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Liu H, Xu G, Guo B, Liu F. Old role with new feature: T2SS ATPase as a cyclic-di-GMP receptor to regulate antibiotic production. Appl Environ Microbiol 2024; 90:e0041824. [PMID: 38624198 PMCID: PMC11107153 DOI: 10.1128/aem.00418-24] [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: 03/04/2024] [Accepted: 03/26/2024] [Indexed: 04/17/2024] Open
Abstract
Cyclic di-GMP (c-di-GMP) is a crucial signaling molecule found extensively in bacteria, involved in the regulation of various physiological and biochemical processes such as biofilm formation, motility, and pathogenicity through binding to downstream receptors. However, the structural dissimilarity of c-di-GMP receptor proteins has hindered the discovery of many such proteins. In this study, we identified LspE, a homologous protein of the type II secretion system (T2SS) ATPase GspE in Lysobacter enzymogenes, as a receptor protein for c-di-GMP. We identified the more conservative c-di-GMP binding amino acid residues as K358 and T359, which differ from the previous reports, indicating that GspE proteins may represent a class of c-di-GMP receptor proteins. Additionally, we found that LspE in L. enzymogenes also possesses a novel role in regulating the production of the antifungal antibiotic HSAF. Further investigations revealed the critical involvement of both ATPase activity and c-di-GMP binding in LspE-mediated regulation of HSAF (Heat-Stable Antifungal Factor) production, with c-di-GMP binding having no impact on LspE's ATPase activity. This suggests that the control of HSAF production by LspE encompasses two distinct processes: c-di-GMP binding and the inherent ATPase activity of LspE. Overall, our study unraveled a new function for the conventional protein GspE of the T2SS as a c-di-GMP receptor protein and shed light on its role in regulating antibiotic production.IMPORTANCEThe c-di-GMP signaling pathway in bacteria is highly intricate. The identification and functional characterization of novel receptor proteins have posed a significant challenge in c-di-GMP research. The type II secretion system (T2SS) is a well-studied secretion system in bacteria. In this study, our findings revealed the ATPase GspE protein of the T2SS as a class of c-di-GMP receptor protein. Notably, we discovered its novel function in regulating the production of antifungal antibiotic HSAF in Lysobacter enzymogenes. Given that GspE may be a conserved c-di-GMP receptor protein, it is worthwhile for researchers to reevaluate its functional roles and mechanisms across diverse bacterial species.
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Affiliation(s)
- Haofei Liu
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Gaoge Xu
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base, Ministry of Science and Technology, Nanjing, China
- School of Plant Protection, Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests, Ministry of Education, Hainan University, Haikou, China
| | - Baodian Guo
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base, Ministry of Science and Technology, Nanjing, China
| | - Fengquan Liu
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base, Ministry of Science and Technology, Nanjing, China
- Department of Plant Pathology, College of Agriculture, Guizhou University, Guiyang, China
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Meng R, Xing Z, Chang JY, Yu Z, Thongchol J, Xiao W, Wang Y, Chamakura K, Zeng Z, Wang F, Young R, Zeng L, Zhang J. Structural basis of Acinetobacter type IV pili targeting by an RNA virus. Nat Commun 2024; 15:2746. [PMID: 38553443 PMCID: PMC10980823 DOI: 10.1038/s41467-024-47119-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Accepted: 03/20/2024] [Indexed: 04/02/2024] Open
Abstract
Acinetobacters pose a significant threat to human health, especially those with weakened immune systems. Type IV pili of acinetobacters play crucial roles in virulence and antibiotic resistance. Single-stranded RNA bacteriophages target the bacterial retractile pili, including type IV. Our study delves into the interaction between Acinetobacter phage AP205 and type IV pili. Using cryo-electron microscopy, we solve structures of the AP205 virion with an asymmetric dimer of maturation proteins, the native Acinetobacter type IV pili bearing a distinct post-translational pilin cleavage, and the pili-bound AP205 showing its maturation proteins adapted to pilin modifications, allowing each phage to bind to one or two pili. Leveraging these results, we develop a 20-kilodalton AP205-derived protein scaffold targeting type IV pili in situ, with potential for research and diagnostics.
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Affiliation(s)
- Ran Meng
- Center for Phage Technology, Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843, USA
- Yale University, New Haven, CT, 06520, USA
| | - Zhongliang Xing
- Center for Phage Technology, Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843, USA
| | - Jeng-Yih Chang
- Center for Phage Technology, Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843, USA
- UMass Chan Medical School, Worcester, MA, 01655, USA
| | - Zihao Yu
- Center for Phage Technology, Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843, USA
| | - Jirapat Thongchol
- Center for Phage Technology, Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843, USA
| | - Wen Xiao
- Center for Phage Technology, Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843, USA
| | - Yuhang Wang
- Center for Phage Technology, Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843, USA
| | - Karthik Chamakura
- Center for Phage Technology, Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843, USA
- Armata Pharmaceuticals, Inc., Marina del Rey, CA, 90292, USA
| | - Zhiqi Zeng
- Center for Phage Technology, Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843, USA
| | - Fengbin Wang
- Department of Biochemistry and Molecular Genetics, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Ry Young
- Center for Phage Technology, Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843, USA
| | - Lanying Zeng
- Center for Phage Technology, Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843, USA
| | - Junjie Zhang
- Center for Phage Technology, Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843, USA.
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3
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Wimmi S, Fleck M, Helbig C, Brianceau C, Langenfeld K, Szymanski WG, Angelidou G, Glatter T, Diepold A. Pilotins are mobile T3SS components involved in assembly and substrate specificity of the bacterial type III secretion system. Mol Microbiol 2024; 121:304-323. [PMID: 38178634 DOI: 10.1111/mmi.15223] [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: 05/23/2023] [Revised: 12/17/2023] [Accepted: 12/20/2023] [Indexed: 01/06/2024]
Abstract
In animal pathogens, assembly of the type III secretion system injectisome requires the presence of so-called pilotins, small lipoproteins that assist the formation of the secretin ring in the outer membrane. Using a combination of functional assays, interaction studies, proteomics, and live-cell microscopy, we determined the contribution of the pilotin to the assembly, function, and substrate selectivity of the T3SS and identified potential new downstream roles of pilotin proteins. In absence of its pilotin SctG, Yersinia enterocolitica forms few, largely polar injectisome sorting platforms and needles. Accordingly, most export apparatus subcomplexes are mobile in these strains, suggesting the absence of fully assembled injectisomes. Remarkably, while absence of the pilotin all but prevents export of early T3SS substrates, such as the needle subunits, it has little effect on secretion of late T3SS substrates, including the virulence effectors. We found that although pilotins interact with other injectisome components such as the secretin in the outer membrane, they mostly localize in transient mobile clusters in the bacterial membrane. Together, these findings provide a new view on the role of pilotins in the assembly and function of type III secretion injectisomes.
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Affiliation(s)
- Stephan Wimmi
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Moritz Fleck
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Carlos Helbig
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Corentin Brianceau
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Katja Langenfeld
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Witold G Szymanski
- Mass Spectrometry and Proteomics Facility, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Georgia Angelidou
- Mass Spectrometry and Proteomics Facility, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Timo Glatter
- Mass Spectrometry and Proteomics Facility, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Andreas Diepold
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
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4
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Wang M, Xiao Ma S, Darwin AJ. An inhibitor/anti-inhibitor system controls the activity of lytic transglycosylase MltF in Pseudomonas aeruginosa. mBio 2023; 14:e0202223. [PMID: 38047649 PMCID: PMC10746161 DOI: 10.1128/mbio.02022-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Accepted: 10/23/2023] [Indexed: 12/05/2023] Open
Abstract
IMPORTANCE A peptidoglycan cell wall is an essential component of almost all bacterial cell envelopes, which determines cell shape and prevents osmotic rupture. Antibiotics that interfere with peptidoglycan synthesis have been one of the most important treatments for bacterial infections. Peptidoglycan must also be hydrolyzed to incorporate new material for cell growth and division and to help accommodate important envelope-spanning systems. However, the enzymes that hydrolyze peptidoglycan must be carefully controlled to prevent autolysis. Exactly how this control is achieved is poorly understood in most cases but is a highly active area of current research. Identifying hydrolase control mechanisms has the potential to provide new targets for therapeutic intervention. The work here reports the important discovery of a novel inhibitor/anti-inhibitor system that controls the activity of a cell wall hydrolase in the human pathogen Pseudomonas aeruginosa, which also affects resistance to an antibiotic used in the clinic.
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Affiliation(s)
- Michelle Wang
- Department of Microbiology, New York University Grossman School of Medicine, New York, New York, USA
| | - Sheya Xiao Ma
- Department of Microbiology, New York University Grossman School of Medicine, New York, New York, USA
| | - Andrew J. Darwin
- Department of Microbiology, New York University Grossman School of Medicine, New York, New York, USA
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5
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Barbat B, Douzi B, Ball G, Tribout M, El Karkouri K, Kellenberger C, Voulhoux R. Insights into dynamics and gating properties of T2SS secretins. SCIENCE ADVANCES 2023; 9:eadg6996. [PMID: 37792935 PMCID: PMC10550240 DOI: 10.1126/sciadv.adg6996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Accepted: 09/05/2023] [Indexed: 10/06/2023]
Abstract
Secretins are outer membrane (OM) channels found in various bacterial nanomachines that secrete or assemble large extracellular structures. High-resolution 3D structures of type 2 secretion system (T2SS) secretins revealed bimodular channels with a C-module, holding a conserved central gate and an optional top gate, followed by an N-module for which multiple structural organizations have been proposed. Here, we perform a structure-driven in vivo study of the XcpD secretin, which validates one of the organizations of the N-module whose flexibility enables alternative conformations. We also show the existence of the central gate in vivo and its required flexibility, which is key for substrate passage and watertightness control. Last, functional, genomic, and phylogenetic analyses indicate that the optional top gate provides a gain of watertightness. Our data illustrate how the gating properties of T2SS secretins allow these large channels to overcome the duality between the necessity of preserving the OM impermeability while simultaneously promoting the secretion of large, folded effectors.
