson RE. Identification and characterization of a phase-variable nonfimbrial Salmonella typhimurium gene that alters O-antigen production. Infect Immun 1998; 66:5725-30. [PMID: 9826347 PMCID: PMC108723 DOI: 10.1128/iai.66.12.5725-5730.1998] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Salmonella typhimurium 798, which was isolated from a pig, is known to phase vary from a nonadhesive to an adhesive phenotype. Cells of the adhesive phenotype adhere to porcine enterocytes, are more readily phagocytized by porcine neutrophils and macrophages, and once phagocytized can survive intracellularly, while cells of the nonadhesive phenotype die rapidly. The effect of phenotypic switching also can be visualized by changes in colony morphologies and the presence of between 10 and 15 proteins in the envelopes of cells in the adhesive phenotype. Mutants previously constructed with cells in the adhesive phenotype and the transposon TnphoA were screened to identify mutants lacking one or more of the unique proteins. One mutation was cloned and sequenced, and the mutation was shown to be in rfaL (O-antigen ligase). Expression of O antigen was shown to be phase variable. The adhesive strain expressed an O antigen that was at least eightfold longer than that for the nonadhesive strain and by virtue of O-antigen production was resistant to porcine complement. The mutant survived intracellularly in phagocytic cells as well as its wild-type parent.
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Affiliation(s)
- L Y Kwan
- Department of Veterinary Pathobiology, University of Illinois, Urbana, Illinois 61802, USA
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Eslava C, Navarro-García F, Czeczulin JR, Henderson IR, Cravioto A, Nataro JP. Pet, an autotransporter enterotoxin from enteroaggregative Escherichia coli. Infect Immun 1998; 66:3155-63. [PMID: 9632580 PMCID: PMC108327 DOI: 10.1128/iai.66.7.3155-3163.1998] [Citation(s) in RCA: 176] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/1998] [Accepted: 04/20/1998] [Indexed: 02/07/2023] Open
Abstract
Enteroaggregative Escherichia coli (EAEC) is an emerging cause of diarrheal illness. Clinical data suggest that diarrhea caused by EAEC is predominantly secretory in nature, but the responsible enterotoxin has not been described. Work from our laboratories has implicated a ca. 108-kDa protein as a heat-labile enterotoxin and cytotoxin, as evidenced by rises in short-circuit current and falls in tissue resistance in rat jejunal tissue mounted in an Ussing chamber. Here we report the genetic cloning, sequencing, and characterization of this high-molecular-weight heat-labile toxin. The toxin (designated the plasmid-encoded toxin [Pet]) is encoded on the 65-MDa adherence-related plasmid of EAEC strain 042. Nucleotide sequence analysis suggests that the toxin is a member of the autotransporter class of proteins, characterized by the presence of a conserved C-terminal domain which forms a beta-barrel pore in the bacterial outer membrane and through which the mature protein is transported. The Pet toxin is highly homologous to the EspP protease of enterohemorrhagic E. coli and to EspC of enteropathogenic E. coli, an as yet cryptic protein. In addition to its potential role in EAEC infection, Pet represents the first enterotoxin within the autotransporter class of secreted proteins. We hypothesize that other closely related members of this class may also produce enterotoxic effects.
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Affiliation(s)
- C Eslava
- Department of Public Health, Faculty of Medicine, UNAM, 04510 Mexico DF, Mexico.
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Henderson I, Owen P. The autoregulatory protein Mor and OxyR are identicial. MICROBIOLOGY (READING, ENGLAND) 1997; 143 ( Pt 5):1482. [PMID: 9229525 DOI: 10.1099/00221287-143-5-1482] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Henderson IR, Meehan M, Owen P. Antigen 43, a phase-variable bipartite outer membrane protein, determines colony morphology and autoaggregation in Escherichia coli K-12. FEMS Microbiol Lett 1997; 149:115-20. [PMID: 9103983 DOI: 10.1111/j.1574-6968.1997.tb10317.x] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The product controlling colony form variation and autoaggregation in Escherichia coli K-12 (the flu gene product) has been identified as the phase-variable, bipartite, outer membrane protein, termed antigen 43 (Ag43). Identification is based: (i) on complete correlation in authentic flu variants between colony morphology/autoaggregation and Ag43 expression as determined by colony and Western immunoblotting and immunofluorescence microscopy; and (ii) on the use of a specific probe to map the gene encoding Ag43 to a position (min 43) on the E. coli chromosome previously established for flu.
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Affiliation(s)
- I R Henderson
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College Dublin, Ireland
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Owen P, Meehan M, de Loughry-Doherty H, Henderson I. Phase-variable outer membrane proteins in Escherichia coli. FEMS IMMUNOLOGY AND MEDICAL MICROBIOLOGY 1996; 16:63-76. [PMID: 8988388 DOI: 10.1111/j.1574-695x.1996.tb00124.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Escherichia coli contains at least two phase-variable proteins in its outer membrane. One, termed antigen 43 (Ag43), is the product of the metastable flu gene located at min 43.6 on the E. coli chromosome and is responsible for colony form variation and for autoaggregation in liquid media. Ag43 is composed of two proteinaceous subunits, alpha 43 and beta 43 in 1:1 stoichiometry. alpha 43 (apparent M(r) 60,000) is surface expressed, extends beyond the O-side chains of smooth lipopolysaccharide and is bound to the cell surface through an interaction with beta 43 (apparent M(r) 53,000), itself an integral, heat-modifiable, outer membrane protein. alpha 43 shows limited N-terminal sequence homology with certain enterobacterial adhesins, and notable sequence homology with AIDA-1, an adhesin of diffuse-adhering E. coli. In addition, alpha 43 contains an RGD motif and a consensus sequence for an (autoproteolytic?) aspartyl protease active site. Expression of Ag43 is subject to reversible phase variation-in liquid minimal medium, the rates of variation from Ag43+ to Ag43- states and from Ag43- to Ag43+ states being approximately 2.2 x 10(-3) and approximately 1 x 10(-3), respectively. Phase switching of Ag43 is regulated by DNA methylation (deoxyadenosine methylase (dam) mutants being 'locked OFF') and by OxyR (oxyR mutants being 'locked ON'). It is proposed that OxyR acts as a repressor of Ag43 transcription by binding to unmethylated GATC sites in the regulatory region of the gene. In some strains, Ag43 may also undergo antigenic variation. A 94 kDa immunocrossreactive outer membrane protein, showing similar rates of phase variation, has additionally been detected for some enteropathogenic and uropathogenic strains of E. coli. This 94 kDa protein can be proteolytically cleaved in situ with trypsin to yield two membrane-bound products with M(r)s and properties similar to those of alpha 43 and beta 43. Results suggest that Ag43 may represent one of a family of antigenically-related high-M(r) adhesins which are synthesized as polyprotein precursors. Some members may be processed and presented on the cell surface as bipartite protein complexes (as Ag43). Others can remain uncleaved.
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Affiliation(s)
- P Owen
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College Dublin, Ireland
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