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Malik A, Kamli MR, Sabir JSM, Rather IA, Phan LT, Kim CB, Manavalan B. APLpred: A machine learning-based tool for accurate prediction and characterization of asparagine peptide lyases using sequence-derived optimal features. Methods 2024; 229:133-146. [PMID: 38944134 DOI: 10.1016/j.ymeth.2024.05.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2024] [Revised: 05/08/2024] [Accepted: 05/19/2024] [Indexed: 07/01/2024] Open
Abstract
Asparagine peptide lyase (APL) is among the seven groups of proteases, also known as proteolytic enzymes, which are classified according to their catalytic residue. APLs are synthesized as precursors or propeptides that undergo self-cleavage through autoproteolytic reaction. At present, APLs are grouped into 10 families belonging to six different clans of proteases. Recognizing their critical roles in many biological processes including virus maturation, and virulence, accurate identification and characterization of APLs is indispensable. Experimental identification and characterization of APLs is laborious and time-consuming. Here, we developed APLpred, a novel support vector machine (SVM) based predictor that can predict APLs from the primary sequences. APLpred was developed using Boruta-based optimal features derived from seven encodings and subsequently trained using five machine learning algorithms. After evaluating each model on an independent dataset, we selected APLpred (an SVM-based model) due to its consistent performance during cross-validation and independent evaluation. We anticipate APLpred will be an effective tool for identifying APLs. This could aid in designing inhibitors against these enzymes and exploring their functions. The APLpred web server is freely available at https://procarb.org/APLpred/.
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Affiliation(s)
- Adeel Malik
- Institute of Intelligence Informatics Technology, Sangmyung University, Seoul 03016, Republic of Korea
| | - Majid Rasool Kamli
- Department of Biological Sciences, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia
| | - Jamal S M Sabir
- Department of Biological Sciences, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia; Center of Excellence in Bionanoscience Research, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
| | - Irfan A Rather
- Department of Biological Sciences, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia; Center of Excellence in Bionanoscience Research, King Abdulaziz University, Jeddah 21589, Saudi Arabia
| | - Le Thi Phan
- Computational Biology and Bioinformatics Laboratory, Department of Integrative Biotechnology, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon 16419, Gyeonggi-do, Republic of Korea
| | - Chang-Bae Kim
- Department of Biotechnology, Sangmyung University, Seoul 03016, Republic of Korea.
| | - Balachandran Manavalan
- Computational Biology and Bioinformatics Laboratory, Department of Integrative Biotechnology, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon 16419, Gyeonggi-do, Republic of Korea.
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2
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Wang X, Nyenhuis SB, Bernstein HD. The translocation assembly module (TAM) catalyzes the assembly of bacterial outer membrane proteins in vitro. Nat Commun 2024; 15:7246. [PMID: 39174534 PMCID: PMC11341756 DOI: 10.1038/s41467-024-51628-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Accepted: 08/12/2024] [Indexed: 08/24/2024] Open
Abstract
The translocation and assembly module (TAM) has been proposed to play a crucial role in the assembly of a small subset of outer membrane proteins (OMPs) in Proteobacteria based on experiments conducted in vivo using tamA and tamB mutant strains and in vitro using biophysical methods. TAM consists of an OMP (TamA) and a periplasmic protein that is anchored to the inner membrane by a single α helix (TamB). Here we examine the function of the purified E. coli complex in vitro after reconstituting it into proteoliposomes. We find that TAM catalyzes the assembly of four model OMPs nearly as well as the β-barrel assembly machine (BAM), a universal heterooligomer that contains a TamA homolog (BamA) and that catalyzes the assembly of almost all E. coli OMPs. Consistent with previous results, both TamA and TamB are required for significant TAM activity. Our study provides direct evidence that TAM can function as an independent OMP insertase and describes a new method to gain insights into TAM function.
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Affiliation(s)
- Xu Wang
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Sarah B Nyenhuis
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Harris D Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA.
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3
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Abuta'a YA, Caumont-Sarcos A, Albenne C, Ieva R. In Vivo Site-Directed and Time-Resolved Photocrosslinking of Envelope Proteins. Methods Mol Biol 2024; 2715:299-320. [PMID: 37930537 DOI: 10.1007/978-1-0716-3445-5_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2023]
Abstract
In vivo site-directed photocrosslinking provides a means to probe the vicinity of proteins in their native cellular environment. Because this method relies on the incorporation of unnatural amino acid analogs that are similar in size to natural amino acids, crosslink products are indicative of direct protein-protein interactions. Here, we present the use of this approach to monitor both transient and stable interactions of two proteins of the envelope of Escherichia coli. First, we describe a protocol to characterize the interactions of a secretory protein as it transverses the bacterial envelope with temporal and spatial resolution. We combine site-directed photocrosslinking with radiolabeling of proteins and lipids. Second, we describe a method to purify a photocrosslinked partner protein and to analyze it by mass spectrometry. We use in-gel protein digestion and peptide fragmentation by MALDI-TOF/TOF tandem mass spectrometry to determine the site of interaction on the photocrosslinked partner.
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Affiliation(s)
- Yassin A Abuta'a
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Anne Caumont-Sarcos
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Cécile Albenne
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Raffaele Ieva
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France.
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4
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Jarzab M, Skorko-Glonek J. There Are No Insurmountable Barriers: Passage of the Helicobacter pylori VacA Toxin from Bacterial Cytoplasm to Eukaryotic Cell Organelle. MEMBRANES 2023; 14:11. [PMID: 38248700 PMCID: PMC10821523 DOI: 10.3390/membranes14010011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 12/20/2023] [Accepted: 12/23/2023] [Indexed: 01/23/2024]
Abstract
The Gram-negative bacterium Helicobacter pylori is a very successful pathogen, one of the most commonly identified causes of bacterial infections in humans worldwide. H. pylori produces several virulence factors that contribute to its persistence in the hostile host habitat and to its pathogenicity. The most extensively studied are cytotoxin-associated gene A (CagA) and vacuolating cytotoxin A (VacA). VacA is present in almost all H. pylori strains. As a secreted multifunctional toxin, it assists bacterial colonization, survival, and proliferation during long-lasting infections. To exert its effect on gastric epithelium and other cell types, VacA undergoes several modifications and crosses multiple membrane barriers. Once inside the gastric epithelial cell, VacA disrupts many cellular-signaling pathways and processes, leading mainly to changes in the efflux of various ions, the depolarization of membrane potential, and perturbations in endocytic trafficking and mitochondrial function. The most notable effect of VacA is the formation of vacuole-like structures, which may lead to apoptosis. This review focuses on the processes involved in VacA secretion, processing, and entry into host cells, with a particular emphasis on the interaction of the mature toxin with host membranes and the formation of transmembrane pores.
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Affiliation(s)
| | - Joanna Skorko-Glonek
- Department of General and Medical Biochemistry, Faculty of Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland;
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Abstract
Several antibacterial compounds have recently been discovered that potentially inhibit the activity of BamA, an essential subunit of a heterooligomer (the barrel assembly machinery or BAM) that assembles outer membrane proteins (OMPs) in Gram-negative bacteria, but their mode of action is unclear. To address this issue, we examined the effect of three inhibitors on the biogenesis of a model E. coli OMP (EspP) in vivo. We found that darobactin potently inhibited the interaction of a conserved C-terminal sequence motif (the “β signal”) with BamA, but had no effect on assembly if added at a postbinding stage. In contrast, Polyphor peptide 7 and MRL-494 inhibited both binding and at least one later step of assembly. Taken together with previous studies that analyzed the binding of darobactin and Polyphor peptide 7 to BamA in vitro, our results strongly suggest that the two compounds inhibit BAM function by distinct competitive and allosteric mechanisms. In addition to providing insights into the properties of the antibacterial compounds, our results also provide direct experimental evidence that supports a model in which the binding of the β signal to BamA initiates the membrane insertion of OMPs.
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6
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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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Doyle MT, Jimah JR, Dowdy T, Ohlemacher SI, Larion M, Hinshaw JE, Bernstein HD. Cryo-EM structures reveal multiple stages of bacterial outer membrane protein folding. Cell 2022; 185:1143-1156.e13. [PMID: 35294859 DOI: 10.1016/j.cell.2022.02.016] [Citation(s) in RCA: 41] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 12/01/2021] [Accepted: 02/13/2022] [Indexed: 02/08/2023]
Abstract
Transmembrane β barrel proteins are folded into the outer membrane (OM) of Gram-negative bacteria by the β barrel assembly machinery (BAM) via a poorly understood process that occurs without known external energy sources. Here, we used single-particle cryo-EM to visualize the folding dynamics of a model β barrel protein (EspP) by BAM. We found that BAM binds the highly conserved "β signal" motif of EspP to correctly orient β strands in the OM during folding. We also found that the folding of EspP proceeds via "hybrid-barrel" intermediates in which membrane integrated β sheets are attached to the essential BAM subunit, BamA. The structures show an unprecedented deflection of the membrane surrounding the EspP intermediates and suggest that β sheets progressively fold toward BamA to form a β barrel. Along with in vivo experiments that tracked β barrel folding while the OM tension was modified, our results support a model in which BAM harnesses OM elasticity to accelerate β barrel folding.
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Affiliation(s)
- Matthew Thomas Doyle
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - John R Jimah
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Tyrone Dowdy
- Neuro-Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Shannon I Ohlemacher
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Mioara Larion
- Neuro-Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jenny E Hinshaw
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Harris D Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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8
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Hermansen S, Linke D, Leo JC. Transmembrane β-barrel proteins of bacteria: From structure to function. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2022; 128:113-161. [PMID: 35034717 DOI: 10.1016/bs.apcsb.2021.07.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The outer membrane of Gram-negative bacteria is a specialized organelle conferring protection to the cell against various environmental stresses and resistance to many harmful compounds. The outer membrane has a number of unique features, including an asymmetric lipid bilayer, the presence of lipopolysaccharides and an individual proteome. The vast majority of the integral transmembrane proteins in the outer membrane belongs to the family of β-barrel proteins. These evolutionarily related proteins share a cylindrical, anti-parallel β-sheet core fold spanning the outer membrane. The loops and accessory domains attached to the β-barrel allow for a remarkable versatility in function for these proteins, ranging from diffusion pores and transporters to enzymes and adhesins. We summarize the current knowledge on β-barrel structure and folding and give an overview of their functions, evolution, and potential as drug targets.