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Affiliation(s)
- Brice Barbat
- LCB-UMR7283, CNRS, Aix Marseille Université, IMM, Marseille, France
| | - Badreddine Douzi
- LCB-UMR7283, CNRS, Aix Marseille Université, IMM, Marseille, France
- Université de Lorraine, INRAE, DynAMic, Nancy, F-54000 France
| | - Geneviève Ball
- LCB-UMR7283, CNRS, Aix Marseille Université, IMM, Marseille, France
| | - Mathilde Tribout
- LCB-UMR7283, CNRS, Aix Marseille Université, IMM, Marseille, France
| | | | | | - Romé Voulhoux
- LCB-UMR7283, CNRS, Aix Marseille Université, IMM, Marseille, France
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6
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Wang M, Ma SX, Darwin AJ. An inhibitor/anti-inhibitor system controls the activity of lytic transglycosylase MltF in Pseudomonas aeruginosa. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.28.551027. [PMID: 37546783 PMCID: PMC10402148 DOI: 10.1101/2023.07.28.551027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
Most bacterial cell envelopes contain a cell wall layer made of peptidoglycan. The synthesis of new peptidoglycan is critical for cell growth, division and morphogenesis, and is also coordinated with peptidoglycan hydrolysis to accommodate the new material. However, the enzymes that cleave peptidoglycan must be carefully controlled to avoid autolysis. In recent years, some control mechanisms have begun to emerge, although there are many more questions than answers for how most cell wall hydrolases are regulated. Here, we report a novel cell wall hydrolase control mechanism in Pseudomonas aeruginosa , which we discovered during our characterization of a mutant sensitive to the overproduction of a secretin protein. The mutation affected an uncharacterized Sel1-like repeat protein encoded by the PA3978 locus. In addition to the secretin-sensitivity phenotype, PA3978 disruption also increased resistance to a β-lactam antibiotic used in the clinic. In vivo and in vitro analysis revealed that PA3978 binds to the catalytic domain of the lytic transglycosylase MltF and inhibits its activity. ΔPA3978 mutant phenotypes were suppressed by deleting mltF , consistent with them having been caused by elevated MltF activity. We also discovered another interaction partner of PA3978 encoded by the PA5502 locus. The phenotypes of a ΔPA5502 mutant suggested that PA5502 interferes with the inhibitory function of PA3978 towards MltF, and we confirmed that activity for PA5502 in vitro . Therefore, PA3978 and PA5502 form an inhibitor/anti-inhibitor system that controls MltF activity. We propose to name these proteins Ilt (inhibitor of lytic transglycosylase) and Lii (lytic transglycosylase inhibitor, inhibitor). IMPORTANCE A peptidoglycan cell wall is an essential component of almost all bacterial cell envelopes, which determines cell shape and prevents osmotic rupture. Antibiotics that interfere with peptidoglycan synthesis have been one of the most important treatments for bacterial infections. Peptidoglycan must also be hydrolyzed to incorporate new material for cell growth and division, and to help accommodate important envelope-spanning systems. However, the enzymes that hydrolyze peptidoglycan must be carefully controlled to prevent autolysis. Exactly how this control is achieved is poorly understood in most cases, but is a highly active area of current research. Identifying hydrolase control mechanisms has the potential to provide new targets for therapeutic intervention. The work here reports the important discovery of a novel inhibitor/anti-nhibitor system that controls the activity of a cell wall hydrolase in the human pathogen Pseudomonas aeruginosa , and which also affects resistance to an antibiotic used in the clinic.
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7
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Barbat B, Douzi B, Voulhoux R. Structural lessons on bacterial secretins. Biochimie 2023; 205:110-116. [PMID: 36096236 DOI: 10.1016/j.biochi.2022.08.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 07/26/2022] [Accepted: 08/31/2022] [Indexed: 11/30/2022]
Abstract
To exchange and communicate with their surroundings, bacteria have evolved multiple active and passive mechanisms for trans-envelope transport. Among the pore-forming complexes found in the outer membrane of Gram-negative bacteria, secretins are distinctive homo-oligomeric channels dedicated to the active translocation of voluminous structures such as folded proteins, assembled fibers, virus particles or DNA. Members of the bacterial secretin family share a common cylinder-shaped structure with a gated pore-forming part inserted in the outer membrane, and a periplasmic channel connected to the inner membrane components of the corresponding nanomachine. In this mini-review, we will present what recently determined 3D structures have told us about the mechanisms of translocation through secretins of large substrates to the bacterial surface or in the extracellular milieu.
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Affiliation(s)
- Brice Barbat
- LCB-UMR7283, CNRS, Aix Marseille Université, IMM, 13009, Marseille, France
| | | | - Romé Voulhoux
- LCB-UMR7283, CNRS, Aix Marseille Université, IMM, 13009, Marseille, France.
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8
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Bergeron JRC, Marlovits TC. Cryo-EM of the injectisome and type III secretion systems. Curr Opin Struct Biol 2022; 75:102403. [PMID: 35724552 PMCID: PMC10114087 DOI: 10.1016/j.sbi.2022.102403] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 05/04/2022] [Accepted: 05/16/2022] [Indexed: 11/25/2022]
Abstract
Double-membrane-spanning protein complexes, such as the T3SS, had long presented an intractable challenge for structural biology. As a consequence, until a few years ago, our molecular understanding of this fascinating complex was limited to composite models, consisting of structures of isolated domains, positioned within the overall complex. Most of the membrane-embedded components remained completely uncharacterized. In recent years, the emergence of cryo-electron microscopy (cryo-EM) as a method for determining protein structures to high resolution, has be transformative to our capacity to understand the architecture of this complex, and its mechanism of substrate transport. In this review, we summarize the recent structures of the various T3SS components, determined by cryo-EM, and highlight the regions of the complex that remain to be characterized. We also discuss the recent structural insights into the mechanism of effector transport through the T3SS. Finally, we highlight some of the challenges that remain to be tackled.
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Affiliation(s)
- Julien R C Bergeron
- Randall Centre for Cell and Molecular Biophysics, King's College London, London, UK.
| | - Thomas C Marlovits
- Centre for Structural Systems Biology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
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9
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Pei D, Dalbey RE. Membrane Translocation of Folded Proteins. J Biol Chem 2022; 298:102107. [PMID: 35671825 PMCID: PMC9251779 DOI: 10.1016/j.jbc.2022.102107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2022] [Revised: 05/31/2022] [Accepted: 06/01/2022] [Indexed: 12/01/2022] Open
Abstract
An ever-increasing number of proteins have been shown to translocate across various membranes of bacterial as well as eukaryotic cells in their folded states as a part of physiological and/or pathophysiological processes. Herein we provide an overview of the systems/processes that are established or likely to involve the membrane translocation of folded proteins, such as protein export by the twin-arginine translocation (TAT) system in bacteria and chloroplasts, unconventional protein secretion (UPS) and protein import into the peroxisome in eukaryotes, and the cytosolic entry of proteins (e.g., bacterial toxins) and viruses into eukaryotes. We also discuss the various mechanistic models that have previously been proposed for the membrane translocation of folded proteins including pore/channel formation, local membrane disruption, membrane thinning, and transport by membrane vesicles. Finally, we introduce a newly discovered vesicular transport mechanism, vesicle budding and collapse (VBC), and present evidence that VBC may represent a unifying mechanism that drives some (and potentially all) of folded protein translocation processes.
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Affiliation(s)
- Dehua Pei
- Department of Chemistry and Biochemistry, The Ohio State University, 484 West 12(th) Avenue, Columbus, OH 43210.
| | - Ross E Dalbey
- Department of Chemistry and Biochemistry, The Ohio State University, 484 West 12(th) Avenue, Columbus, OH 43210.
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Scaffolding Protein GspB/OutB Facilitates Assembly of the Dickeya dadantii Type 2 Secretion System by Anchoring the Outer Membrane Secretin Pore to the Inner Membrane and to the Peptidoglycan Cell Wall. mBio 2022; 13:e0025322. [PMID: 35546537 PMCID: PMC9239104 DOI: 10.1128/mbio.00253-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The phytopathogenic proteobacterium Dickeya dadantii secretes an array of plant cell wall-degrading enzymes and other virulence factors via the type 2 secretion system (T2SS). T2SSs are widespread among important plant, animal, and human bacterial pathogens. This multiprotein complex spans the double membrane cell envelope and secretes fully folded proteins through a large outer membrane pore formed by 15 subunits of the secretin GspD. Secretins are also found in the type 3 secretion system and the type 4 pili. Usually, specialized lipoproteins termed pilotins assist the targeting and assembly of secretins into the outer membrane. Here, we show that in D. dadantii, the pilotin acts in concert with the scaffolding protein GspB. Deletion of gspB profoundly impacts secretin assembly, pectinase secretion, and virulence. Structural studies reveal that GspB possesses a conserved periplasmic homology region domain that interacts directly with the N-terminal secretin domain. Site-specific photo-cross-linking unravels molecular details of the GspB-GspD complex in vivo. We show that GspB facilitates outer membrane targeting and assembly of the secretin pores and anchors them to the inner membrane while the C-terminal extension of GspB provides a scaffold for the secretin channel in the peptidoglycan cell wall. Phylogenetic analysis shows that in other bacteria, GspB homologs vary in length and domain composition and act in concert with either a cognate ATPase GspA or the pilotin GspS.
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11
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Molecular Investigation of Outer Membrane Channel Genes Among Multidrug Resistance Clinical Pseudomonas Aeruginosa Isolates. Rep Biochem Mol Biol 2022; 11:102-110. [PMID: 35765529 PMCID: PMC9208561 DOI: 10.52547/rbmb.11.1.102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Accepted: 09/19/2021] [Indexed: 01/11/2023]
Abstract
Background Multidrug resistance Pseudomonas aeruginosa (MDRPA) is most important issue in healthcare setting. It can secrete many virulence effector proteins via its secretion system type (T1SS-T6SS). They are using them as conductor for delivering the effector proteins outside to begins harmful effect on host cell increasing pathogenicity, competition against other microorganism and nutrient acquisition. Methods The study include investigation of 50 isolates of MDRPA for transport secretion system and resistance for antibiotics. Molecular diagnosis using P. aeruginosa specific primer pairs, investigation of AprF, HasF, XcpQ, HxcQ, PscC, CdrB, CupB3, and Hcp using specific primer pairs by PCR were also performed. Results The results revealed high resistance to beta lactam antibiotics (78% for ceftazidime, 78% for cefepime and 46% for piperacillin) can indicate possessing of isolates for beta lactamases and this confirmed by dropping resistance to piperacillin to 16% when combined with tazobactam. Also, the results shown the ability of MDRPA for pyocyanin biosynthesis using the system of genes. Conclusion The current study conclude that all isolates of P. aeruginosa were highly virulent due to their possessing of all transport secretion system to deliver different effector proteins with possible harmful effects of these proteins.
