101
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Redefining the essential trafficking pathway for outer membrane lipoproteins. Proc Natl Acad Sci U S A 2017; 114:4769-4774. [PMID: 28416660 DOI: 10.1073/pnas.1702248114] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The outer membrane (OM) of Gram-negative bacteria is a permeability barrier and an intrinsic antibiotic resistance factor. Lipoproteins are OM components that function in cell wall synthesis, diverse secretion systems, and antibiotic efflux pumps. Moreover, each of the essential OM machines that assemble the barrier requires one or more lipoproteins. This dependence is thought to explain the essentiality of the periplasmic chaperone LolA and its OM receptor LolB that traffic lipoproteins to the OM. However, we show that in strains lacking substrates that are toxic when mislocalized, both LolA and LolB can be completely bypassed by activating an envelope stress response without compromising trafficking of essential lipoproteins. We identify the Cpx stress response as a monitor of lipoprotein trafficking tasked with protecting the cell from mislocalized lipoproteins. Moreover, our findings reveal that an alternate trafficking pathway exists that can, under certain conditions, bypass the functions of LolA and LolB, implying that these proteins do not perform any truly essential mechanistic steps in lipoprotein trafficking. Instead, these proteins' key function is to prevent lethal accumulation of mislocalized lipoproteins.
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102
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Bacterial thiol oxidoreductases - from basic research to new antibacterial strategies. Appl Microbiol Biotechnol 2017; 101:3977-3989. [PMID: 28409380 PMCID: PMC5403849 DOI: 10.1007/s00253-017-8291-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 04/03/2017] [Accepted: 04/04/2017] [Indexed: 12/15/2022]
Abstract
The recent, rapid increase in bacterial antimicrobial resistance has become a major public health concern. One approach to generate new classes of antibacterials is targeting virulence rather than the viability of bacteria. Proteins of the Dsb system, which play a key role in the virulence of many pathogenic microorganisms, represent potential new drug targets. The first part of the article presents current knowledge of how the Dsb system impacts function of various protein secretion systems that influence the virulence of many pathogenic bacteria. Next, the review describes methods used to study the structure, biochemistry, and microbiology of the Dsb proteins and shows how these experiments broaden our knowledge about their function. The lessons gained from basic research have led to a specific search for inhibitors blocking the Dsb networks.
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103
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Comprehensive Spatial Analysis of the Borrelia burgdorferi Lipoproteome Reveals a Compartmentalization Bias toward the Bacterial Surface. J Bacteriol 2017; 199:JB.00658-16. [PMID: 28069820 DOI: 10.1128/jb.00658-16] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 01/03/2017] [Indexed: 12/13/2022] Open
Abstract
The Lyme disease spirochete Borrelia burgdorferi is unique among bacteria in its large number of lipoproteins that are encoded by a small, exceptionally fragmented, and predominantly linear genome. Peripherally anchored in either the inner or outer membrane and facing either the periplasm or the external environment, these lipoproteins assume varied roles. A prominent subset of lipoproteins functioning as the apparent linchpins of the enzootic tick-vertebrate infection cycle have been explored as vaccine targets. Yet, most of the B. burgdorferi lipoproteome has remained uncharacterized. Here, we comprehensively and conclusively localize the B. burgdorferi lipoproteome by applying established protein localization assays to a newly generated epitope-tagged lipoprotein expression library and by validating the obtained individual protein localization results using a sensitive global mass spectrometry approach. The derived consensus localization data indicate that 86 of the 125 analyzed lipoproteins encoded by B. burgdorferi are secreted to the bacterial surface. Thirty-one of the remaining 39 periplasmic lipoproteins are retained in the inner membrane, with only 8 lipoproteins being anchored in the periplasmic leaflet of the outer membrane. The localization of 10 lipoproteins was further defined or revised, and 52 surface and 23 periplasmic lipoproteins were newly localized. Cross-referencing prior studies revealed that the borrelial surface lipoproteome contributing to the host-pathogen interface is encoded predominantly by plasmids. Conversely, periplasmic lipoproteins are encoded mainly by chromosomal loci. These studies close a gap in our understanding of the functional lipoproteome of an important human pathogen and set the stage for more in-depth studies of thus-far-neglected spirochetal lipoproteins.IMPORTANCE The small and exceptionally fragmented genome of the Lyme disease spirochete Borrelia burgdorferi encodes over 120 lipoproteins. Studies in the field have predominantly focused on a relatively small number of surface lipoproteins that play important roles in the transmission and pathogenesis of this global human pathogen. Yet, a comprehensive spatial assessment of the entire borrelial lipoproteome has been missing. The current study newly identifies 52 surface and 23 periplasmic lipoproteins. Overall, two-thirds of the B. burgdorferi lipoproteins localize to the surface, while outer membrane lipoproteins facing the periplasm are rare. This analysis underscores the dominant contribution of lipoproteins to the spirochete's rather complex and adaptable host-pathogen interface, and it encourages further functional exploration of its lipoproteome.