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Affiliation(s)
- Simen Hermansen
- Section for Genetics and Evolutionary Biology, Department of Biosciences, University of Oslo, Oslo, Norway
| | - Dirk Linke
- Section for Genetics and Evolutionary Biology, Department of Biosciences, University of Oslo, Oslo, Norway
| | - Jack C Leo
- Antimicrobial resistance, Omics and Microbiota Group, Department of Biosciences, Nottingham Trent University, Nottingham, United Kingdom.
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9
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Doyle MT, Bernstein HD. BamA forms a translocation channel for polypeptide export across the bacterial outer membrane. Mol Cell 2021; 81:2000-2012.e3. [PMID: 33705710 DOI: 10.1016/j.molcel.2021.02.023] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 01/05/2021] [Accepted: 02/18/2021] [Indexed: 12/18/2022]
Abstract
The β-barrel assembly machine (BAM) integrates β-barrel proteins into the outer membrane (OM) of Gram-negative bacteria. An essential BAM subunit (BamA) catalyzes integration by promoting the formation of a hybrid-barrel intermediate state between its own β-barrel domain and that of its client proteins. Here we show that in addition to catalyzing the integration of β-barrel proteins, BamA functions as a polypeptide export channel. In vivo structural mapping via intermolecular disulfide crosslinking showed that the extracellular "passenger" domain of a member of the "autotransporter" superfamily of virulence factors traverses the OM through the BamA β-barrel lumen. Furthermore, we demonstrate that a highly conserved residue within autotransporter β-barrels is required to position the passenger inside BamA to initiate translocation and that during translocation, the passenger stabilizes the hybrid-barrel state. Our results not only establish a new function for BamA but also unify the divergent functions of BamA and other "Omp85" superfamily transporters.
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Affiliation(s)
- Matthew Thomas Doyle
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Harris David Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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10
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Bam complex-mediated assembly of bacterial outer membrane proteins synthesized in an in vitro translation system. Sci Rep 2020; 10:4557. [PMID: 32165713 PMCID: PMC7067875 DOI: 10.1038/s41598-020-61431-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Accepted: 02/21/2020] [Indexed: 02/01/2023] Open
Abstract
Bacterial outer membrane proteins (OMPs) contain a unique "β barrel" segment that is inserted into the membrane by the barrel assembly machinery (Bam) complex by an unknown mechanism. OMP assembly has been reconstituted in vitro, but assembly reactions have involved the use of urea-denatured protein purified from inclusion bodies. Here we show that the E. coli Bam complex catalyzes the efficient assembly of OMPs synthesized de novo in a coupled in vitro transcription/translation system. Interestingly, the in vitro translated forms of the OMPs we analyzed were assembled more rapidly and were effectively engaged by fewer periplasmic chaperones than their urea-denatured counterparts. Taken together, our results strongly suggest that the mode of production influences the conformational states sampled by OMPs and thereby affects their recognition by both chaperones and the Bam complex. Besides providing insights into OMP biogenesis, our work describes a novel, streamlined method to reconstitute OMP assembly in vitro.
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11
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Ryoo D, Rydmark MO, Pang YT, Lundquist KP, Linke D, Gumbart JC. BamA is required for autotransporter secretion. Biochim Biophys Acta Gen Subj 2020; 1864:129581. [PMID: 32114025 DOI: 10.1016/j.bbagen.2020.129581] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2019] [Revised: 02/01/2020] [Accepted: 02/22/2020] [Indexed: 01/24/2023]
Abstract
BACKGROUND In Gram-negative bacteria, type Va and Vc autotransporters are proteins that contain both a secreted virulence factor (the "passenger" domain) and a β-barrel that aids its export. While it is known that the folding and insertion of the β-barrel domain utilize the β-barrel assembly machinery (BAM) complex, how the passenger domain is secreted and folded across the membrane remains to be determined. The hairpin model states that passenger domain secretion occurs independently through the fully-formed and membrane-inserted β-barrel domain via a hairpin folding intermediate. In contrast, the BamA-assisted model states that the passenger domain is secreted through a hybrid of BamA, the essential subunit of the BAM complex, and the β-barrel domain of the autotransporter. METHODS To ascertain the models' plausibility, we have used molecular dynamics to simulate passenger domain secretion for two autotransporters, EspP and YadA. RESULTS We observed that each protein's β-barrel is unable to accommodate the secreting passenger domain in a hairpin configuration without major structural distortions. Additionally, the force required for secretion through EspP's β-barrel is more than that through the BamA β-barrel. CONCLUSIONS Secretion of autotransporters most likely occurs through an incompletely formed β-barrel domain of the autotransporter in conjunction with BamA. GENERAL SIGNIFICANCE Secretion of virulence factors is a process used by practically all pathogenic Gram-negative bacteria. Understanding this process is a necessary step towards limiting their infectious capacity.
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Affiliation(s)
- David Ryoo
- Interdisciplinary Bioengineering Graduate Program, Georgia Institute of Technology, Atlanta, GA 30332, United States of America
| | | | - Yui Tik Pang
- School of Physics, Georgia Institute of Technology, Atlanta, GA 30313, United States of America
| | - Karl P Lundquist
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, United States of America
| | - Dirk Linke
- Department of Biosciences, University of Oslo, Oslo, Norway
| | - James C Gumbart
- School of Physics, Georgia Institute of Technology, Atlanta, GA 30313, United States of America.
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12
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Pokharel P, Habouria H, Bessaiah H, Dozois CM. Serine Protease Autotransporters of the Enterobacteriaceae (SPATEs): Out and About and Chopping It Up. Microorganisms 2019; 7:E594. [PMID: 31766493 PMCID: PMC6956023 DOI: 10.3390/microorganisms7120594] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 11/13/2019] [Indexed: 02/06/2023] Open
Abstract
Autotransporters are secreted proteins with multiple functions produced by a variety of Gram-negative bacteria. In Enterobacteriaceae, a subgroup of these autotransporters are the SPATEs (serine protease autotransporters of Enterobacteriaceae). SPATEs play a crucial role in survival and virulence of pathogens such as Escherichia coli and Shigella spp. and contribute to intestinal and extra-intestinal infections. These high molecular weight proteases are transported to the external milieu by the type Va secretion system and function as proteases with diverse substrate specificities and biological functions including adherence and cytotoxicity. Herein, we provide an overview of SPATEs and discuss recent findings on the biological roles of these secreted proteins, including proteolysis of substrates, adherence to cells, modulation of the immune response, and virulence in host models. In closing, we highlight recent insights into the regulation of expression of SPATEs that could be exploited to understand fundamental SPATE biology.
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Affiliation(s)
- Pravil Pokharel
- Institut National de Recherche Scientifique (INRS)-Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada; (P.P.); (H.H.); (H.B.)
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Saint-Hyacinthe, QC J2S 2M2, Canada
| | - Hajer Habouria
- Institut National de Recherche Scientifique (INRS)-Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada; (P.P.); (H.H.); (H.B.)
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Saint-Hyacinthe, QC J2S 2M2, Canada
| | - Hicham Bessaiah
- Institut National de Recherche Scientifique (INRS)-Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada; (P.P.); (H.H.); (H.B.)
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Saint-Hyacinthe, QC J2S 2M2, Canada
| | - Charles M. Dozois
- Institut National de Recherche Scientifique (INRS)-Centre Armand-Frappier Santé Biotechnologie, Laval, QC H7V 1B7, Canada; (P.P.); (H.H.); (H.B.)
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Saint-Hyacinthe, QC J2S 2M2, Canada
- Institut Pasteur International Network, Laval, QC H7V 1B7, Canada
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13
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Sanchez-Villamil JI, Navarro-Garcia F, Castillo-Romero A, Gutierrez-Gutierrez F, Tapia D, Tapia-Pastrana G. Curcumin Blocks Cytotoxicity of Enteroaggregative and Enteropathogenic Escherichia coli by Blocking Pet and EspC Proteolytic Release From Bacterial Outer Membrane. Front Cell Infect Microbiol 2019; 9:334. [PMID: 31681620 PMCID: PMC6798032 DOI: 10.3389/fcimb.2019.00334] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 09/11/2019] [Indexed: 01/14/2023] Open
Abstract
Pet and EspC are toxins secreted by enteroaggregative (EAEC) and enteropathogenic (EPEC) diarrheagenic Escherichia coli pathotypes, respectively. Both toxins are members of the Serine Protease Autotransporters of Enterobacteriaceae (SPATEs) family. Pet and EspC are important virulence factors that produce cytotoxic and enterotoxic effects on enterocytes. Here, we evaluated the effect of curcumin, a polyphenolic compound obtained from the rhizomes of Curcuma longa L. (Zingiberaceae) on the secretion and cytotoxic effects of Pet and EspC proteins. We found that curcumin prevents Pet and EspC secretion without affecting bacterial growth or the expression of pet and espC. Our results show that curcumin affects the release of these SPATEs from the translocation domain, thereby affecting the pathogenesis of EAEC and EPEC. Curcumin-treated EAEC and EPEC did not induce significant cell damage like the ability to disrupt the actin cytoskeleton, without affecting their characteristic adherence patterns on epithelial cells. A molecular model of docking predicted that curcumin interacts with the determinant residues Asp1018-Asp1019 and Asp1029-Asp1030 of the translocation domain required for the release of Pet and EspC, respectively. Consequently, curcumin blocks Pet and EspC cytotoxicity on epithelial cells by preventing their release from the outer membrane.