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Liu B, Chan H, Bauda E, Contreras-Martel C, Bellard L, Villard AM, Mas C, Neumann E, Fenel D, Favier A, Serrano M, Henriques AO, Rodrigues CDA, Morlot C. Structural insights into ring-building motif domains involved in bacterial sporulation. J Struct Biol 2021; 214:107813. [PMID: 34808342 DOI: 10.1016/j.jsb.2021.107813] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 10/29/2021] [Accepted: 11/15/2021] [Indexed: 02/06/2023]
Abstract
Components of specialized secretion systems, which span the inner and outer membranes in Gram-negative bacteria, include ring-forming proteins whose oligomerization was proposed to be promoted by domains called RBM for "Ring-Building Motifs". During spore formation in Gram-positive bacteria, a transport system called the SpoIIIA-SpoIIQ complex also assembles in the double membrane that surrounds the forespore following its endocytosis by the mother cell. The presence of RBM domains in some of the SpoIIIA proteins led to the hypothesis that they would assemble into rings connecting the two membranes and form a conduit between the mother cell and forespore. Among them, SpoIIIAG forms homo-oligomeric rings in vitro but the oligomerization of other RBM-containing SpoIIIA proteins, including SpoIIIAH, remains to be demonstrated. In this work, we identified RBM domains in the YhcN/YlaJ family of proteins that are not related to the SpoIIIA-SpoIIQ complex. We solved the crystal structure of YhcN from Bacillus subtilis, which confirmed the presence of a RBM fold, flanked by additional secondary structures. As the protein did not show any oligomerization ability in vitro, we investigated the structural determinants of ring formation in SpoIIIAG, SpoIIIAH and YhcN. We showed that in vitro, the conserved core of RBM domains alone is not sufficient for oligomerization while the β-barrel forming region in SpoIIIAG forms rings on its own. This work suggests that some RBMs might indeed participate in the assembly of homomeric rings but others might have evolved toward other functions.
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Affiliation(s)
- Bowen Liu
- Univ. Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France
| | - Helena Chan
- The ithree institute, University of Technology Sydney, 2007 Ultimo, NSW, Australia
| | - Elda Bauda
- Univ. Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France
| | | | - Laure Bellard
- Univ. Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France
| | | | - Caroline Mas
- Univ. Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France
| | | | - Daphna Fenel
- Univ. Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France
| | - Adrien Favier
- Univ. Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France
| | - Monica Serrano
- Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Adriano O Henriques
- Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, Oeiras, Portugal
| | | | - Cecile Morlot
- Univ. Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France.
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13
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Potteth US, Upadhyay T, Saini S, Saraogi I. Novel Antibacterial Targets in Protein Biogenesis Pathways. Chembiochem 2021; 23:e202100459. [PMID: 34643994 DOI: 10.1002/cbic.202100459] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 10/12/2021] [Indexed: 11/11/2022]
Abstract
Antibiotic resistance has emerged as a global threat due to the ability of bacteria to quickly evolve in response to the selection pressure induced by anti-infective drugs. Thus, there is an urgent need to develop new antibiotics against resistant bacteria. In this review, we discuss pathways involving bacterial protein biogenesis as attractive antibacterial targets since many of them are essential for bacterial survival and virulence. We discuss the structural understanding of various components associated with bacterial protein biogenesis, which in turn can be utilized for rational antibiotic design. We highlight efforts made towards developing inhibitors of these pathways with insights into future possibilities and challenges. We also briefly discuss other potential targets related to protein biogenesis.
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Affiliation(s)
- Upasana S Potteth
- Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhauri, Bhopal Bypass Road, Bhopal, 462066, Madhya Pradesh, India
| | - Tulsi Upadhyay
- Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhauri, Bhopal Bypass Road, Bhopal, 462066, Madhya Pradesh, India
| | - Snehlata Saini
- Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhauri, Bhopal Bypass Road, Bhopal, 462066, Madhya Pradesh, India
| | - Ishu Saraogi
- Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhauri, Bhopal Bypass Road, Bhopal, 462066, Madhya Pradesh, India.,Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhauri, Bhopal Bypass Road, Bhopal - 462066, Madhya Pradesh, India
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14
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Yaman D, Averhoff B. Functional dissection of structural regions of the Thermus thermophilus competence protein PilW: Implication in secretin complex stability, natural transformation and pilus functions. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183666. [PMID: 34143999 DOI: 10.1016/j.bbamem.2021.183666] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 04/29/2021] [Accepted: 06/01/2021] [Indexed: 01/13/2023]
Abstract
Uptake of DNA from the environment into the bacterial cytoplasm is mediated by a macromolecular transport machinery that is similar in structure and function to type IV pili (T4P) and, indeed, DNA translocator and T4P share common components. One is the secretin PilQ which is assembled into homopolymeric complexes forming highly dynamic outer membrane (OM) channels mediating pilus extrusion and DNA uptake. How PilQ interacts with the motor is still enigmatic. Here, we have used biochemical and genetic techniques to study the interaction of PilQ with PilW, a unique protein which is essential for natural transformation and T4P extrusion of T. thermophilus. PilQ and PilW form high molecular mass complexes in the OM of T. thermophilus. When pilW was deleted, PilQ complexes were no longer observed but only PilQ monomers, accompanied by a loss of DNA uptake as well as a loss of T4P and twitching motility. Piliation of a ΔpilT2/ΔpilW double mutant suggests that PilW is important for stable assembly of PilQ complexes. To analyze the role of different regions of PilW, partial deletions (pilW∆2-40, pilW∆50-150, pilW∆163-216 and pilW∆216-292) were generated and the effect on DNA uptake, PilQ complex formation and T4P functions such as twitching motility, biofilm formation and cell-cell interaction was studied. These studies revealed that a central disordered region in PilW is required for pilus dynamics. We propose that PilW is part of a protein network that connects the transport ATPase to drive different functions of the DNA translocator and T4P.
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Affiliation(s)
- Deniz Yaman
- Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt/Main, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
| | - Beate Averhoff
- Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt/Main, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany.
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15
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Hajra D, Nair AV, Chakravortty D. An elegant nano-injection machinery for sabotaging the host: Role of Type III secretion system in virulence of different human and animal pathogenic bacteria. Phys Life Rev 2021; 38:25-54. [PMID: 34090822 DOI: 10.1016/j.plrev.2021.05.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2021] [Accepted: 05/23/2021] [Indexed: 01/22/2023]
Abstract
Various Gram-negative bacteria possess a specialized membrane-bound protein secretion system known as the Type III secretion system (T3SS), which transports the bacterial effector proteins into the host cytosol thereby helping in bacterial pathogenesis. The T3SS has a special needle-like translocon that can sense the contact with the host cell membrane and translocate effectors. The export apparatus of T3SS recognizes these effector proteins bound to chaperones and translocates them into the host cell. Once in the host cell cytoplasm, these effector proteins result in modulation of the host system and promote bacterial localization and infection. Using molecular biology, bioinformatics, genetic techniques, electron microscopic studies, and mathematical modeling, the structure and function of the T3SS and the corresponding effector proteins in various bacteria have been studied. The strategies used by different human pathogenic bacteria to modulate the host system and thereby enhance their virulence mechanism using T3SS have also been well studied. Here we review the history, evolution, and general structure of the T3SS, highlighting the details of its comparison with the flagellar export machinery. Also, this article provides mechanistic details about the common role of T3SS in subversion and manipulation of host cellular processes. Additionally, this review describes specific T3SS apparatus and the role of their specific effectors in bacterial pathogenesis by considering several human and animal pathogenic bacteria.
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Affiliation(s)
- Dipasree Hajra
- Department of Microbiology & Cell Biology, Indian Institute of Science, India
| | - Abhilash Vijay Nair
- Department of Microbiology & Cell Biology, Indian Institute of Science, India
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16
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Hotinger JA, Pendergrass HA, May AE. Molecular Targets and Strategies for Inhibition of the Bacterial Type III Secretion System (T3SS); Inhibitors Directly Binding to T3SS Components. Biomolecules 2021; 11:biom11020316. [PMID: 33669653 PMCID: PMC7922566 DOI: 10.3390/biom11020316] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 02/16/2021] [Accepted: 02/17/2021] [Indexed: 01/01/2023] Open
Abstract
The type III secretion system (T3SS) is a virulence apparatus used by many Gram-negative pathogenic bacteria to cause infections. Pathogens utilizing a T3SS are responsible for millions of infections yearly. Since many T3SS knockout strains are incapable of causing systemic infection, the T3SS has emerged as an attractive anti-virulence target for therapeutic design. The T3SS is a multiprotein molecular syringe that enables pathogens to inject effector proteins into host cells. These effectors modify host cell mechanisms in a variety of ways beneficial to the pathogen. Due to the T3SS’s complex nature, there are numerous ways in which it can be targeted. This review will be focused on the direct targeting of components of the T3SS, including the needle, translocon, basal body, sorting platform, and effector proteins. Inhibitors will be considered a direct inhibitor if they have a binding partner that is a T3SS component, regardless of the inhibitory effect being structural or functional.
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17
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Weaver SJ, Ortega DR, Sazinsky MH, Dalia TN, Dalia AB, Jensen GJ. CryoEM structure of the type IVa pilus secretin required for natural competence in Vibrio cholerae. Nat Commun 2020; 11:5080. [PMID: 33033258 PMCID: PMC7545093 DOI: 10.1038/s41467-020-18866-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 09/15/2020] [Indexed: 02/07/2023] Open
Abstract
Natural transformation is the process by which bacteria take up genetic material from their environment and integrate it into their genome by homologous recombination. It represents one mode of horizontal gene transfer and contributes to the spread of traits like antibiotic resistance. In Vibrio cholerae, a type IVa pilus (T4aP) is thought to facilitate natural transformation by extending from the cell surface, binding to exogenous DNA, and retracting to thread this DNA through the outer membrane secretin, PilQ. Here, we use a functional tagged allele of VcPilQ purified from native V. cholerae cells to determine the cryoEM structure of the VcPilQ secretin in amphipol to ~2.7 Å. We use bioinformatics to examine the domain architecture and gene neighborhood of T4aP secretins in Proteobacteria in comparison with VcPilQ. This structure highlights differences in the architecture of the T4aP secretin from the type II and type III secretion system secretins. Based on our cryoEM structure, we design a series of mutants to reversibly regulate VcPilQ gate dynamics. These experiments support the idea of VcPilQ as a potential druggable target and provide insight into the channel that DNA likely traverses to promote the spread of antibiotic resistance via horizontal gene transfer by natural transformation.
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Affiliation(s)
- Sara J Weaver
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA, 91125, USA.,Howard Hughes Medical Institute, David Geffen School of Medicine, Departments of Biological Chemistry and Physiology, University of California Los Angeles, 615 Charles E Young Drive South, Los Angeles, CA, 90095, USA
| | - Davi R Ortega
- Division of Biology and Biological Engineering and Howard Hughes Medical Institute, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA, 91125, USA
| | - Matthew H Sazinsky
- Department of Chemistry, Pomona College, 333N. College Way, Claremont, CA, 91711, USA
| | - Triana N Dalia
- Department of Biology, Indiana University, 107S. Indiana Avenue, Bloomington, IN, 47405, USA
| | - Ankur B Dalia
- Department of Biology, Indiana University, 107S. Indiana Avenue, Bloomington, IN, 47405, USA
| | - Grant J Jensen
- Division of Biology and Biological Engineering and Howard Hughes Medical Institute, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA, 91125, USA.