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104
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Ieva R. Interfering with outer membrane biogenesis to fight Gram-negative bacterial pathogens. Virulence 2017; 8:1049-1052. [PMID: 28277902 DOI: 10.1080/21505594.2017.1296617] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Affiliation(s)
- Raffaele Ieva
- a Laboratoire de Microbiologie et de Génétique Moléculaires (LMGM) , Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS , Toulouse , France
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105
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A tool named Iris for versatile high-throughput phenotyping in microorganisms. Nat Microbiol 2017; 2:17014. [PMID: 28211844 PMCID: PMC5464397 DOI: 10.1038/nmicrobiol.2017.14] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Accepted: 01/10/2017] [Indexed: 12/14/2022]
Abstract
Advances in our ability to systematically introduce and track controlled genetic variance in microbes have fueled high-throughput reverse genetics approaches in the past decade. When coupled to quantitative readouts, such approaches are extremely powerful at elucidating gene function and providing insights into the underlying pathways and the overall cellular network organization. Yet, until now all efforts for quantifying microbial macroscopic phenotypes have been restricted to monitoring growth in a small number of model microbes. We developed an image analysis software named Iris, which allows for systematic exploration of a number of orthogonal-to-growth processes, including biofilm formation, colony morphogenesis, envelope biogenesis, sporulation and reporter activity. In addition, Iris provides more sensitive growth measurements than current available software, and is compatible with a variety of different microbes, as well as with endpoint or kinetic data. We used Iris to reanalyze existing chemical genomics data in Escherichia coli and to perform proof-of-principle screens on colony biofilm formation and morphogenesis of different bacterial species and the pathogenic fungus, Candida albicans. Thereby we recapitulated existing knowledge but also identified a plethora of additional genes and pathways involved in both processes.
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106
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Narita SI, Tokuda H. Bacterial lipoproteins; biogenesis, sorting and quality control. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1862:1414-1423. [PMID: 27871940 DOI: 10.1016/j.bbalip.2016.11.009] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Revised: 11/11/2016] [Accepted: 11/14/2016] [Indexed: 12/20/2022]
Abstract
Bacterial lipoproteins are a subset of membrane proteins localized on either leaflet of the lipid bilayer. These proteins are anchored to membranes through their N-terminal lipid moiety attached to a conserved Cys. Since the protein moiety of most lipoproteins is hydrophilic, they are expected to play various roles in a hydrophilic environment outside the cytoplasmic membrane. Gram-negative bacteria such as Escherichia coli possess an outer membrane, to which most lipoproteins are sorted. The Lol pathway plays a central role in the sorting of lipoproteins to the outer membrane after lipoprotein precursors are processed to mature forms in the cytoplasmic membrane. Most lipoproteins are anchored to the inner leaflet of the outer membrane with their protein moiety in the periplasm. However, recent studies indicated that some lipoproteins further undergo topology change in the outer membrane, and play critical roles in the biogenesis and quality control of the outer membrane. This article is part of a Special Issue entitled: Bacterial Lipids edited by Russell E. Bishop.