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Affiliation(s)
- Javier I Sanchez-Villamil
- Department of Cell Biology, Centro de Investigación y de Estudios Avanzados del IPN (CINVESTAV-IPN), Mexico City, Mexico
| | - Fernando Navarro-Garcia
- Department of Cell Biology, Centro de Investigación y de Estudios Avanzados del IPN (CINVESTAV-IPN), Mexico City, Mexico
| | - Araceli Castillo-Romero
- Department of Microbiology and Pathology, Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, Guadalajara, Mexico
| | - Filiberto Gutierrez-Gutierrez
- Department of Chemistry, Centro Universitario de Ciencias Exactas e Ingenierías, Universidad de Guadalajara, Guadalajara, Mexico
| | - Daniel Tapia
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, United States
| | - Gabriela Tapia-Pastrana
- Laboratory of Biomedical Investigation, Hospital Regional de Alta Especialidad de Oaxaca, San Bartolo Coyotepec, Mexico
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14
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Meuskens I, Saragliadis A, Leo JC, Linke D. Type V Secretion Systems: An Overview of Passenger Domain Functions. Front Microbiol 2019; 10:1163. [PMID: 31214135 PMCID: PMC6555100 DOI: 10.3389/fmicb.2019.01163] [Citation(s) in RCA: 98] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Accepted: 05/07/2019] [Indexed: 12/12/2022] Open
Abstract
Bacteria secrete proteins for different purposes such as communication, virulence functions, adhesion to surfaces, nutrient acquisition, or growth inhibition of competing bacteria. For secretion of proteins, Gram-negative bacteria have evolved different secretion systems, classified as secretion systems I through IX to date. While some of these systems consist of multiple proteins building a complex spanning the cell envelope, the type V secretion system, the subject of this review, is rather minimal. Proteins of the Type V secretion system are often called autotransporters (ATs). In the simplest case, a type V secretion system consists of only one polypeptide chain with a β-barrel translocator domain in the membrane, and an extracellular passenger or effector region. Depending on the exact domain architecture of the protein, type V secretion systems can be further separated into sub-groups termed type Va through e, and possibly another recently identified subtype termed Vf. While this classification works well when it comes to the architecture of the proteins, this is not the case for the function(s) of the secreted passenger. In this review, we will give an overview of the functions of the passengers of the different AT classes, shedding more light on the variety of functions carried out by type V secretion systems.
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Affiliation(s)
| | | | | | - Dirk Linke
- Department of Biosciences, Section for Genetics and Evolutionary Biology, University of Oslo, Oslo, Norway
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15
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Peterson JH, Hussain S, Bernstein HD. Identification of a novel post-insertion step in the assembly of a bacterial outer membrane protein. Mol Microbiol 2018; 110:143-159. [PMID: 30107065 DOI: 10.1111/mmi.14102] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/07/2018] [Indexed: 01/09/2023]
Abstract
Although the barrel assembly machinery (Bam) complex has been shown to facilitate the insertion of β barrel proteins into the bacterial outer membrane (OM), the stage at which β barrels fold is unknown. Here, we describe insights into β barrel assembly that emerged from an analysis of a member of the autotransporter family of OM proteins (EspP) in Escherichia coli. EspP contains an extracellular 'passenger' domain that is translocated across the OM and then released from the covalently linked β barrel domain in an intra-barrel cleavage reaction. We found that the mutation of an unusual lipid-exposed lysine residue impairs a previously unidentified late folding step that follows both the membrane insertion of the β barrel domain and the secretion of the passenger domain but that precedes proteolytic maturation. Our results demonstrate that β barrel assembly can be completed at a post-insertion stage and raise the possibility that interactions with membrane lipids can promote folding in vivo. Furthermore, by showing that the passenger domain is secreted before the β barrel domain is fully assembled, our results also provide evidence against the long-standing hypothesis that autotransporters are autonomous protein secretion systems.
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Affiliation(s)
- Janine H Peterson
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892-0538, USA
| | - Sunyia Hussain
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892-0538, USA
| | - Harris D Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892-0538, USA
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16
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van Ulsen P, Zinner KM, Jong WSP, Luirink J. On display: autotransporter secretion and application. FEMS Microbiol Lett 2018; 365:5061625. [DOI: 10.1093/femsle/fny165] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 07/27/2018] [Indexed: 12/12/2022] Open
Affiliation(s)
- Peter van Ulsen
- Section Molecular Microbiology, Department of Molecular Cell Biology, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), Vrije Universiteit, 1081 HV Amsterdam, The Netherlands
| | - Katinka M Zinner
- Section Molecular Microbiology, Department of Molecular Cell Biology, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), Vrije Universiteit, 1081 HV Amsterdam, The Netherlands
| | | | - Joen Luirink
- Section Molecular Microbiology, Department of Molecular Cell Biology, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), Vrije Universiteit, 1081 HV Amsterdam, The Netherlands
- Abera Bioscience AB, SE-111 45 Stockholm, Sweden
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17
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Raeven RH, Brummelman J, Pennings JLA, van der Maas L, Helm K, Tilstra W, van der Ark A, Sloots A, van der Ley P, van Eden W, Jiskoot W, van Riet E, van Els CA, Kersten GF, Han WG, Metz B. Molecular and cellular signatures underlying superior immunity against Bordetella pertussis upon pulmonary vaccination. Mucosal Immunol 2018; 11:979-993. [PMID: 28930286 DOI: 10.1038/mi.2017.81] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 08/15/2017] [Indexed: 02/04/2023]
Abstract
Mucosal immunity is often required for protection against respiratory pathogens but the underlying cellular and molecular mechanisms of induction remain poorly understood. Here, systems vaccinology was used to identify immune signatures after pulmonary or subcutaneous immunization of mice with pertussis outer membrane vesicles. Pulmonary immunization led to improved protection, exclusively induced mucosal immunoglobulin A (IgA) and T helper type 17 (Th17) responses, and in addition evoked elevated systemic immunoglobulin G (IgG) antibody levels, IgG-producing plasma cells, memory B cells, and Th17 cells. These adaptive responses were preceded by unique local expression of genes of the innate immune response related to Th17 (e.g., Rorc) and IgA responses (e.g., Pigr) in addition to local and systemic secretion of Th1/Th17-promoting cytokines. This comprehensive systems approach identifies the effect of the administration route on the development of mucosal immunity, its importance in protection against Bordetella pertussis, and reveals potential molecular correlates of vaccine immunity to this reemerging pathogen.
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Affiliation(s)
- R Hm Raeven
- Institute for Translational Vaccinology (Intravacc), Bilthoven, The Netherlands.,Division of Drug Delivery Technology, Cluster BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden, The Netherlands
| | - J Brummelman
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.,Department of Infectious Diseases and Immunology, Utrecht University, Utrecht, The Netherlands
| | - J L A Pennings
- Centre for Health Protection, National Institute for Public Health and the Environment, Bilthoven, The Netherlands
| | - L van der Maas
- Institute for Translational Vaccinology (Intravacc), Bilthoven, The Netherlands
| | - K Helm
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands
| | - W Tilstra
- Institute for Translational Vaccinology (Intravacc), Bilthoven, The Netherlands
| | - A van der Ark
- Institute for Translational Vaccinology (Intravacc), Bilthoven, The Netherlands
| | - A Sloots
- Institute for Translational Vaccinology (Intravacc), Bilthoven, The Netherlands
| | - P van der Ley
- Institute for Translational Vaccinology (Intravacc), Bilthoven, The Netherlands
| | - W van Eden
- Department of Infectious Diseases and Immunology, Utrecht University, Utrecht, The Netherlands
| | - W Jiskoot
- Division of Drug Delivery Technology, Cluster BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden, The Netherlands
| | - E van Riet
- Institute for Translational Vaccinology (Intravacc), Bilthoven, The Netherlands
| | - C Acm van Els
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands
| | - G Fa Kersten
- Institute for Translational Vaccinology (Intravacc), Bilthoven, The Netherlands.,Division of Drug Delivery Technology, Cluster BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden, The Netherlands
| | - W Gh Han
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands
| | - B Metz
- Institute for Translational Vaccinology (Intravacc), Bilthoven, The Netherlands
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18
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Molecular basis for the folding of β-helical autotransporter passenger domains. Nat Commun 2018; 9:1395. [PMID: 29643377 PMCID: PMC5895577 DOI: 10.1038/s41467-018-03593-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 02/27/2018] [Indexed: 11/23/2022] Open
Abstract
Bacterial autotransporters comprise a C-terminal β-barrel domain, which must be correctly folded and inserted into the outer membrane to facilitate translocation of the N-terminal passenger domain to the cell exterior. Once at the surface, the passenger domains of most autotransporters are folded into an elongated β-helix. In a cellular context, key molecules catalyze the assembly of the autotransporter β-barrel domain. However, how the passenger domain folds into its functional form is poorly understood. Here we use mutational analysis on the autotransporter Pet to show that the β-hairpin structure of the fifth extracellular loop of the β-barrel domain has a crucial role for passenger domain folding into a β-helix. Bioinformatics and structural analyses, and mutagenesis of a homologous autotransporter, suggest that this function is conserved among autotransporter proteins with β-helical passenger domains. We propose that the autotransporter β-barrel domain is a folding vector that nucleates folding of the passenger domain. Autotransporter passenger domains are presented on or released from the bacterial surface upon translocation through an outer membrane β-barrel anchor. Here the authors study the two E. coli autotransporters Pet and EspP and propose that the β-barrel anchor acts as a vector to nucleate the folding of the passenger domain.
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19
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Hussain S, Bernstein HD. The Bam complex catalyzes efficient insertion of bacterial outer membrane proteins into membrane vesicles of variable lipid composition. J Biol Chem 2018; 293:2959-2973. [PMID: 29311257 DOI: 10.1074/jbc.ra117.000349] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 12/06/2017] [Indexed: 12/29/2022] Open
Abstract
Most proteins that reside in the bacterial outer membrane (OM) have a distinctive "β-barrel" architecture, but the assembly of these proteins is poorly understood. The spontaneous assembly of OM proteins (OMPs) into pure lipid vesicles has been studied extensively but often requires non-physiological conditions and time scales and is strongly influenced by properties of the lipid bilayer, including surface charge, thickness, and fluidity. Furthermore, the membrane insertion of OMPs in vivo is catalyzed by a heterooligomer called the β-barrel assembly machinery (Bam) complex. To determine the role of lipids in the assembly of OMPs under more physiological conditions, we exploited an assay in which the Bam complex mediates their insertion into membrane vesicles. After reconstituting the Bam complex into vesicles that contain a variety of different synthetic lipids, we found that two model OMPs, EspP and OmpA, folded efficiently regardless of the lipid composition. Most notably, both proteins folded into membranes composed of a gel-phase lipid that mimics the rigid bacterial OM. Interestingly, we found that EspP, OmpA, and another model protein (OmpG) folded at significantly different rates and that an α-helix embedded inside the EspP β-barrel accelerates folding. Our results show that the Bam complex largely overcomes effects that lipids exert on OMP assembly and suggest that specific interactions between the Bam complex and an OMP influence its rate of folding.