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18
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Miletic S, Goessweiner-Mohr N, Marlovits TC. The Structure of the Type III Secretion System Needle Complex. Curr Top Microbiol Immunol 2020; 427:67-90. [PMID: 31667599 DOI: 10.1007/82_2019_178] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The type III secretion system (T3SS) is an essential virulence factor of many pathogenic bacterial species including Salmonella, Yersinia, Shigella and enteropathogenic Escherichia coli (EPEC). It is an intricate molecular machine that spans the bacterial membranes and injects effector proteins into target host cells, enabling bacterial infection. The T3SS needle complex comprises of proteinaceous rings supporting a needle filament which extends out into the extracellular environment. It serves as the central conduit for translocating effector proteins. Multiple laboratories have dedicated a remarkable effort to decipher the structure and function of the needle complex. A combination of structural biology techniques such as cryo-electron microscopy (cryoEM), X-ray crystallography, nuclear magnetic resonance (NMR) spectroscopy and computer modelling have been utilized to study different structural components at progressively higher resolutions. This chapter will provide an overview of the structural details of the T3SS needle complex, shedding light on this essential component of this fascinating bacterial system.
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Affiliation(s)
- Sean Miletic
- Center for Structural Systems Biology, Institute for Structural and Systems Biology, Universitätsklinikum Hamburg-Eppendorf, 85 Notkestraße, Hamburg, 22607, Germany
| | | | - Thomas C Marlovits
- Center for Structural Systems Biology, Institute for Structural and Systems Biology, Universitätsklinikum Hamburg-Eppendorf, 85 Notkestraße, Hamburg, 22607, Germany.
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19
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The Evolution of Protein Secretion Systems by Co-option and Tinkering of Cellular Machineries. Trends Microbiol 2020; 28:372-386. [DOI: 10.1016/j.tim.2020.01.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2019] [Revised: 11/21/2019] [Accepted: 01/16/2020] [Indexed: 02/07/2023]
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20
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Molecular response of Deinococcus radiodurans to simulated microgravity explored by proteometabolomic approach. Sci Rep 2019; 9:18462. [PMID: 31804539 PMCID: PMC6895123 DOI: 10.1038/s41598-019-54742-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 11/19/2019] [Indexed: 12/21/2022] Open
Abstract
Regarding future space exploration missions and long-term exposure experiments, a detailed investigation of all factors present in the outer space environment and their effects on organisms of all life kingdoms is advantageous. Influenced by the multiple factors of outer space, the extremophilic bacterium Deinococcus radiodurans has been long-termly exposed outside the International Space Station in frames of the Tanpopo orbital mission. The study presented here aims to elucidate molecular key components in D. radiodurans, which are responsible for recognition and adaptation to simulated microgravity. D. radiodurans cultures were grown for two days on plates in a fast-rotating 2-D clinostat to minimize sedimentation, thus simulating reduced gravity conditions. Subsequently, metabolites and proteins were extracted and measured with mass spectrometry-based techniques. Our results emphasize the importance of certain signal transducer proteins, which showed higher abundances in cells grown under reduced gravity. These proteins activate a cellular signal cascade, which leads to differences in gene expressions. Proteins involved in stress response, repair mechanisms and proteins connected to the extracellular milieu and the cell envelope showed an increased abundance under simulated microgravity. Focusing on the expression of these proteins might present a strategy of cells to adapt to microgravity conditions.
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21
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Natarajan J, Moitra A, Zabel S, Singh N, Wagner S, Rapaport D. Yeast can express and assemble bacterial secretins in the mitochondrial outer membrane. MICROBIAL CELL 2019; 7:15-27. [PMID: 31921930 PMCID: PMC6946019 DOI: 10.15698/mic2020.01.703] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Secretins form large multimeric pores in the outer membrane (OM) of Gram-negative bacteria. These pores are part of type II and III secretion systems (T2SS and T3SS, respectively) and are crucial for pathogenicity. Recent structural studies indicate that secretins form a structure rich in β-strands. However, little is known about the mechanism by which secretins assemble into the OM. Based on the conservation of the biogenesis of β-barrel proteins in bacteria and mitochondria, we used yeast cells as a model system to study the assembly process of secretins. To that end, we analyzed the biogenesis of PulD (T2SS), SsaC (T3SS) and InvG (T3SS) in wild type cells or in cells mutated for known mitochondrial import and assembly factors. Our results suggest that secretins can be expressed in yeast cells, where they are enriched in the mitochondrial fraction. Interestingly, deletion of mitochondrial import receptors like Tom20 and Tom70 reduces the mitochondrial association of PulD but does not affect that of InvG. SsaC shows another dependency pattern and its membrane assembly is enhanced by the absence of Tom70 and compromised in cells lacking Tom20 or the topogenesis of outer membrane β-barrel proteins (TOB) complex component, Mas37. Collectively, these findings suggest that various secretins can follow different pathways to assemble into the bacterial OM.
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Affiliation(s)
- Janani Natarajan
- Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany
| | - Anasuya Moitra
- Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany
| | - Sussanne Zabel
- Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany.,Current address: Center for Bioinformatics (ZBIT), University of Tübingen, Tübingen, Germany
| | - Nidhi Singh
- Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Tübingen, Germany
| | - Samuel Wagner
- Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Tübingen, Germany.,German Center for Infection Research (DZIF), partner-site Tübingen, Tübingen, Germany
| | - Doron Rapaport
- Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany
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22
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Abstract
Case studies of the evolution of molecular machines remain scarce. One of the most diverse and widespread homologous families of machines is the type IV filament (TFF) superfamily, comprised of type IV pili, type II secretion systems (T2SSs), archaella, and other less-well-characterized families. These families have functions including twitching motility, effector export, rotary propulsion, nutrient uptake, DNA uptake, and even electrical conductance, but it is unclear how such diversity evolved from a common ancestor. In this issue, Denise and colleagues take a significant step toward understanding evolution of the TFF superfamily by determining a global phylogeny and using it to infer an evolutionary pathway. Results reveal that the superfamily predates the divergence of Bacteria and Archaea, and show how duplications, acquisitions, and losses coincide with changes in function. Surprises include that tight adherence (Tad) pili were horizontally acquired from Archaea and that T2SSs were relatively recently repurposed from type IV pili. Results also enable better understanding of the function of the ATPase family that powers the superfamily. The study highlights the role of tinkering by exaptation-the repurposing of pre-existing functions for new roles-in the diversification of molecular machines.
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Affiliation(s)
- Morgan Beeby
- Department of Life Sciences, Imperial College London, London, United Kingdom
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23
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DeAngelis CM, Nag D, Withey JH, Matson JS. Characterization of the Vibrio cholerae Phage Shock Protein Response. J Bacteriol 2019; 201:e00761-18. [PMID: 30858296 PMCID: PMC6597379 DOI: 10.1128/jb.00761-18] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Accepted: 02/26/2019] [Indexed: 12/25/2022] Open
Abstract
The phage shock protein (Psp) system is a stress response pathway that senses and responds to inner membrane damage. The genetic components of the Psp system are present in several clinically relevant Gram-negative bacteria, including Vibrio cholerae However, most of the current knowledge about the Psp response stems from in vitro studies in Escherichia coli and Yersinia enterocolitica In fact, the Psp response in V. cholerae has remained completely uncharacterized. In this study, we demonstrate that V. cholerae does have a functional Psp response system. We found that overexpression of GspD (EpsD), the type II secretion system secretin, induces the Psp response, whereas other V. cholerae secretins do not. In addition, we have identified several environmental conditions that induce this stress response. Our studies on the genetic regulation and induction of the Psp system in V. cholerae suggest that the key regulatory elements are conserved with those of other Gram-negative bacteria. While a psp null strain is fully capable of colonizing the infant mouse intestine, it exhibits a colonization defect in a zebrafish model, indicating that this response may be important for disease transmission in the environment. Overall, these studies provide an initial understanding of a stress response pathway that has not been previously investigated in V. choleraeIMPORTANCEVibrio cholerae leads a dual life cycle, as it can exist in the aquatic environment and colonize the human small intestine. In both life cycles, V. cholerae encounters a variety of stressful conditions, including fluctuating pH and temperature and exposure to other agents that may negatively affect cell envelope homeostasis. The phage shock protein (Psp) response is required to sense and respond to such insults in other bacteria but has remained unstudied in V. cholerae Interestingly, the Psp system has protein homologs, principally, PspA, in a number of bacterial clades as well as in archaea and plants. Therefore, our findings not only fill a gap in knowledge about an unstudied extracytoplasmic stress response in V. cholerae, but also may have far-reaching implications.
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Affiliation(s)
- Cara M DeAngelis
- Department of Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, Ohio, USA
| | - Dhrubajyoti Nag
- Department of Biochemistry, Microbiology, and Immunology, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Jeffrey H Withey
- Department of Biochemistry, Microbiology, and Immunology, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Jyl S Matson
- Department of Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, Ohio, USA
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24
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Natarajan J, Singh N, Rapaport D. Assembly and targeting of secretins in the bacterial outer membrane. Int J Med Microbiol 2019; 309:151322. [PMID: 31262642 DOI: 10.1016/j.ijmm.2019.06.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 06/04/2019] [Accepted: 06/18/2019] [Indexed: 11/20/2022] Open
Abstract
In Gram-negative bacteria, secretion of toxins ensure the survival of the bacterium. Such toxins are secreted by sophisticated multiprotein systems. The most conserved part in some of these secretion systems are components, called secretins, which form the outer membrane ring in these systems. Recent structural studies shed some light on the oligomeric organization of secretins. However, the mechanisms by which these proteins are targeted to the outer membrane and assemble there into ring structures are still not fully understood. This review discusses the various species-specific targeting and assembly pathways that are taken by secretins in order to form their functional oligomers.
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Affiliation(s)
- Janani Natarajan
- Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany.
| | - Nidhi Singh
- Interfaculty Institute of Microbiology and Infection Medicine (IMIT), Elfriede-Aulhorn-Str.6, 72076 Tübingen, Germany
| | - Doron Rapaport
- Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany
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25
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Denise R, Abby SS, Rocha EPC. Diversification of the type IV filament superfamily into machines for adhesion, protein secretion, DNA uptake, and motility. PLoS Biol 2019; 17:e3000390. [PMID: 31323028 PMCID: PMC6668835 DOI: 10.1371/journal.pbio.3000390] [Citation(s) in RCA: 83] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 07/31/2019] [Accepted: 07/03/2019] [Indexed: 12/21/2022] Open
Abstract
Processes of molecular innovation require tinkering and shifting in the function of existing genes. How this occurs in terms of molecular evolution at long evolutionary scales remains poorly understood. Here, we analyse the natural history of a vast group of membrane-associated molecular systems in Bacteria and Archaea-the type IV filament (TFF) superfamily-that diversified in systems involved in flagellar or twitching motility, adhesion, protein secretion, and DNA uptake. The phylogeny of the thousands of detected systems suggests they may have been present in the last universal common ancestor. From there, two lineages-a bacterial and an archaeal-diversified by multiple gene duplications, gene fissions and deletions, and accretion of novel components. Surprisingly, we find that the 'tight adherence' (Tad) systems originated from the interkingdom transfer from Archaea to Bacteria of a system resembling the 'EppA-dependent' (Epd) pilus and were associated with the acquisition of a secretin. The phylogeny and content of ancestral systems suggest that initial bacterial pili were engaged in cell motility and/or DNA uptake. In contrast, specialised protein secretion systems arose several times independently and much later in natural history. The functional diversification of the TFF superfamily was accompanied by genetic rearrangements with implications for genetic regulation and horizontal gene transfer: systems encoded in fewer loci were more frequently exchanged between taxa. This may have contributed to their rapid evolution and spread across Bacteria and Archaea. Hence, the evolutionary history of the superfamily reveals an impressive catalogue of molecular evolution mechanisms that resulted in remarkable functional innovation and specialisation from a relatively small set of components.