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Affiliation(s)
| | - Hajime Tokuda
- University of Morioka, Takizawa, Iwate 020-0694, Japan.
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107
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Grabowicz M, Silhavy TJ. Envelope Stress Responses: An Interconnected Safety Net. Trends Biochem Sci 2016; 42:232-242. [PMID: 27839654 DOI: 10.1016/j.tibs.2016.10.002] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 10/12/2016] [Accepted: 10/17/2016] [Indexed: 12/14/2022]
Abstract
The Escherichia coli cell envelope is a protective barrier at the frontline of interaction with the environment. Fidelity of envelope biogenesis must be monitored to establish and maintain a contiguous barrier. Indeed, the envelope must also be repaired and modified in response to environmental assaults. Envelope stress responses (ESRs) sense envelope damage or defects and alter the transcriptome to mitigate stress. Here, we review recent insights into the stress-sensing mechanisms of the σE and Cpx systems and the interaction of these ESRs. Small RNAs (sRNAs) are increasingly prominent regulators of the transcriptional response to stress. These fast-acting regulators also provide avenues for inter-ESR regulation that could be important when cells face multiple contemporaneous stresses, as is the case during infection.
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Affiliation(s)
- Marcin Grabowicz
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Thomas J Silhavy
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA.
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108
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Filippova EV, Wawrzak Z, Ruan J, Pshenychnyi S, Schultz RM, Wolfe AJ, Anderson WF. Crystal structure of nonphosphorylated receiver domain of the stress response regulator RcsB from Escherichia coli. Protein Sci 2016; 25:2216-2224. [PMID: 27670836 DOI: 10.1002/pro.3050] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 09/23/2016] [Accepted: 09/23/2016] [Indexed: 11/12/2022]
Abstract
RcsB, the transcription-associated response regulator of the Rcs phosphorelay two-component signal transduction system, activates cell stress responses associated with desiccation, cell wall biosynthesis, cell division, virulence, biofilm formation, and antibiotic resistance in enteric bacterial pathogens. RcsB belongs to the FixJ/NarL family of transcriptional regulators, which are characterized by a highly conserved C-terminal DNA-binding domain. The N-terminal domain of RcsB belongs to the family of two-component receiver domains. This receiver domain contains the phosphoacceptor site and participates in RcsB dimer formation; it also contributes to dimer formation with other transcription factor partners. Here, we describe the crystal structure of the Escherichia coli RcsB receiver domain in its nonphosphorylated state. The structure reveals important molecular details of phosphorylation-independent dimerization of RcsB and has implication for the formation of heterodimers.