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Affiliation(s)
- Sunyia Hussain
- Genetics and Biochemistry Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892-0538
| | - Harris D Bernstein
- Genetics and Biochemistry Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892-0538.
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20
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Friedrich L, Kornberger P, Mendler CT, Multhoff G, Schwaiger M, Skerra A. Selection of an Anticalin® against the membrane form of Hsp70 via bacterial surface display and its theranostic application in tumour models. Biol Chem 2017; 399:235-252. [DOI: 10.1515/hsz-2017-0207] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 10/23/2017] [Indexed: 01/08/2023]
Abstract
Abstract
We describe the selection of Anticalins against a common tumour surface antigen, human Hsp70, using functional display on live Escherichia coli cells as fusion with a truncated EspP autotransporter. While found intracellularly in normal cells, Hsp70 is frequently exposed in a membrane-bound state on the surface of tumour cells and, even more pronounced, in metastases or after radiochemotherapy. Employing a recombinant Hsp70 fragment comprising residues 383-548 as the target, Anticalins were selected from a naïve bacterial library. The Anticalin with the highest affinity (K
D=13 nm), as determined towards recombinant full-length Hsp70 by real-time surface plasmon resonance analysis, was improved to K
D=510 pm by doped random mutagenesis and another cycle of E. coli surface display, followed by rational combination of mutations. This Anticalin, which recognises a linear peptide epitope located in the interdomain linker of Hsp70, was demonstrated to specifically bind Hsp70 in its membrane-associated form in immunofluorescence microscopy and via flow cytometry using the FaDu cell line, which is positive for surface Hsp70. The radiolabelled and PASylated Anticalin revealed specific tumour accumulation in xenograft mice using positron emission tomography (PET) imaging. Furthermore, after enzymatic coupling to the protein toxin gelonin, the Anticalin showed potent cytotoxicity on FaDu cells in vitro.
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Affiliation(s)
- Lars Friedrich
- Munich Center for Integrated Protein Science, CIPS-M, and Lehrstuhl für Biologische Chemie , Technische Universität München , D-85354 Freising (Weihenstephan) , Germany
| | - Petra Kornberger
- Munich Center for Integrated Protein Science, CIPS-M, and Lehrstuhl für Biologische Chemie , Technische Universität München , D-85354 Freising (Weihenstephan) , Germany
| | - Claudia T. Mendler
- Munich Center for Integrated Protein Science, CIPS-M, and Lehrstuhl für Biologische Chemie , Technische Universität München , D-85354 Freising (Weihenstephan) , Germany
| | - Gabriele Multhoff
- Department of Radiation Oncology , Klinikum rechts der Isar, Technische Universität München , D-81675 München , Germany
| | - Markus Schwaiger
- Department of Nuclear Medicine, Klinikum rechts der Isar , Technische Universität München , D-81675 München , Germany
| | - Arne Skerra
- Munich Center for Integrated Protein Science, CIPS-M, and Lehrstuhl für Biologische Chemie , Technische Universität München , D-85354 Freising (Weihenstephan) , Germany
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21
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Peterson JH, Plummer AM, Fleming KG, Bernstein HD. Selective pressure for rapid membrane integration constrains the sequence of bacterial outer membrane proteins. Mol Microbiol 2017; 106:777-792. [PMID: 28941249 DOI: 10.1111/mmi.13845] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/19/2017] [Indexed: 12/11/2022]
Abstract
Almost all bacterial outer membrane proteins (OMPs) contain a β barrel domain that serves as a membrane anchor, but the assembly and quality control of these proteins are poorly understood. Here, we show that the introduction of a single lipid-facing arginine residue near the middle of the β barrel of the Escherichia coli OMPs OmpLA and EspP creates an energy barrier that impedes membrane insertion. Although several unintegrated OmpLA mutants remained insertion-competent, they were slowly degraded by the periplasmic protease DegP. Two EspP mutants were also gradually degraded by DegP but were toxic because they first bound to the Bam complex, an essential heteroligomer that catalyzes the membrane insertion of OMPs. Interestingly, another EspP mutant likewise formed a prolonged, deleterious interaction with the Bam complex but was protected from degradation and eventually inserted into the membrane in a native conformation. The different types of interactions between the EspP mutants and the Bam complex that we observed may correspond to distinct stages in OMP assembly. Our results show that sequences that significantly delay assembly are disfavored not only because unintegrated OMPs are subjected to degradation, but also because OMPs that assemble slowly can form dominant-negative interactions with the Bam complex.
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Affiliation(s)
- Janine H Peterson
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases National Institutes of Health, Bethesda, MD 20892, USA
| | - Ashlee M Plummer
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
| | - Karen G Fleming
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
| | - Harris D Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases National Institutes of Health, Bethesda, MD 20892, USA
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22
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Albenne C, Ieva R. Job contenders: roles of the β-barrel assembly machinery and the translocation and assembly module in autotransporter secretion. Mol Microbiol 2017; 106:505-517. [PMID: 28887826 DOI: 10.1111/mmi.13832] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/07/2017] [Indexed: 01/17/2023]
Abstract
In Gram-negative bacteria, autotransporters secrete effector protein domains that are linked to virulence. Although they were once thought to be simple and autonomous secretion machines, mounting evidence reveals that multiple factors of the bacterial envelope are necessary for autotransporter assembly. Secretion across the outer membrane of their soluble effector "passenger domain" is promoted by the assembly of an outer membrane-spanning "β-barrel domain". Both reactions require BamA, an essential component of the β-barrel assembly machinery (BAM complex) that catalyzes the final reaction step by which outer membrane proteins are integrated into the lipid bilayer. A large amount of data generated in the last decade has shed key insights onto the mechanistic coordination of autotransporter β-barrel domain assembly and passenger domain secretion. These results, together with the recently solved structures of the BAM complex, offer an unprecedented opportunity to discuss a detailed model of autotransporter assembly. Importantly, some autotransporters benefit from the presence of an additional machinery, the translocation and assembly module (TAM), a two-membrane spanning complex, which contains a BamA-homologous subunit. Although it remains unclear how the BAM complex and the TAM cooperate, it is evident that multiple preparatory steps are necessary for efficient autotransporter biogenesis.
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Affiliation(s)
- Cécile Albenne
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Raffaele Ieva
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
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23
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Ieva R. Site-Directed and Time-Resolved Photocrosslinking in Cells Metabolically Labeled with Radioisotopes. Methods Mol Biol 2017; 1615:233-245. [PMID: 28667617 DOI: 10.1007/978-1-4939-7033-9_19] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
To efficiently transport proteins into and across cellular membranes, specialized transport machineries engage in recognition events with different domains of their client proteins, forming sequential intermediate complexes. The short-lived nature of these interactions poses a big challenge in the identification of the key factors involved in transport reactions and their mechanism of action. Site-directed photocrosslinking is a powerful method for the detection and accurate mapping of interacting protein domains. This chapter describes a protocol that combines site-directed photocrosslinking to metabolic labeling of proteins and lipids as a method to characterize, with temporal and spatial resolution, the interactions of a secretory protein as it transverses the bacterial envelope.
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Affiliation(s)
- Raffaele Ieva
- Laboratoire de Microbiologie et de Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France.
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24
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Braselmann E, Chaney JL, Champion MM, Clark PL. DegP Chaperone Suppresses Toxic Inner Membrane Translocation Intermediates. PLoS One 2016; 11:e0162922. [PMID: 27626276 PMCID: PMC5023192 DOI: 10.1371/journal.pone.0162922] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Accepted: 08/30/2016] [Indexed: 11/18/2022] Open
Abstract
The periplasm of Gram-negative bacteria includes a variety of molecular chaperones that shepherd the folding and targeting of secreted proteins. A central player of this quality control network is DegP, a protease also suggested to have a chaperone function. We serendipitously discovered that production of the Bordetella pertussis autotransporter virulence protein pertactin is lethal in Escherichia coli ΔdegP strains. We investigated specific contributions of DegP to secretion of pertactin as a model system to test the functions of DegP in vivo. The DegP chaperone activity was sufficient to restore growth during pertactin production. This chaperone dependency could be relieved by changing the pertactin signal sequence: an E. coli signal sequence leading to co-translational inner membrane (IM) translocation was sufficient to suppress lethality in the absence of DegP, whereas an E. coli post-translational signal sequence was sufficient to recapitulate the lethal phenotype. These results identify a novel connection between the DegP chaperone and the mechanism used to translocate a protein across the IM. Lethality coincided with loss of periplasmic proteins, soluble σE, and proteins regulated by this essential stress response. These results suggest post-translational IM translocation can lead to the formation of toxic periplasmic folding intermediates, which DegP can suppress.
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Affiliation(s)
- Esther Braselmann
- Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, Indiana, United States of America
- * E-mail:
| | - Julie L. Chaney
- Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Matthew M. Champion
- Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Patricia L. Clark
- Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, Indiana, United States of America
- Department of Chemical & Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana, United States of America
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25
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Kuo KHM, Khan S, Rand ML, Mian HS, Brnjac E, Sandercock LE, Akula I, Julien JP, Pai EF, Chesney AE. EspP, an Extracellular Serine Protease from Enterohemorrhagic E. coli, Reduces Coagulation Factor Activities, Reduces Clot Strength, and Promotes Clot Lysis. PLoS One 2016; 11:e0149830. [PMID: 26934472 PMCID: PMC4775034 DOI: 10.1371/journal.pone.0149830] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Accepted: 02/07/2016] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND EspP (E. coli secreted serine protease, large plasmid encoded) is an extracellular serine protease produced by enterohemorrhagic E. coli (EHEC) O157:H7, a causative agent of diarrhea-associated Hemolytic Uremic Syndrome (D+HUS). The mechanism by which EHEC induces D+HUS has not been fully elucidated. OBJECTIVES We investigated the effects of EspP on clot formation and lysis in human blood. METHODS Human whole blood and plasma were incubated with EspP(WT )at various concentrations and sampled at various time points. Thrombin time (TT), prothrombin time (PT), and activated partial thromboplastin time (aPTT), coagulation factor activities, and thrombelastgraphy (TEG) were measured. RESULTS AND CONCLUSIONS Human whole blood or plasma incubated with EspP(WT) was found to have prolonged PT, aPTT, and TT. Furthermore, human whole blood or plasma incubated with EspP(WT) had reduced activities of coagulation factors V, VII, VIII, and XII, as well as prothrombin. EspP did not alter the activities of coagulation factors IX, X, or XI. When analyzed by whole blood TEG, EspP decreased the maximum amplitude of the clot, and increased the clot lysis. Our results indicate that EspP alters hemostasis in vitro by decreasing the activities of coagulation factors V, VII, VIII, and XII, and of prothrombin, by reducing the clot strength and accelerating fibrinolysis, and provide further evidence of a functional role for this protease in the virulence of EHEC and the development of D+HUS.