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Affiliation(s)
- Rémi Denise
- Microbial Evolutionary Genomics, Institut Pasteur, CNRS, UMR3525, Paris, France
- Sorbonne Université, Collège doctoral, Paris, France
| | - Sophie S. Abby
- Université Grenoble Alpes, CNRS, Grenoble INP, TIMC-IMAG, Grenoble, France
| | - Eduardo P. C. Rocha
- Microbial Evolutionary Genomics, Institut Pasteur, CNRS, UMR3525, Paris, France
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26
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Howard SP, Estrozi LF, Bertrand Q, Contreras-Martel C, Strozen T, Job V, Martins A, Fenel D, Schoehn G, Dessen A. Structure and assembly of pilotin-dependent and -independent secretins of the type II secretion system. PLoS Pathog 2019; 15:e1007731. [PMID: 31083688 PMCID: PMC6532946 DOI: 10.1371/journal.ppat.1007731] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 05/23/2019] [Accepted: 03/26/2019] [Indexed: 01/09/2023] Open
Abstract
The type II secretion system (T2SS) is a cell envelope-spanning macromolecular complex that is prevalent in Gram-negative bacterial species. It serves as the predominant virulence mechanism of many bacteria including those of the emerging human pathogens Vibrio vulnificus and Aeromonas hydrophila. The system is composed of a core set of highly conserved proteins that assemble an inner membrane platform, a periplasmic pseudopilus and an outer membrane complex termed the secretin. Localization and assembly of secretins in the outer membrane requires recognition of secretin monomers by two different partner systems: an inner membrane accessory complex or a highly sequence-diverse outer membrane lipoprotein, termed the pilotin. In this study, we addressed the question of differential secretin assembly mechanisms by using cryo-electron microscopy to determine the structures of the secretins from A. hydrophila (pilotin-independent ExeD) and V. vulnificus (pilotin-dependent EpsD). These structures, at approximately 3.5 Å resolution, reveal pentadecameric stoichiometries and C-terminal regions that carry a signature motif in the case of a pilotin-dependent assembly mechanism. We solved the crystal structure of the V. vulnificus EpsS pilotin and confirmed the importance of the signature motif for pilotin-dependent secretin assembly by performing modelling with the C-terminus of EpsD. We also show that secretin assembly is essential for membrane integrity and toxin secretion in V. vulnificus and establish that EpsD requires the coordinated activity of both the accessory complex EpsAB and the pilotin EpsS for full assembly and T2SS function. In contrast, mutation of the region of the S-domain that is normally the site of pilotin interactions has little effect on assembly or function of the ExeD secretin. Since secretins are essential outer membrane channels present in a variety of secretion systems, these results provide a structural and functional basis for understanding the key assembly steps for different members of this vast pore-forming family of proteins.
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Affiliation(s)
- S. Peter Howard
- Dept. Biochemistry, Microbiology and Immunology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Leandro F. Estrozi
- Univ Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), Grenoble, France
| | - Quentin Bertrand
- Univ Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), Grenoble, France
| | | | - Timothy Strozen
- Dept. Biochemistry, Microbiology and Immunology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Viviana Job
- Univ Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), Grenoble, France
| | - Alexandre Martins
- Univ Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), Grenoble, France
| | - Daphna Fenel
- Univ Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), Grenoble, France
| | - Guy Schoehn
- Univ Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), Grenoble, France
| | - Andréa Dessen
- Univ Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), Grenoble, France
- Brazilian Biosciences National Laboratory (LNBio), CNPEM, Campinas, São Paulo, Brazil
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27
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Abstract
Bacteria employ a number of dedicated secretion systems to export proteins to the extracellular environment. Several of these comprise large complexes that assemble in and around the bacterial membrane(s) to form specialized channels through which only selected proteins are actively delivered. Although typically associated with bacterial pathogenicity, a specialized variant of these secretion systems has been proposed to play a central part in bacterial sporulation, a primitive protective process that allows starving cells to form spores that survive in extreme environments. Following asymmetric division, the mother cell engulfs the forespore, leaving it surrounded by two bilayer membranes. During the engulfment process an essential channel apparatus is thought to cross both membranes to create a direct conduit between the mother cell and forespore. At least nine proteins are essential for channel formation, including SpoIIQ under forespore control and the eight SpoIIIA proteins (SpoIIIAA to -AH) under mother cell control. Presumed to form a core channel complex, several of these proteins share similarity with components of Gram-negative bacterial secretion systems, including the type II, III, and IV secretion systems and the flagellum. Based on these similarities it has been suggested that the sporulation channel represents a hybrid, secretion-like transport machinery. Recently, in-depth biochemical and structural characterization of the individual channel components accompanied by in vivo studies has further reinforced this model. Here we review and discuss these recent studies and suggest an updated model for the unique sporulation channel apparatus architecture.
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Kruse K, Salzer R, Averhoff B. The traffic ATPase PilF interacts with the inner membrane platform of the DNA translocator and type IV pili from Thermus thermophilus. FEBS Open Bio 2018; 9:4-17. [PMID: 30652069 PMCID: PMC6325625 DOI: 10.1002/2211-5463.12548] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 10/10/2018] [Accepted: 10/25/2018] [Indexed: 12/20/2022] Open
Abstract
A major driving force for the adaptation of bacteria to changing environments is the uptake of naked DNA from the environment by natural transformation, which allows the acquisition of new capabilities. Uptake of the high molecular weight DNA is mediated by a complex transport machinery that spans the entire cell periphery. This DNA translocator catalyzes the binding and splitting of double‐stranded DNA and translocation of single‐stranded DNA into the cytoplasm, where it is recombined with the chromosome. The thermophilic bacterium Thermus thermophilus exhibits the highest transformation frequencies reported and is a model system to analyze the structure and function of this macromolecular transport machinery. Transport activity is powered by the traffic ATPase PilF, a soluble protein that forms hexameric complexes. Here, we demonstrate that PilF physically binds to an inner membrane assembly platform of the DNA translocator, comprising PilMNO, via the ATP‐binding protein PilM. Binding to PilMNO or PilMN stimulates the ATPase activity of PilF ~ 2‐fold, whereas there is no stimulation when binding to PilM or PilN alone. A PilMK26A variant defective in ATP binding still binds PilF and, together with PilN, stimulates PilF‐mediated ATPase activity. PilF is unique in having three conserved GSPII (general secretory pathway II) domains (A–C) at its N terminus. Deletion analyses revealed that none of the GSPII domains is essential for binding PilMN, but GSPIIC is essential for PilMN‐mediated stimulation of ATP hydrolysis by PilF. Our data suggest that PilM is a coupling protein that physically and functionally connects the soluble motor ATPase PilF to the DNA translocator via the PilMNO assembly platform.
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Affiliation(s)
- Kerstin Kruse
- Molecular Microbiology & Bioenergetics Institute of Molecular Biosciences Goethe University Frankfurt Germany
| | - Ralf Salzer
- Molecular Microbiology & Bioenergetics Institute of Molecular Biosciences Goethe University Frankfurt Germany.,Present address: Structural Studies Division Medical Research Council - Laboratory of Molecular Biology Cambridge Biomedical Campus, Francis Crick Ave Cambridge CB2 OQH UK
| | - Beate Averhoff
- Molecular Microbiology & Bioenergetics Institute of Molecular Biosciences Goethe University Frankfurt Germany
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29
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Gadwal S, Johnson TL, Remmer H, Sandkvist M. C-terminal processing of GlyGly-CTERM containing proteins by rhombosortase in Vibrio cholerae. PLoS Pathog 2018; 14:e1007341. [PMID: 30352106 PMCID: PMC6219818 DOI: 10.1371/journal.ppat.1007341] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Revised: 11/06/2018] [Accepted: 09/17/2018] [Indexed: 11/18/2022] Open
Abstract
Vibrio cholerae and a subset of other Gram-negative bacteria, including Acinetobacter baumannii, express proteins with a C-terminal tripartite domain called GlyGly-CTERM, which consists of a motif rich in glycines and serines, followed by a hydrophobic region and positively charged residues. Here we show that VesB, a V. cholerae serine protease, requires the GlyGly-CTERM domain, the intramembrane rhomboid-like protease rhombosortase, and the type II secretion system (T2SS) for localization at the cell surface. VesB is cleaved by rhombosortase to expose the second glycine residue of the GlyGly-CTERM motif, which is then conjugated to a glycerophosphoethanolamine-containing moiety prior to engagement with the T2SS and outer membrane translocation. In support of this, VesB accumulates intracellularly in the absence of the T2SS, and surface-associated VesB activity is no longer detected when the rhombosortase gene is inactivated. In turn, when VesB is expressed without an intact GlyGly-CTERM domain, VesB is released to the extracellular milieu by the T2SS and does not accumulate on the cell surface. Collectively, our findings suggest that the posttranslational modification of the GlyGly-CTERM domain is essential for cell surface localization of VesB and other proteins expressed with this tripartite extension.
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Affiliation(s)
- Shilpa Gadwal
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, United States of America
| | - Tanya L. Johnson
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, United States of America
- Department of Chemistry, Eastern Michigan University, Ypsilanti, MI, United States of America
| | - Henriette Remmer
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, United States of America
| | - Maria Sandkvist
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, United States of America
- * E-mail:
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Hu J, Worrall LJ, Hong C, Vuckovic M, Atkinson CE, Caveney N, Yu Z, Strynadka NCJ. Cryo-EM analysis of the T3S injectisome reveals the structure of the needle and open secretin. Nat Commun 2018; 9:3840. [PMID: 30242280 PMCID: PMC6155069 DOI: 10.1038/s41467-018-06298-8] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Accepted: 07/20/2018] [Indexed: 11/09/2022] Open
Abstract
The bacterial type III secretion system, or injectisome, is a syringe shaped nanomachine essential for the virulence of many disease causing Gram-negative bacteria. At the core of the injectisome structure is the needle complex, a continuous channel formed by the highly oligomerized inner and outer membrane hollow rings and a polymerized helical needle filament which spans through and projects into the infected host cell. Here we present the near-atomic resolution structure of a needle complex from the prototypical Salmonella Typhimurium SPI-1 type III secretion system, with local masking protocols allowing for model building and refinement of the major membrane spanning components of the needle complex base in addition to an isolated needle filament. This work provides significant insight into injectisome structure and assembly and importantly captures the molecular basis for substrate induced gating in the giant outer membrane secretin portal family.