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Affiliation(s)
- Ekaterina V Filippova
- Department of Biochemistry and Molecular Genetics, Center for Structural Genomics of Infectious Diseases, Northwestern University Feinberg School of Medicine, Chicago, Illinois, 60611
| | - Zdzislaw Wawrzak
- Life Science Collaborative Access Team, Synchrotron Research Center, Northwestern University, Argonne, Illinois, 60439
| | - Jiapeng Ruan
- Yale University School of Medicine, Department of Digestive Diseases, New Haven, CT 06510
| | - Sergii Pshenychnyi
- Recombinant Protein Production Core, Northwestern University, Chemistry of Life Processes Institute, Evanston, Illinois 60208
| | - Richard M Schultz
- Department of Microbiology and Immunology, Loyola University Chicago, Health Sciences Division, Stritch School of Medicine, Maywood, Illinois, 60153
| | - Alan J Wolfe
- Department of Microbiology and Immunology, Loyola University Chicago, Health Sciences Division, Stritch School of Medicine, Maywood, Illinois, 60153
| | - Wayne F Anderson
- Department of Biochemistry and Molecular Genetics, Center for Structural Genomics of Infectious Diseases, Northwestern University Feinberg School of Medicine, Chicago, Illinois, 60611
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109
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Sperandeo P, Martorana AM, Polissi A. Lipopolysaccharide biogenesis and transport at the outer membrane of Gram-negative bacteria. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1862:1451-1460. [PMID: 27760389 DOI: 10.1016/j.bbalip.2016.10.006] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 10/11/2016] [Accepted: 10/13/2016] [Indexed: 01/10/2023]
Abstract
The outer membrane (OM) of Gram-negative bacteria is an asymmetric lipid bilayer containing a unique glycolipid, lipopolysaccharide (LPS) in its outer leaflet. LPS molecules confer to the OM peculiar permeability barrier properties enabling Gram-negative bacteria to exclude many toxic compounds, including clinically useful antibiotics, and to survive harsh environments. Transport of LPS poses several problems to the cells due to the amphipatic nature of this molecule. In this review we summarize the current knowledge on the LPS transport machinery, discuss the challenges associated with this process and present the solutions that bacterial cells have evolved to address the problem of LPS transport and assembly at the cell surface. Finally, we discuss how knowledge on LPS biogenesis can be translated for the development of novel antimicrobial therapies. This article is part of a Special Issue entitled: Bacterial Lipids edited by Russell E. Bishop.
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Affiliation(s)
- Paola Sperandeo
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milan, Italy.
| | - Alessandra M Martorana
- Dipartimento di Biotecnologie e Bioscienze, Università degli Studi di Milano-Bicocca, Milan, Italy
| | - Alessandra Polissi
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milan, Italy.
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110
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Szewczyk J, Collet JF. The Journey of Lipoproteins Through the Cell: One Birthplace, Multiple Destinations. Adv Microb Physiol 2016; 69:1-50. [PMID: 27720009 DOI: 10.1016/bs.ampbs.2016.07.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Bacterial lipoproteins are a very diverse group of proteins characterized by the presence of an N-terminal lipid moiety that serves as a membrane anchor. Lipoproteins have a wide variety of crucial functions, ranging from envelope biogenesis to stress response. In Gram-negative bacteria, lipoproteins can be targeted to various destinations in the cell, including the periplasmic side of the cytoplasmic or outer membrane, the cell surface or the external milieu. The sorting mechanisms have been studied in detail in Escherichia coli, but exceptions to the rules established in this model bacterium exist in other bacteria. In this chapter, we will present the current knowledge on lipoprotein sorting in the cell. Our particular focus will be on the surface-exposed lipoproteins that appear to be much more common than previously assumed. We will discuss the different targeting strategies, provide numerous examples of surface-exposed lipoproteins and discuss the techniques used to assess their surface exposure.
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Affiliation(s)
- J Szewczyk
- WELBIO, Brussels, Belgium; de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - J-F Collet
- WELBIO, Brussels, Belgium; de Duve Institute, Université catholique de Louvain, Brussels, Belgium.
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111
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Ren G, Ke N, Berkmen M. Use of the SHuffle Strains in Production of Proteins. ACTA ACUST UNITED AC 2016; 85:5.26.1-5.26.21. [PMID: 27479507 DOI: 10.1002/cpps.11] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Escherichia coli continues to be a popular expression host for the production of proteins, yet successful recombinant expression of active proteins to high yields remains a trial and error process. This is mainly due to decoupling of the folding factors of a protein from its native host, when expressed recombinantly in E. coli. Failure to fold could be due to many reasons but is often due to lack of post-translational modifications that are absent in E. coli. One such post-translational modification is the formation of disulfide bonds, a common feature of secreted proteins. The genetically engineered SHuffle cells offer an expression solution to proteins that require disulfide bonds for their folding and activity. The purpose of this protocol unit is to familiarize the researcher with the biology of SHuffle cells and guide the experimental design in order to optimize and increase the chances of successful expression of their desired protein of choice. Example of the expression and purification of a model disulfide-bonded protein DsbC is described in detail. © 2016 by John Wiley & Sons, Inc.