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Affiliation(s)
- Kevin H. M. Kuo
- Division of Medical Oncology and Hematology, University Health Network, Toronto, ON, Canada
- * E-mail:
| | - Shekeb Khan
- Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
- Campbell Family Cancer Research Institute, Ontario Cancer Institute, University Health Network, Toronto, ON, Canada
| | - Margaret L. Rand
- Division of Hematology, Hospital for Sick Children, Toronto, ON, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Hira S. Mian
- Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Elena Brnjac
- Department of Clinical Pathology, Sunnybrook Health Sciences Centre, Toronto, ON, Canada
| | - Linda E. Sandercock
- Campbell Family Cancer Research Institute, Ontario Cancer Institute, University Health Network, Toronto, ON, Canada
| | - Indira Akula
- Program in Molecular Structure and Function, The Hospital for Sick Children Research Institute, Toronto, ON, Canada
| | - Jean-Philippe Julien
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
- Program in Molecular Structure and Function, The Hospital for Sick Children Research Institute, Toronto, ON, Canada
- Department of Immunology, University of Toronto, Toronto, ON, Canada
| | - Emil F. Pai
- Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
- Campbell Family Cancer Research Institute, Ontario Cancer Institute, University Health Network, Toronto, ON, Canada
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Alden E. Chesney
- Department of Clinical Pathology, Sunnybrook Health Sciences Centre, Toronto, ON, Canada
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26
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Berry IJ, Steele JR, Padula MP, Djordjevic SP. The application of terminomics for the identification of protein start sites and proteoforms in bacteria. Proteomics 2015; 16:257-72. [DOI: 10.1002/pmic.201500319] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Revised: 09/21/2015] [Accepted: 09/30/2015] [Indexed: 01/11/2023]
Affiliation(s)
- Iain J. Berry
- The ithree Institute; University of Technology Sydney; Broadway NSW Australia
- Proteomics Core Facility; University of Technology Sydney; Broadway NSW Australia
| | - Joel R. Steele
- Proteomics Core Facility; University of Technology Sydney; Broadway NSW Australia
| | - Matthew P. Padula
- The ithree Institute; University of Technology Sydney; Broadway NSW Australia
- Proteomics Core Facility; University of Technology Sydney; Broadway NSW Australia
| | - Steven P. Djordjevic
- The ithree Institute; University of Technology Sydney; Broadway NSW Australia
- Proteomics Core Facility; University of Technology Sydney; Broadway NSW Australia
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27
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Vasilevsky S, Stojanov M, Greub G, Baud D. Chlamydial polymorphic membrane proteins: regulation, function and potential vaccine candidates. Virulence 2015; 7:11-22. [PMID: 26580416 DOI: 10.1080/21505594.2015.1111509] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Pmps (Polymorphic Membrane Proteins) are a group of membrane bound surface exposed chlamydial proteins that have been characterized as autotransporter adhesins and are important in the initial phase of chlamydial infection. These proteins all contain conserved GGA (I, L, V) and FxxN tetrapeptide motifs in the N-terminal portion of each protein. All chlamydial species express Pmps. Even in the chlamydia-related bacteria Waddlia chondrophila, a Pmp-like adhesin has been identified, demonstrating the importance of Pmps in Chlamydiales biology. Chlamydial species vary in the number of pmp genes and their differentially regulated expression during the infectious cycle or in response to stress. Studies have also demonstrated that Pmps are able to induce innate immune functional responses in infected cells, including production of IL-8, IL-6 and MCP-1, by activating the transcription factor NF-κB. Human serum studies have indicated that although anti-Pmp specific antibodies are produced in response to a chlamydial infection, the response is variable depending on the Pmp protein. In C. trachomatis, PmpB, PmpC, PmpD and PmpI were the proteins eliciting the strongest immune response among adolescents with and without pelvic inflammatory disease (PID). In contrast, PmpA and PmpE elicited the weakest antibody response. Interestingly, there seems to be a gender bias for Pmp recognition with a stronger anti-Pmp reactivity in male patients. Furthermore, anti-PmpA antibodies might contribute to adverse pregnancy outcomes, at least among women with PID. In vitro studies indicated that dendritic cells infected with C. muridarum were able to present PmpG and PmpF on their MHC class II receptors and T cells were able to recognize the MHC class-II bound peptides. In addition, vaccination with PmpEFGH and Major Outer Membrane Protein (MOMP) significantly protected mice against a genital tract C. muridarum infection, suggesting that Pmps may be an important component of a multi-subunit chlamydial vaccine. Thus, Pmps might be important not only for the pathogenesis of chlamydial infection, but also as potential candidate vaccine proteins.
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Affiliation(s)
- Sam Vasilevsky
- a Materno-fetal and Obstetrics Research Unit ; Department of Obstetrics and Gynecology; Maternity; University Hospital ; Lausanne , Switzerland
| | - Milos Stojanov
- a Materno-fetal and Obstetrics Research Unit ; Department of Obstetrics and Gynecology; Maternity; University Hospital ; Lausanne , Switzerland
| | - Gilbert Greub
- b Center for Research on Intracellular Bacteria; Institute of Microbiology; Faculty of Biology and Medicine; University of Lausanne and University Hospital ; Lausanne , Switzerland
| | - David Baud
- a Materno-fetal and Obstetrics Research Unit ; Department of Obstetrics and Gynecology; Maternity; University Hospital ; Lausanne , Switzerland
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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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Sun F, Pang X, Xie T, Zhai Y, Wang G, Sun F. BrkAutoDisplay: functional display of multiple exogenous proteins on the surface of Escherichia coli by using BrkA autotransporter. Microb Cell Fact 2015; 14:129. [PMID: 26337099 PMCID: PMC4558763 DOI: 10.1186/s12934-015-0316-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 08/10/2015] [Indexed: 01/08/2023] Open
Abstract
Background Bacterial surface display technique enables the exogenous proteins or polypeptides displayed on the bacterial surface, while maintaining their relatively independent spatial structures and biological activities. The technique makes recombinant bacteria possess the expectant functions, subsequently, directly used for many applications. Many proteins could be used to achieve bacterial surface display, among them, autotransporter, a member of the type V secretion system of gram-negative bacteria, has been extensively studied because of its modular structure and apparent simplicity. However, autotransporter has not been widely used at present due to lack of a convenient genetic vector system. With our recently characterized autotransporter BrkA (Bordetella serum-resistance killing protein A) from Bordetella pertussis, we are aiming to develop a new autotransporter-based surface display system for potential wide application. Results Here, we construct a bacterial surface display system named as BrkAutoDisplay, based on the structure of autotransporter BrkA. BrkAutoDisplay is a convenient system to host exogenous genes. In our test, this system is good to efficiently display various proteins on the outer membrane surface of Escherichia coli, including green fluorescent protein (GFP), various enzymes and single chain antibody. Moreover, the displayed GFP possesses green fluorescence, the enzymes CotA, EstPc and PalA exhibit catalytic activity 0.12, 6.88 and 0.32 mU (per 5.2 × 108 living bacteria cells) respectively, and the single chain antibody fragment (scFv) can bind with its antigen strongly. Finally, we showed that C41(DE3) is a good strain of E. coli for the successful functionality of BrkAutoDisplay. Conclusions We designed a new bacterial display system called as BrkAutoDisplay and displayed various exogenous proteins on E. coli surface. Our results indicate that BrkAutoDisplay system is worthy of further study for industrial applications.
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Affiliation(s)
- Fang Sun
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing, 100101, China. .,University of the Chinese Academy of Sciences, Beijing, 100049, China.
| | - Xiaoyun Pang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing, 100101, China.
| | - Tian Xie
- Key Laboratory of Environmental and Applied Microbiology, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China. .,University of the Chinese Academy of Sciences, Beijing, 100049, China.
| | - Yujia Zhai
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing, 100101, China.
| | - Ganggang Wang
- Key Laboratory of Environmental and Applied Microbiology, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China.
| | - Fei Sun
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing, 100101, China.
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30
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Qin W, Wang L, Lei L. New findings on the function and potential applications of the trimeric autotransporter adhesin. Antonie van Leeuwenhoek 2015; 108:1-14. [PMID: 26014492 DOI: 10.1007/s10482-015-0477-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2015] [Accepted: 05/08/2015] [Indexed: 11/27/2022]
Abstract
Trimeric autotransporter adhesins (TAAs) are located on the surface of many pathogenic Gram-negative bacteria. TAAs belong to the autotransporter protein family and consist of three identical monomers. These obligate homotrimeric proteins are secreted through the bacterial type Vc secretion system and share a common molecular organization that each monomer consists of a N-terminal "passenger" domain and a C-terminal translocation domain. TAAs are important virulence factors that are involved in bacterial life cycle and participate in mediating infection, invasion, dissemination and evasion of host immune responses. TAAs have also proved to be useful for many applications, such as vaccines and disease biomarkers. We here mainly focused on new findings on bio-function and application of TAAs in addition to their common structure and secretion mechanisms.