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Affiliation(s)
- J Hu
- Department of Biochemistry and Molecular Biology and the Centre for Blood Research, University of British Columbia, Vancouver, V6T 1Z3, BC, Canada
| | - L J Worrall
- Department of Biochemistry and Molecular Biology and the Centre for Blood Research, University of British Columbia, Vancouver, V6T 1Z3, BC, Canada
- HRMEM facility, University of British Columbia, Vancouver, V6T 1Z3, BC, Canada
| | - C Hong
- CryoEM Shared Resources, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, 20147, VA, USA
| | - M Vuckovic
- Department of Biochemistry and Molecular Biology and the Centre for Blood Research, University of British Columbia, Vancouver, V6T 1Z3, BC, Canada
| | - C E Atkinson
- Department of Biochemistry and Molecular Biology and the Centre for Blood Research, University of British Columbia, Vancouver, V6T 1Z3, BC, Canada
- HRMEM facility, University of British Columbia, Vancouver, V6T 1Z3, BC, Canada
| | - N Caveney
- Department of Biochemistry and Molecular Biology and the Centre for Blood Research, University of British Columbia, Vancouver, V6T 1Z3, BC, Canada
| | - Z Yu
- CryoEM Shared Resources, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, 20147, VA, USA
| | - N C J Strynadka
- Department of Biochemistry and Molecular Biology and the Centre for Blood Research, University of British Columbia, Vancouver, V6T 1Z3, BC, Canada.
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31
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Structural insight into the assembly of the type II secretion system pilotin–secretin complex from enterotoxigenic Escherichia coli. Nat Microbiol 2018; 3:581-587. [DOI: 10.1038/s41564-018-0148-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 03/07/2018] [Indexed: 12/29/2022]
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32
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Abstract
Bacterial secretins are outer membrane proteins that provide a path for secreted proteins to access the cell exterior/surface. They are one of the core components of secretion machines and are found in type II and type III secretion systems (T2SS and T3SS, respectively). The secretins comprise giant ring-shaped homo-oligomers whose precise atomic organization was only recently deciphered thanks to spectacular developments in cryo-electron microscopy (cryo-EM) imaging techniques.
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Affiliation(s)
- Alain Filloux
- Imperial College London, Department of Life Sciences, MRC-CMBI, London, United Kingdom
| | - Romé Voulhoux
- Aix Marseille University, CNRS, IMM, LISM, Marseille, France
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33
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Structure and Membrane Topography of the Vibrio-Type Secretin Complex from the Type 2 Secretion System of Enteropathogenic Escherichia coli. J Bacteriol 2018; 200:JB.00521-17. [PMID: 29084860 DOI: 10.1128/jb.00521-17] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 10/25/2017] [Indexed: 12/11/2022] Open
Abstract
The β-barrel assembly machinery (BAM) complex is the core machinery for the assembly of β-barrel membrane proteins, and inhibition of BAM complex activity is lethal to bacteria. Discovery of integral membrane proteins that are key to pathogenesis and yet do not require assistance from the BAM complex raises the question of how these proteins assemble into bacterial outer membranes. Here, we address this question through a structural analysis of the type 2 secretion system (T2SS) secretin from enteropathogenic Escherichia coli O127:H6 strain E2348/69. Long β-strands assemble into a barrel extending 17 Å through and beyond the outer membrane, adding insight to how these extensive β-strands are assembled into the E. coli outer membrane. The substrate docking chamber of this secretin is shown to be sufficient to accommodate the substrate mucinase SteC.IMPORTANCE In order to cause disease, bacterial pathogens inhibit immune responses and induce pathology that will favor their replication and dissemination. In Gram-negative bacteria, these key attributes of pathogenesis depend on structures assembled into or onto the outer membrane. One of these is the T2SS. The Vibrio-type T2SS mediates cholera toxin secretion in Vibrio cholerae, and in Escherichia coli O127:H6 strain E2348/69, the same machinery mediates secretion of the mucinases that enable the pathogen to penetrate intestinal mucus and thereby establish deadly infections.
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D'Imprima E, Salzer R, Bhaskara RM, Sánchez R, Rose I, Kirchner L, Hummer G, Kühlbrandt W, Vonck J, Averhoff B. Cryo-EM structure of the bifunctional secretin complex of Thermus thermophilus. eLife 2017; 6. [PMID: 29280731 PMCID: PMC5745081 DOI: 10.7554/elife.30483] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 12/13/2017] [Indexed: 11/13/2022] Open
Abstract
Secretins form multimeric channels across the outer membrane of Gram-negative bacteria that mediate the import or export of substrates and/or extrusion of type IV pili. The secretin complex of Thermus thermophilus is an oligomer of the 757-residue PilQ protein, essential for DNA uptake and pilus extrusion. Here, we present the cryo-EM structure of this bifunctional complex at a resolution of ~7 Å using a new reconstruction protocol. Thirteen protomers form a large periplasmic domain of six stacked rings and a secretin domain in the outer membrane. A homology model of the PilQ protein was fitted into the cryo-EM map. A crown-like structure outside the outer membrane capping the secretin was found not to be part of PilQ. Mutations in the secretin domain disrupted the crown and abolished DNA uptake, suggesting a central role of the crown in natural transformation.
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Affiliation(s)
- Edoardo D'Imprima
- Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt, Germany
| | - Ralf Salzer
- Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Goethe University Frankfurt, Frankfurt, Germany
| | - Ramachandra M Bhaskara
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Frankfurt, Germany
| | - Ricardo Sánchez
- Sofja Kovalevskaja Group, Max Planck Institute of Biophysics, Frankfurt, Germany
| | - Ilona Rose
- Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Goethe University Frankfurt, Frankfurt, Germany
| | - Lennart Kirchner
- Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Goethe University Frankfurt, Frankfurt, Germany
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Frankfurt, Germany.,Institute of Biophysics, Goethe University Frankfurt, Frankfurt, Germany
| | - Werner Kühlbrandt
- Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt, Germany
| | - Janet Vonck
- Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt, Germany
| | - Beate Averhoff
- Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Goethe University Frankfurt, Frankfurt, Germany
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Unraveling the Self-Assembly of the Pseudomonas aeruginosa XcpQ Secretin Periplasmic Domain Provides New Molecular Insights into Type II Secretion System Secreton Architecture and Dynamics. mBio 2017; 8:mBio.01185-17. [PMID: 29042493 PMCID: PMC5646246 DOI: 10.1128/mbio.01185-17] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The type II secretion system (T2SS) releases large folded exoproteins across the envelope of many Gram-negative pathogens. This secretion process therefore requires specific gating, interacting, and dynamics properties mainly operated by a bipartite outer membrane channel called secretin. We have a good understanding of the structure-function relationship of the pore-forming C-terminal domain of secretins. In contrast, the high flexibility of their periplasmic N-terminal domain has been an obstacle in obtaining the detailed structural information required to uncover its molecular function. In Pseudomonas aeruginosa, the Xcp T2SS plays an important role in bacterial virulence by its capacity to deliver a large panel of toxins and degradative enzymes into the surrounding environment. Here, we revealed that the N-terminal domain of XcpQ secretin spontaneously self-assembled into a hexamer of dimers independently of its C-terminal domain. Furthermore, and by using multidisciplinary approaches, we elucidate the structural organization of the XcpQ N domain and demonstrate that secretin flexibility at interdimer interfaces is mandatory for its function. Bacterial secretins are large homooligomeric proteins constituting the outer membrane pore-forming element of several envelope-embedded nanomachines essential in bacterial survival and pathogenicity. They comprise a well-defined membrane-embedded C-terminal domain and a modular periplasmic N-terminal domain involved in substrate recruitment and connection with inner membrane components. We are studying the XcpQ secretin of the T2SS present in the pathogenic bacterium Pseudomonas aeruginosa. Our data highlight the ability of the XcpQ N-terminal domain to spontaneously oligomerize into a hexamer of dimers. Further in vivo experiments revealed that this domain adopts different conformations essential for the T2SS secretion process. These findings provide new insights into the functional understanding of bacterial T2SS secretins.
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36
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Psp Stress Response Proteins Form a Complex with Mislocalized Secretins in the Yersinia enterocolitica Cytoplasmic Membrane. mBio 2017; 8:mBio.01088-17. [PMID: 28900025 PMCID: PMC5596341 DOI: 10.1128/mbio.01088-17] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The bacterial phage shock protein system (Psp) is a conserved extracytoplasmic stress response that is essential for the virulence of some pathogens, including Yersinia enterocolitica It is induced by events that can compromise inner membrane (IM) integrity, including the mislocalization of outer membrane pore-forming proteins called secretins. In the absence of the Psp system, secretin mislocalization permeabilizes the IM and causes rapid cell death. The Psp proteins PspB and PspC form an integral IM complex with two independent roles. First, the PspBC complex is required to activate the Psp response in response to some inducing triggers, including a mislocalized secretin. Second, PspBC are sufficient to counteract mislocalized secretin toxicity. Remarkably, secretin mislocalization into the IM induces psp gene expression without significantly affecting the expression of any other genes. Furthermore, psp null strains are killed by mislocalized secretins, whereas no other null mutants have been found to share this specific secretin sensitivity. This suggests an exquisitely specific relationship between secretins and the Psp system, but there has been no mechanism described to explain this. In this study, we addressed this deficiency by using a coimmunoprecipitation approach to show that the Psp proteins form a specific complex with mislocalized secretins in the Y. enterocolitica IM. Importantly, analysis of different secretin mutant proteins also revealed that this interaction is absolutely dependent on a secretin adopting a multimeric state. Therefore, the Psp system has evolved with the ability to detect and detoxify dangerous secretin multimers while ignoring the presence of innocuous monomers.IMPORTANCE The phage shock protein (Psp) response has been linked to important phenotypes in diverse bacteria, including those related to antibiotic resistance, biofilm formation, and virulence. This has generated widespread interest in understanding various aspects of its function. Outer membrane secretin proteins are essential components of export systems required for the virulence of many bacterial pathogens. However, secretins can mislocalize into the inner membrane, and this induces the Psp response in a highly specific manner and kills Psp-defective strains with similar specificity. There has been no mechanism described to explain this exquisitely specific relationship between secretins and the Psp system. Therefore, this study provides a critical advance by discovering that Psp effector proteins form a complex with secretins in the Yersinia enterocolitica inner membrane. Remarkably, this interaction is absolutely dependent on a secretin adopting its multimeric state. Therefore, the Psp system detects and detoxifies dangerous secretin multimers, while ignoring the presence of innocuous secretin monomers.