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Affiliation(s)
| | - Na Ke
- New England Biolabs, Ipswich, Massachusetts
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112
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Bocian-Ostrzycka KM, Grzeszczuk MJ, Banaś AM, Jastrząb K, Pisarczyk K, Kolarzyk A, Łasica AM, Collet JF, Jagusztyn-Krynicka EK. Engineering of Helicobacter pylori Dimeric Oxidoreductase DsbK (HP0231). Front Microbiol 2016; 7:1158. [PMID: 27507968 PMCID: PMC4960241 DOI: 10.3389/fmicb.2016.01158] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 07/12/2016] [Indexed: 12/16/2022] Open
Abstract
The formation of disulfide bonds that are catalyzed by proteins of the Dsb (disulfide bond) family is crucial for the correct folding of many extracytoplasmic proteins. Thus, this formation plays an essential, pivotal role in the assembly of many virulence factors. The Helicobacter pylori disulfide bond-forming system is uncomplicated compared to the best-characterized Escherichia coli Dsb pathways. It possesses only two extracytoplasmic Dsb proteins named HP0377 and HP0231. As previously shown, HP0377 is a reductase involved in the process of cytochrome c maturation. Additionally, it also possesses disulfide isomerase activity. HP0231 was the first periplasmic dimeric oxidoreductase involved in disulfide generation to be described. Although HP0231 function is critical for oxidative protein folding, its structure resembles that of dimeric EcDsbG, which does not confer this activity. However, the HP0231 catalytic motifs (CXXC and the so-called cis-Pro loop) are identical to that of monomeric EcDsbA. To understand the functioning of HP0231, we decided to study the relations between its sequence, structure and activity through an extensive analysis of various HP0231 point mutants, using in vivo and in vitro strategies. Our work shows the crucial role of the cis-Pro loop, as changing valine to threonine in this motif completely abolishes the protein function in vivo. Functioning of HP0231 is conditioned by the combination of CXXC and the cis-Pro loop, as replacing the HP0231 CXXC motif by the motif from EcDsbG or EcDsbC results in bifunctional protein, at least in E. coli. We also showed that the dimerization domain of HP0231 ensures contact with its substrates. Moreover, the activity of this oxidase is independent on the structure of the catalytic domain. Finally, we showed that HP0231 chaperone activity is independent of its redox function.
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Affiliation(s)
- Katarzyna M Bocian-Ostrzycka
- Department of Bacterial Genetics, Faculty of Biology, Institute of Microbiology, University of Warsaw Warsaw, Poland
| | - Magdalena J Grzeszczuk
- Department of Bacterial Genetics, Faculty of Biology, Institute of Microbiology, University of Warsaw Warsaw, Poland
| | - Anna M Banaś
- Department of Bacterial Genetics, Faculty of Biology, Institute of Microbiology, University of Warsaw Warsaw, Poland
| | - Katarzyna Jastrząb
- Department of Bacterial Genetics, Faculty of Biology, Institute of Microbiology, University of Warsaw Warsaw, Poland
| | - Karolina Pisarczyk
- Department of Bacterial Genetics, Faculty of Biology, Institute of Microbiology, University of Warsaw Warsaw, Poland
| | - Anna Kolarzyk
- Department of Bacterial Genetics, Faculty of Biology, Institute of Microbiology, University of Warsaw Warsaw, Poland
| | - Anna M Łasica
- Department of Bacterial Genetics, Faculty of Biology, Institute of Microbiology, University of Warsaw Warsaw, Poland
| | - Jean-François Collet
- Walloon Excellence in Life Sciences and BiotechnologyBrussels, Belgium; de Duve Institute, Université Catholique de LouvainBrussels, Belgium
| | - Elżbieta K Jagusztyn-Krynicka
- Department of Bacterial Genetics, Faculty of Biology, Institute of Microbiology, University of Warsaw Warsaw, Poland
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113