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Affiliation(s)
- Wanhai Qin
- College of Veterinary Medicine, Jilin University, Xi'an Road 5333, Changchun, China,
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31
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Bernstein HD. Looks can be deceiving: recent insights into the mechanism of protein secretion by the autotransporter pathway. Mol Microbiol 2015; 97:205-15. [PMID: 25881492 DOI: 10.1111/mmi.13031] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/15/2015] [Indexed: 12/14/2022]
Abstract
Autotransporters are a large superfamily of cell surface proteins produced by Gram-negative bacteria that consist of an N-terminal extracellular domain ('passenger domain') and a C-terminal β-barrel domain that resides in the outer membrane (OM). Although it was originally proposed that the passenger domain is translocated across the OM through a channel formed exclusively by the covalently linked β-barrel domain, this idea has been strongly challenged by a variety of observations. Recent experimental results have suggested a new model in which both the translocation of the passenger domain and the membrane integration of the β-barrel domain are facilitated by the Bam complex, a highly conserved heteroligomer that plays a general role in OM protein assembly. Other factors, including periplasmic chaperones and inner membrane proteins, have also recently been implicated in the biogenesis of at least some members of the autotransporter superfamily. New results have raised intriguing questions about the energetics of the secretion reaction and the relationship between the assembly of autotransporters and the assembly of other classes of OM proteins. Concomitantly, new mechanistic and structural insights have expanded the utility of the autotransporter pathway for the surface display of heterologous peptides and proteins of interest.
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Affiliation(s)
- Harris D Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA
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32
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Drobnak I, Braselmann E, Clark PL. Multiple driving forces required for efficient secretion of autotransporter virulence proteins. J Biol Chem 2015; 290:10104-16. [PMID: 25670852 DOI: 10.1074/jbc.m114.629170] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2014] [Indexed: 01/14/2023] Open
Abstract
Autotransporter (AT) proteins are a broad class of virulence proteins from Gram-negative bacterial pathogens that require their own C-terminal transmembrane domain to translocate their N-terminal passenger across the bacterial outer membrane (OM). But given the unavailability of ATP or a proton gradient across the OM, it is unknown what energy source(s) drives this process. Here we used a combination of computational and experimental approaches to quantitatively compare proposed AT OM translocation mechanisms. We show directly for the first time that when translocation was blocked an AT passenger remained unfolded in the periplasm. We demonstrate that AT secretion is a kinetically controlled, non-equilibrium process coupled to folding of the passenger and propose a model connecting passenger conformation to secretion kinetics. These results reconcile seemingly contradictory reports regarding the importance of passenger folding as a driving force for OM translocation but also reveal that another energy source is required to initiate translocation.
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Affiliation(s)
- Igor Drobnak
- From the Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556
| | - Esther Braselmann
- From the Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556
| | - Patricia L Clark
- From the Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556
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33
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Roman-Hernandez G, Bernstein HD. An In Vitro Assay for Outer Membrane Protein Assembly by the BAM Complex. Methods Mol Biol 2015; 1329:203-13. [PMID: 26427687 DOI: 10.1007/978-1-4939-2871-2_16] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
To elucidate the mechanism of a biochemical process it is often essential to reconstitute the reaction in vitro using the minimal set of factors required to drive the reaction to completion. Here, we describe a method to reconstitute the folding and membrane integration of bacterial outer membrane (OM) proteins that have a characteristic β-barrel structure. In this method the BAM complex, a heteroligomer that catalyzes the membrane integration of β-barrel proteins, is first purified and inserted into small lipid vesicles. Denatured OM proteins are then assembled and integrated into the vesicles in the presence of a molecular chaperone called SurA.
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Affiliation(s)
- Giselle Roman-Hernandez
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Harris D Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA.
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34
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Gillespie JJ, Kaur SJ, Rahman MS, Rennoll-Bankert K, Sears KT, Beier-Sexton M, Azad AF. Secretome of obligate intracellular Rickettsia. FEMS Microbiol Rev 2014; 39:47-80. [PMID: 25168200 DOI: 10.1111/1574-6976.12084] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The genus Rickettsia (Alphaproteobacteria, Rickettsiales, Rickettsiaceae) is comprised of obligate intracellular parasites, with virulent species of interest both as causes of emerging infectious diseases and for their potential deployment as bioterrorism agents. Currently, there are no effective commercially available vaccines, with treatment limited primarily to tetracycline antibiotics, although others (e.g. josamycin, ciprofloxacin, chloramphenicol, and azithromycin) are also effective. Much of the recent research geared toward understanding mechanisms underlying rickettsial pathogenicity has centered on characterization of secreted proteins that directly engage eukaryotic cells. Herein, we review all aspects of the Rickettsia secretome, including six secretion systems, 19 characterized secretory proteins, and potential moonlighting proteins identified on surfaces of multiple Rickettsia species. Employing bioinformatics and phylogenomics, we present novel structural and functional insight on each secretion system. Unexpectedly, our investigation revealed that the majority of characterized secretory proteins have not been assigned to their cognate secretion pathways. Furthermore, for most secretion pathways, the requisite signal sequences mediating translocation are poorly understood. As a blueprint for all known routes of protein translocation into host cells, this resource will assist research aimed at uniting characterized secreted proteins with their apposite secretion pathways. Furthermore, our work will help in the identification of novel secreted proteins involved in rickettsial 'life on the inside'.
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Affiliation(s)
- Joseph J Gillespie
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Simran J Kaur
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - M Sayeedur Rahman
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Kristen Rennoll-Bankert
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Khandra T Sears
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Magda Beier-Sexton
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Abdu F Azad
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD, USA
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35
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Jong WSP, Daleke-Schermerhorn MH, Vikström D, Ten Hagen-Jongman CM, de Punder K, van der Wel NN, van de Sandt CE, Rimmelzwaan GF, Follmann F, Agger EM, Andersen P, de Gier JW, Luirink J. An autotransporter display platform for the development of multivalent recombinant bacterial vector vaccines. Microb Cell Fact 2014; 13:162. [PMID: 25421093 PMCID: PMC4252983 DOI: 10.1186/s12934-014-0162-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 11/02/2014] [Indexed: 01/02/2023] Open
Abstract
Background The Autotransporter pathway, ubiquitous in Gram-negative bacteria, allows the efficient secretion of large passenger proteins via a relatively simple mechanism. Capitalizing on its crystal structure, we have engineered the Escherichia coli autotransporter Hemoglobin protease (Hbp) into a versatile platform for secretion and surface display of multiple heterologous proteins in one carrier molecule. Results As proof-of-concept, we demonstrate efficient secretion and high-density display of the sizeable Mycobacterium tuberculosis antigens ESAT6, Ag85B and Rv2660c in E. coli simultaneously. Furthermore, we show stable multivalent display of these antigens in an attenuated Salmonella Typhimurium strain upon chromosomal integration. To emphasize the versatility of the Hbp platform, we also demonstrate efficient expression of multiple sizeable antigenic fragments from Chlamydia trachomatis and the influenza A virus at the Salmonella cell surface. Conclusions The successful efficient cell surface display of multiple antigens from various pathogenic organisms highlights the potential of Hbp as a universal platform for the development of multivalent recombinant bacterial vector vaccines. Electronic supplementary material The online version of this article (doi:10.1186/s12934-014-0162-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Wouter S P Jong
- Department of Molecular Cell Biology, Section Molecular Microbiology, Faculty of Earth and Life Sciences, VU University, De Boelelaan 1085, 1081, HV, Amsterdam, The Netherlands. .,Abera Bioscience AB, SE-111 45, Stockholm, Sweden.
| | - Maria H Daleke-Schermerhorn
- Department of Molecular Cell Biology, Section Molecular Microbiology, Faculty of Earth and Life Sciences, VU University, De Boelelaan 1085, 1081, HV, Amsterdam, The Netherlands. .,Abera Bioscience AB, SE-111 45, Stockholm, Sweden.
| | - David Vikström
- Xbrane Bioscience AB, SE-111 45, Stockholm, Sweden. .,Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91, Stockholm, Sweden.
| | - Corinne M Ten Hagen-Jongman
- Department of Molecular Cell Biology, Section Molecular Microbiology, Faculty of Earth and Life Sciences, VU University, De Boelelaan 1085, 1081, HV, Amsterdam, The Netherlands. .,Abera Bioscience AB, SE-111 45, Stockholm, Sweden.
| | - Karin de Punder
- The Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, 1066, CX, Amsterdam, The Netherlands. .,Present Address: Institute for Medical Psychology, Charité Universitätsmedizin, 10117, Berlin, Germany.
| | - Nicole N van der Wel
- The Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, 1066, CX, Amsterdam, The Netherlands. .,Present Address: Department of Cell Biology and Histology, Academic Medical Center, University of Amsterdam, 1105, AZ, Amsterdam, The Netherlands.
| | | | - Guus F Rimmelzwaan
- Department of Viroscience, Erasmus Medical Center, 3015, GE, Rotterdam, The Netherlands.
| | - Frank Follmann
- Department of Infectious Disease & Immunology, Statens Serum Institut, Copenhagen, Denmark.
| | - Else Marie Agger
- Department of Infectious Disease & Immunology, Statens Serum Institut, Copenhagen, Denmark.
| | - Peter Andersen
- Department of Infectious Disease & Immunology, Statens Serum Institut, Copenhagen, Denmark.
| | - Jan-Willem de Gier
- Xbrane Bioscience AB, SE-111 45, Stockholm, Sweden. .,Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91, Stockholm, Sweden.
| | - Joen Luirink
- Department of Molecular Cell Biology, Section Molecular Microbiology, Faculty of Earth and Life Sciences, VU University, De Boelelaan 1085, 1081, HV, Amsterdam, The Netherlands. .,Abera Bioscience AB, SE-111 45, Stockholm, Sweden.