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37
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Near-atomic resolution cryoelectron microscopy structure of the 30-fold homooligomeric SpoIIIAG channel essential to spore formation in Bacillus subtilis. Proc Natl Acad Sci U S A 2017; 114:E7073-E7081. [PMID: 28784753 DOI: 10.1073/pnas.1704310114] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Bacterial sporulation allows starving cells to differentiate into metabolically dormant spores that can survive extreme conditions. Following asymmetric division, the mother cell engulfs the forespore, surrounding it with two bilayer membranes. During the engulfment process, an essential channel, the so-called feeding tube apparatus, is thought to cross both membranes to create a direct conduit between the mother cell and the forespore. At least nine proteins are required to create this channel, including SpoIIQ and SpoIIIAA-AH. Here, we present the near-atomic resolution structure of one of these proteins, SpoIIIAG, determined by single-particle cryo-EM. A 3D reconstruction revealed that SpoIIIAG assembles into a large and stable 30-fold symmetric complex with a unique mushroom-like architecture. The complex is collectively composed of three distinctive circular structures: a 60-stranded vertical β-barrel that forms a large inner channel encircled by two concentric rings, one β-mediated and the other formed by repeats of a ring-building motif (RBM) common to the architecture of various dual membrane secretion systems of distinct function. Our near-atomic resolution structure clearly shows that SpoIIIAG exhibits a unique and dramatic adaptation of the RBM fold with a unique β-triangle insertion that assembles into the prominent channel, the dimensions of which suggest the potential passage of large macromolecules between the mother cell and forespore during the feeding process. Indeed, mutation of residues located at key interfaces between monomers of this RBM resulted in severe defects both in vivo and in vitro, providing additional support for this unprecedented structure.
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Leong CG, Bloomfield RA, Boyd CA, Dornbusch AJ, Lieber L, Liu F, Owen A, Slay E, Lang KM, Lostroh CP. The role of core and accessory type IV pilus genes in natural transformation and twitching motility in the bacterium Acinetobacter baylyi. PLoS One 2017; 12:e0182139. [PMID: 28771515 PMCID: PMC5542475 DOI: 10.1371/journal.pone.0182139] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 07/12/2017] [Indexed: 11/21/2022] Open
Abstract
Here we present an examination of type IV pilus genes associated with competence and twitching in the bacterium Acinetobacter baylyi (strain ADP1, BD413). We used bioinformatics to identify potential competence and twitching genes and their operons. We measured the competence and twitching phenotypes of the bioinformatically-identified genes. These results demonstrate that competence and twitching in A. baylyi both rely upon a core of the same type IV pilus proteins. The core includes the inner membrane assembly platform (PilC), a periplasmic assemblage connecting the inner membrane assembly platform to the secretin (ComM), a secretin (ComQ) and its associated pilotin (PilF) that assists with secretin assembly and localization, both cytoplasmic pilus retraction ATPases (PilU, PilT), and pilins (ComP, ComB, PilX). Proteins not needed for both competence and twitching are instead found to specialize in either of the two traits. The pilins are varied in their specialization with some required for either competence (FimT) and others for twitching (ComE). The protein that transports DNA across the inner membrane (ComA) specializes in competence, while signal transduction proteins (PilG, PilS, and PilR) specialize in twitching. Taken together our results suggest that the function of accessory proteins should not be based on homology alone. In addition the results suggest that in A. baylyi the mechanisms of natural transformation and twitching are mediated by the same set of core Type IV pilus proteins with distinct specialized proteins required for each phenotype. Finally, since competence requires multiple pilins as well as both pilus retraction motors PilU and PilT, this suggests that A. baylyi employs a pilus in natural transformation.
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Affiliation(s)
- Colleen G. Leong
- Department of Molecular Biology, Colorado College, Colorado Springs, Colorado, United States of America
| | - Rebecca A. Bloomfield
- Department of Molecular Biology, Colorado College, Colorado Springs, Colorado, United States of America
| | - Caroline A. Boyd
- Department of Molecular Biology, Colorado College, Colorado Springs, Colorado, United States of America
| | - Amber J. Dornbusch
- Department of Molecular Biology, Colorado College, Colorado Springs, Colorado, United States of America
| | - Leah Lieber
- Department of Molecular Biology, Colorado College, Colorado Springs, Colorado, United States of America
| | - Flora Liu
- Department of Molecular Biology, Colorado College, Colorado Springs, Colorado, United States of America
| | - Amie Owen
- Department of Molecular Biology, Colorado College, Colorado Springs, Colorado, United States of America
| | - Erin Slay
- Department of Molecular Biology, Colorado College, Colorado Springs, Colorado, United States of America
| | - Kristine M. Lang
- Department of Physics, Colorado College, Colorado Springs, Colorado, United States of America
| | - C. Phoebe Lostroh
- Department of Molecular Biology, Colorado College, Colorado Springs, Colorado, United States of America
- * E-mail:
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Gu S, Shevchik VE, Shaw R, Pickersgill RW, Garnett JA. The role of intrinsic disorder and dynamics in the assembly and function of the type II secretion system. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2017; 1865:1255-1266. [PMID: 28733198 DOI: 10.1016/j.bbapap.2017.07.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 07/02/2017] [Accepted: 07/17/2017] [Indexed: 10/19/2022]
Abstract
Many Gram-negative commensal and pathogenic bacteria use a type II secretion system (T2SS) to transport proteins out of the cell. These exported proteins or substrates play a major role in toxin delivery, maintaining biofilms, replication in the host and subversion of host immune responses to infection. We review the current structural and functional work on this system and argue that intrinsically disordered regions and protein dynamics are central for assembly, exo-protein recognition, and secretion competence of the T2SS. The central role of intrinsic disorder-order transitions in these processes may be a particular feature of type II secretion.
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Affiliation(s)
- Shuang Gu
- Queen Mary University of London, School of Biological and Chemical Sciences, London E1 4NS, United Kingdom
| | - Vladimir E Shevchik
- Université de Lyon, F-69003, Université Lyon 1, Lyon, F-69622, INSA-Lyon, Villeurbanne F-69621, CNRS, UMR5240, Microbiologie Adaptation et Pathogénie, Lyon F-69622, France
| | - Rosie Shaw
- Queen Mary University of London, School of Biological and Chemical Sciences, London E1 4NS, United Kingdom
| | - Richard W Pickersgill
- Queen Mary University of London, School of Biological and Chemical Sciences, London E1 4NS, United Kingdom.
| | - James A Garnett
- Queen Mary University of London, School of Biological and Chemical Sciences, London E1 4NS, United Kingdom.
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40
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Reconstitution of a minimal machinery capable of assembling periplasmic type IV pili. Proc Natl Acad Sci U S A 2017; 114:E4978-E4986. [PMID: 28588140 DOI: 10.1073/pnas.1618539114] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Type IV pili (Tfp), which are key virulence factors in many bacterial pathogens, define a large group of multipurpose filamentous nanomachines widespread in Bacteria and Archaea. Tfp biogenesis is a complex multistep process, which relies on macromolecular assemblies composed of 15 conserved proteins in model gram-negative species. To improve our limited understanding of the molecular mechanisms of filament assembly, we have used a synthetic biology approach to reconstitute, in a nonnative heterologous host, a minimal machinery capable of building Tfp. Here we show that eight synthetic genes are sufficient to promote filament assembly and that the corresponding proteins form a macromolecular complex at the cytoplasmic membrane, which we have purified and characterized biochemically. Our results contribute to a better mechanistic understanding of the assembly of remarkable dynamic filaments nearly ubiquitous in prokaryotes.
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41
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Abstract
Pili are crucial virulence factors for many Gram-negative pathogens. These surface structures provide bacteria with a link to their external environments by enabling them to interact with, and attach to, host cells, other surfaces or each other, or by providing a conduit for secretion. Recent high-resolution structures of pilus filaments and the machineries that produce them, namely chaperone-usher pili, type IV pili, conjugative type IV secretion pili and type V pili, are beginning to explain some of the intriguing biological properties that pili exhibit, such as the ability of chaperone-usher pili and type IV pili to stretch in response to external forces. By contrast, conjugative pili provide a conduit for the exchange of genetic information, and recent high-resolution structures have revealed an integral association between the pilin subunit and a phospholipid molecule, which may facilitate DNA transport. In addition, progress in the area of cryo-electron tomography has provided a glimpse of the overall architecture of the type IV pilus machinery. In this Review, we examine recent advances in our structural understanding of various Gram-negative pilus systems and discuss their functional implications.
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42
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Alterations in Peptidoglycan Cross-Linking Suppress the Secretin Assembly Defect Caused by Mutation of GspA in the Type II Secretion System. J Bacteriol 2017; 199:JB.00617-16. [PMID: 28138102 DOI: 10.1128/jb.00617-16] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2016] [Accepted: 01/23/2017] [Indexed: 12/22/2022] Open
Abstract
In Gram-negative bacteria, the peptidoglycan (PG) cell wall is a significant structural barrier for outer membrane protein assembly. In Aeromonas hydrophila, outer membrane multimerization of the type II secretion system (T2SS) secretin ExeD requires the function of the inner membrane assembly factor complex ExeAB. The putative mechanism of the complex involves the reorganization of PG and localization of ExeD, whereby ExeA functions by interacting with PG to form a site for secretin assembly and ExeB forms an interaction with ExeD. This mechanism led us to hypothesize that increasing the pore size of PG would circumvent the requirement for ExeA in the assembly of the ExeD secretin. Growth of A. hydrophila in 270 mM Gly reduced PG cross-links by approximately 30% and led to the suppression of secretin assembly defects in exeA strains and in those expressing ExeA mutants by enabling localization of the secretin in the outer membrane. We also established a heterologous ExeD assembly system in Escherichia coli and showed that ExeAB and ExeC are the only A. hydrophila proteins required for the assembly of the ExeD secretin in E. coli and that ExeAB-independent assembly of ExeD can occur upon overexpression of the d,d-carboxypeptidase PBP 5. These results support an assembly model in which, upon binding to PG, ExeA induces multimerization and pore formation in the sacculus, which enables ExeD monomers to interact with ExeB and assemble into a secretin that both is inserted in the outer membrane and crosses the PG layer to interact with the inner membrane platform of the T2SS.IMPORTANCE The PG layer imposes a strict structural impediment for the assembly of macromolecular structures that span the cell envelope and serve as virulence factors in Gram-negative species. This work revealed that by decreasing PG cross-linking by growth in Gly, the absolute requirement for the PG-binding activity of ExeA in the assembly of the ExeD secretin was alleviated in A. hydrophila In a heterologous assembly model in E. coli, expression of the carboxypeptidase PBP 5 could relieve the requirement for ExeAB in the assembly of the ExeD secretin. These results provide some mechanistic details of the ExeAB assembly complex function, in which the PG-binding and oligomerization functions of ExeAB are used to create a pore in the PG that is required for secretin assembly.