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De Geyter J, Tsirigotaki A, Orfanoudaki G, Zorzini V, Economou A, Karamanou S. Protein folding in the cell envelope of Escherichia coli. Nat Microbiol 2016; 1:16107. [PMID: 27573113 DOI: 10.1038/nmicrobiol.2016.107] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 06/02/2016] [Indexed: 11/09/2022]
Abstract
While the entire proteome is synthesized on cytoplasmic ribosomes, almost half associates with, localizes in or crosses the bacterial cell envelope. In Escherichia coli a variety of mechanisms are important for taking these polypeptides into or across the plasma membrane, maintaining them in soluble form, trafficking them to their correct cell envelope locations and then folding them into the right structures. The fidelity of these processes must be maintained under various environmental conditions including during stress; if this fails, proteases are called in to degrade mislocalized or aggregated proteins. Various soluble, diffusible chaperones (acting as holdases, foldases or pilotins) and folding catalysts are also utilized to restore proteostasis. These responses can be general, dealing with multiple polypeptides, with functional overlaps and operating within redundant networks. Other chaperones are specialized factors, dealing only with a few exported proteins. Several complex machineries have evolved to deal with binding to, integration in and crossing of the outer membrane. This complex protein network is responsible for fundamental cellular processes such as cell wall biogenesis; cell division; the export, uptake and degradation of molecules; and resistance against exogenous toxic factors. The underlying processes, contributing to our fundamental understanding of proteostasis, are a treasure trove for the development of novel antibiotics, biopharmaceuticals and vaccines.
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Affiliation(s)
- Jozefien De Geyter
- KU Leuven-University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, B-3000 Leuven, Belgium
| | - Alexandra Tsirigotaki
- KU Leuven-University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, B-3000 Leuven, Belgium
| | - Georgia Orfanoudaki
- Institute of Molecular Biology and Biotechnology, FORTH and Department of Biology, University of Crete, PO Box 1385, GR-711 10 Iraklio, Crete, Greece
| | - Valentina Zorzini
- KU Leuven-University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, B-3000 Leuven, Belgium
| | - Anastassios Economou
- KU Leuven-University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, B-3000 Leuven, Belgium.,Institute of Molecular Biology and Biotechnology, FORTH and Department of Biology, University of Crete, PO Box 1385, GR-711 10 Iraklio, Crete, Greece
| | - Spyridoula Karamanou
- KU Leuven-University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Molecular Bacteriology, B-3000 Leuven, Belgium
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114
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Abstract
The assembly of β-barrel proteins into membranes is mediated by an evolutionarily conserved machine. This process is poorly understood because no stable partially folded barrel substrates have been characterized. Here, we slowed the folding of the Escherichia coli β-barrel protein, LptD, with its lipoprotein plug, LptE. We identified a late-stage intermediate in which LptD is folded around LptE, and both components interact with the two essential β-barrel assembly machine (Bam) components, BamA and BamD. We propose a model in which BamA and BamD act in concert to catalyze folding, with the final step in the process involving closure of the ends of the barrel with release from the Bam components. Because BamD and LptE are both soluble proteins, the simplest model consistent with these findings is that barrel folding by the Bam complex begins in the periplasm at the membrane interface.