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36
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Drobnak I, Braselmann E, Chaney JL, Leyton DL, Bernstein HD, Lithgow T, Luirink J, Nataro JP, Clark PL. Of linkers and autochaperones: an unambiguous nomenclature to identify common and uncommon themes for autotransporter secretion. Mol Microbiol 2014; 95:1-16. [PMID: 25345653 DOI: 10.1111/mmi.12838] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/21/2014] [Indexed: 01/02/2023]
Abstract
Autotransporter (AT) proteins provide a diverse array of important virulence functions to Gram-negative bacterial pathogens, and have also been adapted for protein surface display applications. The 'autotransporter' moniker refers to early models that depicted these proteins facilitating their own translocation across the bacterial outer membrane. Although translocation is less autonomous than originally proposed, AT protein segments upstream of the C-terminal transmembrane β-barrel have nevertheless consistently been found to contribute to efficient translocation and/or folding of the N-terminal virulence region (the 'passenger'). However, defining the precise secretion functions of these AT regions has been complicated by the use of multiple overlapping and ambiguous terms to define AT sequence, structural, and functional features, including 'autochaperone', 'linker' and 'junction'. Moreover, the precise definitions and boundaries of these features vary among ATs and even among research groups, leading to an overall murky picture of the contributions of specific features to translocation. Here we propose a unified, unambiguous nomenclature for AT structural, functional and conserved sequence features, based on explicit criteria. Applied to 16 well-studied AT proteins, this nomenclature reveals new commonalities for translocation but also highlights that the autochaperone function is less closely associated with a conserved sequence element than previously believed.
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Affiliation(s)
- Igor Drobnak
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
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37
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Haemophilus influenzae surface fibril (Hsf) is a unique twisted hairpin-like trimeric autotransporter. Int J Med Microbiol 2014; 305:27-37. [PMID: 25465160 DOI: 10.1016/j.ijmm.2014.10.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Revised: 10/08/2014] [Accepted: 10/18/2014] [Indexed: 11/21/2022] Open
Abstract
The Haemophilus surface fibril (Hsf) is an extraordinary large (2413 amino acids) trimeric autotransporter, present in all encapsulated Haemophilus influenzae. It contributes to virulence by directly functioning as an adhesin. Furthermore, Hsf recruits the host factor vitronectin thereby inhibiting the host innate immune response resulting in enhanced survival in serum. Here we observed by electron microscopy that Hsf appears as an 100 nm long fibril at the bacterial surface albeit the length is approximately 200 nm according to a bioinformatics based model. To unveil this discrepancy, we denaturated Hsf at the surface of Hib by using guanidine hydrochloride (GuHCl). Partial denaturation induced in the presence of GuHCl unfolded the Hsf molecules, and resulted in an increased length of fibres in comparison to the native trimeric form. Importantly, our findings were also verified by E. coli expressing Hsf at its surface. In addition, a set of Hsf-specific peptide antibodies also indicated that the N-terminal of Hsf is located near the C-terminal at the base of the fibril. Taken together, our results demonstrated that Hsf is not a straight molecule but is folded and doubled over. This is the first report that provides the unique structural features of the trimeric autotransporter Hsf.
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38
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Roman-Hernandez G, Peterson JH, Bernstein HD. Reconstitution of bacterial autotransporter assembly using purified components. eLife 2014; 3:e04234. [PMID: 25182416 PMCID: PMC4174580 DOI: 10.7554/elife.04234] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2014] [Accepted: 09/01/2014] [Indexed: 12/22/2022] Open
Abstract
Autotransporters are a superfamily of bacterial virulence factors consisting of an N-terminal extracellular (‘passenger’) domain and a C-terminal β barrel (‘β’) domain that resides in the outer membrane (OM). The mechanism by which the passenger domain is secreted is poorly understood. Here we show that a conserved OM protein insertase (the Bam complex) and a molecular chaperone (SurA) are both necessary and sufficient to promote the complete assembly of the Escherichia coli O157:H7 autotransporter EspP in vitro. Our results indicate that the membrane integration of the β domain is the rate-limiting step in autotransporter assembly and that passenger domain translocation does not require the input of external energy. Furthermore, experiments using nanodiscs strongly suggest that autotransporter assembly is catalyzed by a single copy of the Bam complex. Finally, we describe a method to purify a highly active form of the Bam complex that should facilitate the elucidation of its function. DOI:http://dx.doi.org/10.7554/eLife.04234.001 Disease-causing bacteria release molecules called virulence factors to help them infect their host. These virulence factors need to pass through the membrane that surrounds the cell. Indeed, some bacteria, such as Escherichia coli, have two membranes, so some virulence factors need to pass through an extra membrane. One group of virulence factors found in E. coli are called autotransporters. These proteins have two sections: the passenger domain, which is the main part of the virulence factor, and the β domain, which anchors the autotransporter in the outer membrane. Once the passenger domain is outside the cell, the link to the β domain can be broken to release the virulence factor. However, we do not know how the passenger domain passes through the outer membrane. By studying an E. coli autotransporter called EspP, Roman-Hernandez et al. have now identified the other proteins that are required for the β domain to insert into an artificial membrane, and allow the passenger domain to pass through the membrane. These other proteins are a group of proteins called the Bam complex and a chaperone protein called SurA. The experiments also show that an external source of energy is not needed to drive this process, and they suggest that the passenger domain moves through a hole in the outer membrane formed by the β domain and/or the Bam complex. Roman-Hernandez et al. also developed a new way to purify the Bam complex that should help all researchers working on this set of proteins. DOI:http://dx.doi.org/10.7554/eLife.04234.002
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Affiliation(s)
- Giselle Roman-Hernandez
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, United States
| | - Janine H Peterson
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, United States
| | - Harris D Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, United States
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van Ulsen P, Rahman SU, Jong WS, Daleke-Schermerhorn MH, Luirink J. Type V secretion: From biogenesis to biotechnology. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1592-611. [DOI: 10.1016/j.bbamcr.2013.11.006] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 11/01/2013] [Accepted: 11/13/2013] [Indexed: 12/13/2022]
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Decoration of outer membrane vesicles with multiple antigens by using an autotransporter approach. Appl Environ Microbiol 2014; 80:5854-65. [PMID: 25038093 DOI: 10.1128/aem.01941-14] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Outer membrane vesicles (OMVs) are spherical nanoparticles that naturally shed from Gram-negative bacteria. They are rich in immunostimulatory proteins and lipopolysaccharide but do not replicate, which increases their safety profile and renders them attractive vaccine vectors. By packaging foreign polypeptides in OMVs, specific immune responses can be raised toward heterologous antigens in the context of an intrinsic adjuvant. Antigens exposed at the vesicle surface have been suggested to elicit protection superior to that from antigens concealed inside OMVs, but hitherto robust methods for targeting heterologous proteins to the OMV surface have been lacking. We have exploited our previously developed hemoglobin protease (Hbp) autotransporter platform for display of heterologous polypeptides at the OMV surface. One, two, or three of the Mycobacterium tuberculosis antigens ESAT6, Ag85B, and Rv2660c were targeted to the surface of Escherichia coli OMVs upon fusion to Hbp. Furthermore, a hypervesiculating ΔtolR ΔtolA derivative of attenuated Salmonella enterica serovar Typhimurium SL3261 was generated, enabling efficient release and purification of OMVs decorated with multiple heterologous antigens, exemplified by the M. tuberculosis antigens and epitopes from Chlamydia trachomatis major outer membrane protein (MOMP). Also, we showed that delivery of Salmonella OMVs displaying Ag85B to antigen-presenting cells in vitro results in processing and presentation of an epitope that is functionally recognized by Ag85B-specific T cell hybridomas. In conclusion, the Hbp platform mediates efficient display of (multiple) heterologous antigens, individually or combined within one molecule, at the surface of OMVs. Detection of antigen-specific immune responses upon vesicle-mediated delivery demonstrated the potential of our system for vaccine development.
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A mortise-tenon joint in the transmembrane domain modulates autotransporter assembly into bacterial outer membranes. Nat Commun 2014; 5:4239. [PMID: 24967730 DOI: 10.1038/ncomms5239] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 05/28/2014] [Indexed: 11/08/2022] Open
Abstract
Bacterial autotransporters comprise a 12-stranded membrane-embedded β-barrel domain, which must be folded in a process that entraps segments of an N-terminal passenger domain. This first stage of autotransporter folding determines whether subsequent translocation can deliver the N-terminal domain to its functional form on the bacterial cell surface. Here, paired glycine-aromatic 'mortise and tenon' motifs are shown to join neighbouring β-strands in the C-terminal barrel domain, and mutations within these motifs slow the rate and extent of passenger domain translocation to the surface of bacterial cells. In line with this, biophysical studies of the autotransporter Pet show that the conserved residues significantly quicken completion of the folding reaction and promote stability of the autotransporter barrel domain. Comparative genomics demonstrate conservation of glycine-aromatic residue pairings through evolution as a previously unrecognized feature of all autotransporter proteins.
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42
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Beck CM, Diner EJ, Kim JJ, Low DA, Hayes CS. The F pilus mediates a novel pathway of CDI toxin import. Mol Microbiol 2014; 93:276-90. [PMID: 24889811 DOI: 10.1111/mmi.12658] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/27/2014] [Indexed: 11/29/2022]
Abstract
Contact-dependent growth inhibition (CDI) is a widespread form of inter-bacterial competition that requires direct cell-to-cell contact. CDI(+) inhibitor cells express CdiA effector proteins on their surface. CdiA binds to specific receptors on susceptible target bacteria and delivers a toxin derived from its C-terminal region (CdiA-CT). Here, we show that purified CdiA-CT(536) toxin from uropathogenic Escherichia coli 536 translocates into bacteria, thereby by-passing the requirement for cell-to-cell contact during toxin delivery. Genetic analyses demonstrate that the N-terminal domain of CdiA-CT(536) is necessary and sufficient for toxin import. The CdiA receptor plays no role in this import pathway; nor do the Tol and Ton systems, which are exploited to internalize colicin toxins. Instead, CdiA-CT(536) import requires conjugative F pili. We provide evidence that the N-terminal domain of CdiA-CT(536) interacts with F pilin, and that pilus retraction is critical for toxin import. This pathway is reminiscent of the strategy used by small RNA leviviruses to infect F(+) cells. We propose that CdiA-CT(536) mimics the pilin-binding maturation proteins of leviviruses, allowing the toxin to bind F pili and become internalized during pilus retraction.