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Three-Dimensional Structure of the Ultraoligotrophic Marine Bacterium "Candidatus Pelagibacter ubique". Appl Environ Microbiol 2017; 83:AEM.02807-16. [PMID: 27836840 DOI: 10.1128/aem.02807-16] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Accepted: 11/09/2016] [Indexed: 11/20/2022] Open
Abstract
SAR11 bacteria are small, heterotrophic, marine alphaproteobacteria found throughout the oceans. They thrive at the low nutrient concentrations typical of open ocean conditions, although the adaptations required for life under those conditions are not well understood. To illuminate this issue, we used cryo-electron tomography to study "Candidatus Pelagibacter ubique" strain HTCC1062, a member of the SAR11 clade. Our results revealed its cellular dimensions and details of its intracellular organization. Frozen-hydrated cells, which were preserved in a life-like state, had an average cell volume (enclosed by the outer membrane) of 0.037 ± 0.011 μm3 Strikingly, the periplasmic space occupied ∼20% to 50% of the total cell volume in log-phase cells and ∼50% to 70% in stationary-phase cells. The nucleoid occupied the convex side of the crescent-shaped cells and the ribosomes predominantly occupied the concave side, at a relatively high concentration of 10,000 to 12,000 ribosomes/μm3 Outer membrane pore complexes, likely composed of PilQ, were frequently observed in both log-phase and stationary-phase cells. Long filaments, most likely type IV pili, were found on dividing cells. The physical dimensions, intracellular organization, and morphological changes throughout the life cycle of "Ca. Pelagibacter ubique" provide structural insights into the functional adaptions of these oligotrophic ultramicrobacteria to their habitat. IMPORTANCE Bacterioplankton of the SAR11 clade (Pelagibacterales) are of interest because of their global biogeochemical significance and because they appear to have been molded by unusual evolutionary circumstances that favor simplicity and efficiency. They have adapted to an ecosystem in which nutrient concentrations are near the extreme limits at which transport systems can function adequately, and they have evolved streamlined genomes to execute only functions essential for life. However, little is known about the actual size limitations and cellular features of living oligotrophic ultramicrobacteria. In this study, we have used cryo-electron tomography to obtain accurate physical information about the cellular architecture of "Candidatus Pelagibacter ubique," the first cultivated member of the SAR11 clade. These results provide foundational information for answering questions about the cell architecture and functions of these ultrasmall oligotrophic bacteria.
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Yan Z, Yin M, Xu D, Zhu Y, Li X. Structural insights into the secretin translocation channel in the type II secretion system. Nat Struct Mol Biol 2017; 24:177-183. [DOI: 10.1038/nsmb.3350] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2016] [Accepted: 12/06/2016] [Indexed: 12/31/2022]
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Rakonjac J, Russel M, Khanum S, Brooke SJ, Rajič M. Filamentous Phage: Structure and Biology. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1053:1-20. [PMID: 29549632 DOI: 10.1007/978-3-319-72077-7_1] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Ff filamentous phage (fd, M13 and f1) of Escherichia coli have been the workhorse of phage display technology for the past 30 years. Dominance of Ff over other bacteriophage in display technology stems from the titres that are about 100-fold higher than any other known phage, efficacious transformation ensuring large library size and superior stability of the virion at high temperatures, detergents and pH extremes, allowing broad range of biopanning conditions in screening phage display libraries. Due to the excellent understanding of infection and assembly requirements, Ff phage have also been at the core of phage-assisted continual protein evolution strategies (PACE). This chapter will give an overview of the Ff filamentous phage structure and biology, emphasizing those properties of the Ff phage life cycle and virion that are pertinent to phage display applications.
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Affiliation(s)
- Jasna Rakonjac
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand. .,Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, New Zealand.
| | | | - Sofia Khanum
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Sam J Brooke
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Marina Rajič
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand.,Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, New Zealand
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Interactions between the Cytoplasmic Domains of PspB and PspC Silence the Yersinia enterocolitica Phage Shock Protein Response. J Bacteriol 2016; 198:3367-3378. [PMID: 27698088 DOI: 10.1128/jb.00655-16] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 09/30/2016] [Indexed: 01/24/2023] Open
Abstract
The phage shock protein (Psp) system is a widely conserved cell envelope stress response that is essential for the virulence of some bacteria, including Yersinia enterocolitica Recruitment of PspA by the inner membrane PspB-PspC complex characterizes the activated state of this response. The PspB-PspC complex has been proposed to be a stress-responsive switch, changing from an OFF to an ON state in response to an inducing stimulus. In the OFF state, PspA cannot access its binding site in the C-terminal cytoplasmic domain of PspC (PspCCT), because this site is bound to PspB. PspC has another cytoplasmic domain at its N-terminal end (PspCNT), which has been thought to play a role in maintaining the OFF state, because its removal causes constitutive activation. However, until now, this role has proved recalcitrant to experimental investigation. Here, we developed a combination of approaches to investigate the role of PspCNT in Y. enterocolitica Pulldown assays provided evidence that PspCNT mediates the interaction of PspC with the C-terminal cytoplasmic domain of PspB (PspBCT) in vitro Furthermore, site-specific oxidative cross-linking suggested that a PspCNT-PspBCT interaction occurs only under noninducing conditions in vivo Additional experiments indicated that mutations in pspC might cause constitutive activation by compromising this PspCNT binding site or by causing a conformational disturbance that repositions PspCNT in vivo These findings have provided the first insight into the regulatory function of the N-terminal cytoplasmic domain of PspC, revealing that its ability to participate in an inhibitory complex is essential to silencing the Psp response. IMPORTANCE The phage shock protein (Psp) response has generated widespread interest because it is linked to important phenotypes, including antibiotic resistance, biofilm formation, and virulence in a diverse group of bacteria. Therefore, achieving a comprehensive understanding of how this response is controlled at the molecular level has obvious significance. An integral inner membrane protein complex is believed to be a critical regulatory component that acts as a stress-responsive switch, but some essential characteristics of the switch states are poorly understood. This study provides an important advance by uncovering a new protein interaction domain within this membrane protein complex that is essential to silencing the Psp response in the absence of an inducing stimulus.
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Walsh SI, Craney A, Romesberg FE. Not just an antibiotic target: Exploring the role of type I signal peptidase in bacterial virulence. Bioorg Med Chem 2016; 24:6370-6378. [PMID: 27769673 PMCID: PMC5279723 DOI: 10.1016/j.bmc.2016.09.048] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 09/17/2016] [Accepted: 09/19/2016] [Indexed: 01/23/2023]
Abstract
The looming antibiotic crisis has prompted the development of new strategies towards fighting infection. Traditional antibiotics target bacterial processes essential for viability, whereas proposed antivirulence approaches rely on the inhibition of factors that are required only for the initiation and propagation of infection within a host. Although antivirulence compounds have yet to prove their efficacy in the clinic, bacterial signal peptidase I (SPase) represents an attractive target in that SPase inhibitors exhibit broad-spectrum antibiotic activity, but even at sub-MIC doses also impair the secretion of essential virulence factors. The potential consequences of SPase inhibition on bacterial virulence have not been thoroughly examined, and are explored within this review. In addition, we review growing evidence that SPase has relevant biological functions outside of mediating secretion, and discuss how the inhibition of these functions may be clinically significant.
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Affiliation(s)
- Shawn I Walsh
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Arryn Craney
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Floyd E Romesberg
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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Worrall LJ, Hong C, Vuckovic M, Deng W, Bergeron JRC, Majewski DD, Huang RK, Spreter T, Finlay BB, Yu Z, Strynadka NCJ. Near-atomic-resolution cryo-EM analysis of the Salmonella T3S injectisome basal body. Nature 2016; 540:597-601. [DOI: 10.1038/nature20576] [Citation(s) in RCA: 109] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 10/25/2016] [Indexed: 12/17/2022]
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Abstract
Bacterial pathogens utilize a multitude of methods to invade mammalian hosts, damage tissue sites, and thwart the immune system from responding. One essential component of these strategies for many bacterial pathogens is the secretion of proteins across phospholipid membranes. Secreted proteins can play many roles in promoting bacterial virulence, from enhancing attachment to eukaryotic cells, to scavenging resources in an environmental niche, to directly intoxicating target cells and disrupting their functions. Many pathogens use dedicated protein secretion systems to secrete virulence factors from the cytosol of the bacteria into host cells or the host environment. In general, bacterial protein secretion apparatuses can be divided into classes, based on their structures, functions, and specificity. Some systems are conserved in all classes of bacteria and secrete a broad array of substrates, while others are only found in a small number of bacterial species and/or are specific to only one or a few proteins. In this chapter, we review the canonical features of several common bacterial protein secretion systems, as well as their roles in promoting the virulence of bacterial pathogens. Additionally, we address recent findings that indicate that the innate immune system of the host can detect and respond to the presence of protein secretion systems during mammalian infection.
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Guilvout I, Brier S, Chami M, Hourdel V, Francetic O, Pugsley AP, Chamot-Rooke J, Huysmans GHM. Prepore Stability Controls Productive Folding of the BAM-independent Multimeric Outer Membrane Secretin PulD. J Biol Chem 2016; 292:328-338. [PMID: 27903652 DOI: 10.1074/jbc.m116.759498] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 11/21/2016] [Indexed: 12/19/2022] Open
Abstract
Members of a group of multimeric secretion pores that assemble independently of any known membrane-embedded insertase in Gram-negative bacteria fold into a prepore before membrane-insertion occurs. The mechanisms and the energetics that drive the folding of these proteins are poorly understood. Here, equilibrium unfolding and hydrogen/deuterium exchange monitored by mass spectrometry indicated that a loss of 4-5 kJ/mol/protomer in the N3 domain that is peripheral to the membrane-spanning C domain in the dodecameric secretin PulD, the founding member of this class, prevents pore formation by destabilizing the prepore into a poorly structured dodecamer as visualized by electron microscopy. Formation of native PulD-multimers by mixing protomers that differ in N3 domain stability, suggested that the N3 domain forms a thermodynamic seal onto the prepore. This highlights the role of modest free energy changes in the folding of pre-integration forms of a hyperstable outer membrane complex and reveals a key driving force for assembly independently of the β-barrel assembly machinery.
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Affiliation(s)
- Ingrid Guilvout
- From the Molecular Genetics Unit, CNRS ERL 3526.,Laboratory of Macromolecular Systems and Signaling and
| | - Sébastien Brier
- Structural Mass Spectrometry and Proteomics Unit, CNRS UMR 3528, Institut Pasteur, 75724 Paris Cedex 15, France and
| | - Mohamed Chami
- the BioEM lab, Biozentrum, University of Basel, CH 4058 Basel, Switzerland
| | - Véronique Hourdel
- Structural Mass Spectrometry and Proteomics Unit, CNRS UMR 3528, Institut Pasteur, 75724 Paris Cedex 15, France and
| | - Olivera Francetic
- From the Molecular Genetics Unit, CNRS ERL 3526.,Laboratory of Macromolecular Systems and Signaling and
| | | | - Julia Chamot-Rooke
- Structural Mass Spectrometry and Proteomics Unit, CNRS UMR 3528, Institut Pasteur, 75724 Paris Cedex 15, France and
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