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Affiliation(s)
- Christina M Beck
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, 93106-9625, USA
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43
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Kang'ethe W, Bernstein HD. Stepwise folding of an autotransporter passenger domain is not essential for its secretion. J Biol Chem 2013; 288:35028-38. [PMID: 24165126 DOI: 10.1074/jbc.m113.515635] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Autotransporters are a superfamily of virulence proteins produced by Gram-negative bacteria. They consist of an N-terminal β-helical domain ("passenger domain") that is secreted into the extracellular space and a C-terminal β-barrel domain ("β-domain") that anchors the protein to the outer membrane. Because the periplasm lacks ATP, vectorial folding of the passenger domain in a C-to-N-terminal direction has been proposed to drive the secretion reaction. Consistent with this hypothesis, mutations that disrupt the folding of the C terminus of the passenger domain of the Escherichia coli O157:H7 autotransporter EspP have been shown to cause strong secretion defects. Here, we show that point mutations introduced at specific locations near the middle or N terminus of the EspP β-helix that perturb folding also impair secretion, but to a lesser degree. Surprisingly, we found that even multiple mutations that potentially abolish the stability of several consecutive rungs of the β-helix only moderately reduce secretion efficiency. Although these results provide evidence that the free energy derived from passenger domain folding contributes to secretion efficiency, they also suggest that a significant fraction of the energy required for secretion is derived from another source.
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Affiliation(s)
- Wanyoike Kang'ethe
- From the Genetics and Biochemistry Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892
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44
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Charge-dependent secretion of an intrinsically disordered protein via the autotransporter pathway. Proc Natl Acad Sci U S A 2013; 110:E4246-55. [PMID: 24145447 DOI: 10.1073/pnas.1310345110] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Autotransporters are a large class of virulence proteins produced by Gram-negative bacteria. They contain an N-terminal extracellular ("passenger") domain that folds into a β-helical structure and a C-terminal β-barrel ("β") domain that anchors the protein to the outer membrane. Because the periplasm lacks ATP, the source of energy that drives passenger domain secretion is unknown. The prevailing model postulates that vectorial folding of the β-helix in the extracellular space facilitates unidirectional secretion of the passenger domain. In this study we used a chimeric protein composed of the 675-residue receptor-binding domain (RD) of the Bordetella pertussis adenylate cyclase toxin CyaA fused to the C terminus of the Escherichia coli O157:H7 autotransporter EspP to test this hypothesis. The RD is a highly acidic, repetitive polypeptide that is intrinsically disordered in the absence of calcium. Surprisingly, we found that the RD moiety was efficiently secreted when it remained in an unfolded conformation. Furthermore, we found that neutralizing or reversing the charge of acidic amino acid clusters stalled translocation in the vicinity of the altered residues. These results challenge the vectorial folding model and, together with the finding that naturally occurring passenger domains are predominantly acidic, provide evidence that a net negative charge plays a significant role in driving the translocation reaction.
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45
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Besingi RN, Chaney JL, Clark PL. An alternative outer membrane secretion mechanism for an autotransporter protein lacking a C-terminal stable core. Mol Microbiol 2013; 90:1028-45. [PMID: 24118465 DOI: 10.1111/mmi.12414] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/24/2013] [Indexed: 01/24/2023]
Abstract
Autotransporter (AT) proteins are a broad class of virulence factors from Gram-negative pathogens. AT outer membrane (OM) secretion appears simple in many regards, yet the mechanism that enables transport of the central AT 'passenger' across the OM remains unclear. OM secretion efficiency for two AT passengers is enhanced by approximately 20 kDa stable core at the C-terminus of the passenger, but studies on a broader range of AT proteins are needed in order to determine whether a stability difference between the passenger N- and C-terminus represents a truly common mechanistic feature. Yersinia pestis YapV is homologous to Shigella flexneri IcsA, and like IcsA, YapV recruits mammalian neural Wiskott-Aldrich syndrome protein (N-WASP). In vitro, the purified YapV passenger is functional and rich in β-sheet structure, but lacks a approximately 20 kDa C-terminal stable core. However, the N-terminal 49 residues of the YapV passenger globally destabilize the entire YapV passenger, enhancing its OM secretion efficiency. These results indicate that the contributions of AT passenger sequences to OM secretion efficiency extend beyond a C-terminal stable core, and highlight a role of the passenger N-terminus in reducing passenger stability in order to facilitate OM secretion of some AT proteins.
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Affiliation(s)
- Richard N Besingi
- Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
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46
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Ruiz-Perez F, Nataro JP. Bacterial serine proteases secreted by the autotransporter pathway: classification, specificity, and role in virulence. Cell Mol Life Sci 2013; 71:745-70. [PMID: 23689588 DOI: 10.1007/s00018-013-1355-8] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 04/25/2013] [Accepted: 04/29/2013] [Indexed: 01/07/2023]
Abstract
Serine proteases exist in eukaryotic and prokaryotic organisms and have emerged during evolution as the most abundant and functionally diverse group. In Gram-negative bacteria, there is a growing family of high molecular weight serine proteases secreted to the external milieu by a fascinating and widely employed bacterial secretion mechanism, known as the autotransporter pathway. They were initially found in Neisseria, Shigella, and pathogenic Escherichia coli, but have now also been identified in Citrobacter rodentium, Salmonella, and Edwardsiella species. Here, we focus on proteins belonging to the serine protease autotransporter of Enterobacteriaceae (SPATEs) family. Recent findings regarding the predilection of serine proteases to host intracellular or extracellular protein-substrates involved in numerous biological functions, such as those implicated in cytoskeleton stability, autophagy or innate and adaptive immunity, have helped provide a better understanding of SPATEs' contributions in pathogenesis. Here, we discuss their classification, substrate specificity, and potential roles in pathogenesis.
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Affiliation(s)
- Fernando Ruiz-Perez
- Department of Pediatrics, School of Medicine, University of Virginia, P.O.Box 800326, MR4 Room 4012C, 409 Lane Road, Charlottesville, VA, 22908, USA,
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Grijpstra J, Arenas J, Rutten L, Tommassen J. Autotransporter secretion: varying on a theme. Res Microbiol 2013; 164:562-82. [PMID: 23567321 DOI: 10.1016/j.resmic.2013.03.010] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Accepted: 02/28/2013] [Indexed: 10/27/2022]
Abstract
Autotransporters are widely distributed among Gram-negative bacteria. They can have a large variety of functions and many of them have a role in virulence. They are synthesized as large precursors with an N-terminal signal sequence that mediates transport across the inner membrane via the Sec machinery and a translocator domain that mediates the transport of the connected passenger domain across the outer membrane to the bacterial cell surface. Like integral outer membrane proteins, the translocator domain folds in a β-barrel structure and requires the Bam machinery for its insertion into the outer membrane. After transport across the outer membrane, the passenger may stay connected via the translocator domain to the bacterial cell surface or it is proteolytically released into the extracellular milieu. Based on the size of the translocator domain and its position relative to the passenger in the precursor, autotransporters are divided into four sub-categories. We review here the current knowledge of the biogenesis, structure and function of various autotransporters.
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Affiliation(s)
- Jan Grijpstra
- Section Molecular Microbiology, Department of Biology, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
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48
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Mechanistic link between β barrel assembly and the initiation of autotransporter secretion. Proc Natl Acad Sci U S A 2013; 110:E938-47. [PMID: 23431155 DOI: 10.1073/pnas.1219076110] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Autotransporters are bacterial virulence factors that contain an N-terminal extracellular ("passenger") domain and a C-terminal β barrel ("β") domain that anchors the protein to the outer membrane. The β domain is required for passenger domain secretion, but its exact role in autotransporter biogenesis is unclear. Here we describe insights into the function of the β domain that emerged from an analysis of mutations in the Escherichia coli O157:H7 autotransporter EspP. We found that the G1066A and G1081D mutations slightly distort the structure of the β domain and delay the initiation of passenger domain translocation. Site-specific photocrosslinking experiments revealed that the mutations slow the insertion of the β domain into the outer membrane, but do not delay the binding of the β domain to the factor that mediates the insertion reaction (the Bam complex). Our results demonstrate that the β domain does not simply target the passenger domain to the outer membrane, but promotes translocation when it reaches a specific stage of assembly. Furthermore, our results provide evidence that the Bam complex catalyzes the membrane integration of β barrel proteins in a multistep process that can be perturbed by minor structural defects in client proteins.
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Adaptation of low-resolution methods for the study of yeast microsomal polytopic membrane proteins: a methodological review. Biochem Soc Trans 2013; 41:35-42. [DOI: 10.1042/bst20120212] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Most integral membrane proteins of yeast with two or more membrane-spanning sequences have not yet been crystallized and for many of them the side on which the active sites or ligand-binding domains reside is unknown. Also, bioinformatic topology predictions are not yet fully reliable. However, so-called low-resolution biochemical methods can be used to locate hydrophilic loops or individual residues of polytopic membrane proteins at one or the other side of the membrane. The advantages and limitations of several such methods for topological studies with yeast ER integral membrane proteins are discussed. We also describe new tools that allow us to better control and validate results obtained with SCAM (substituted cysteine accessibility method), an approach that determines the position of individual residues with respect to the membrane plane, whereby only minimal changes in the primary sequence have to be introduced into the protein of interest.
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50
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Weiss A, Brockmeyer J. Prevalence, biogenesis, and functionality of the serine protease autotransporter EspP. Toxins (Basel) 2012; 5:25-48. [PMID: 23274272 PMCID: PMC3564066 DOI: 10.3390/toxins5010025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Revised: 12/18/2012] [Accepted: 12/21/2012] [Indexed: 11/24/2022] Open
Abstract
Enterohemorrhagic E. coli (EHEC) causes severe diseases in humans worldwide. One of its virulence factors is EspP, which belongs to the serine protease autotransporters of Enterobacteriaceae (SPATE) family. In this review we recapitulate the current data on prevalence, biogenesis, structural properties and functionality. EspP has been used to investigate mechanistic details of autotransport, and recent studies indicate that this transport mechanism is not autonomous but rather dependent on additional factors. Currently, five subtypes have been identified (EspPα-EspPε), with EspPα being associated with highly virulent EHEC serotypes and isolates from patients with severe disease. EspPα has been shown to degrade major proteins of the complement cascade, namely C3 and C5 and probably interferes with hemostasis by cleavage of coagulation factor V. Furthermore, EspPα is believed to contribute to biofilm formation perhaps by polymerization to rope-like structures. Together with the proteolytic activity, EspPα might ameliorate host colonization and interfere with host response.
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Affiliation(s)
- André Weiss
- Institute of Food Chemistry, Corrensstraße 45, Münster 48149, Germany.
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