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115
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Konovalova A, Silhavy TJ. Outer membrane lipoprotein biogenesis: Lol is not the end. Philos Trans R Soc Lond B Biol Sci 2016; 370:rstb.2015.0030. [PMID: 26370942 DOI: 10.1098/rstb.2015.0030] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Bacterial lipoproteins are lipid-anchored proteins that contain acyl groups covalently attached to the N-terminal cysteine residue of the mature protein. Lipoproteins are synthesized in precursor form with an N-terminal signal sequence (SS) that targets translocation across the cytoplasmic or inner membrane (IM). Lipid modification and SS processing take place at the periplasmic face of the IM. Outer membrane (OM) lipoproteins take the localization of lipoproteins (Lol) export pathway, which ends with the insertion of the N-terminal lipid moiety into the inner leaflet of the OM. For many lipoproteins, the biogenesis pathway ends here. We provide examples of lipoproteins that adopt complex topologies in the OM that include transmembrane and surface-exposed domains. Biogenesis of such lipoproteins requires additional steps beyond the Lol pathway. In at least one case, lipoprotein sequences reach the cell surface by being threaded through the lumen of a beta-barrel protein in an assembly reaction that requires the heteropentomeric Bam complex. The inability to predict surface exposure reinforces the importance of experimental verification of lipoprotein topology and we will discuss some of the methods used to study OM protein topology.
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Affiliation(s)
- Anna Konovalova
- Department of Molecular Biology, Lewis Thomas Laboratory, Princeton University, Washington Road, Princeton, NJ 08544, USA
| | - Thomas J Silhavy
- Department of Molecular Biology, Lewis Thomas Laboratory, Princeton University, Washington Road, Princeton, NJ 08544, USA
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116
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Konovalova A, Mitchell AM, Silhavy TJ. A lipoprotein/β-barrel complex monitors lipopolysaccharide integrity transducing information across the outer membrane. eLife 2016; 5. [PMID: 27282389 PMCID: PMC4942254 DOI: 10.7554/elife.15276] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 06/07/2016] [Indexed: 11/13/2022] Open
Abstract
Lipoprotein RcsF is the OM component of the Rcs envelope stress response. RcsF exists in complexes with β-barrel proteins (OMPs) allowing it to adopt a transmembrane orientation with a lipidated N-terminal domain on the cell surface and a periplasmic C-terminal domain. Here we report that mutations that remove BamE or alter a residue in the RcsF trans-lumen domain specifically prevent assembly of the interlocked complexes without inactivating either RcsF or the OMP. Using these mutations we demonstrate that these RcsF/OMP complexes are required for sensing OM outer leaflet stress. Using mutations that alter the positively charged surface-exposed domain, we show that RcsF monitors lateral interactions between lipopolysaccharide (LPS) molecules. When these interactions are disrupted by cationic antimicrobial peptides, or by the loss of negatively charged phosphate groups on the LPS molecule, this information is transduced to the RcsF C-terminal signaling domain located in the periplasm to activate the stress response. DOI:http://dx.doi.org/10.7554/eLife.15276.001 Many disease-causing bacteria have an outer membrane that surrounds and protects the cell, while many hosts of these bacteria produce molecules called antimicrobial peptides that disrupt this outer membrane. In response to this attack, bacteria have evolved a defense system to reinforce their membrane when antimicrobial peptides are present. However, it was not clear how the bacteria sensed these peptides. One clue came from a recent discovery that the bacterial protein required for sensing the peptides is threaded through a barrel-shaped protein to expose a section of it on the bacterial cell’s surface. Now, Konovalova et al. have tested if this surface-exposed domain directly detects damage to the outer membrane caused by the antimicrobial peptides. The investigation revealed several mutants of Escherichia coli that still make the sensor protein but are unable to thread it through the barrel-shaped protein and place a portion on the cell surface. Konovalova et al. showed that these mutants are essentially “blind” to the presence of antimicrobial peptides, and thus prove that it is the surface-exposed domain that works as the sensor. Antimicrobial peptides bind to a major component of the outer membrane and disrupt its normal interactions. Further experiments showed that positively charged sites in surface-exposed domain of the sensor are required to detect these changes and transmit this information inside the cell. Future studies are now needed to understand how the sensor is assembled inside the barrel-shaped protein, and how the danger signal is sent across the membranes that envelope bacterial cells to activate the defense system inside the cell. DOI:http://dx.doi.org/10.7554/eLife.15276.002
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Affiliation(s)
- Anna Konovalova
- Department of Molecular Biology, Princeton University, Lewis Thomas Laboratory, Princeton, United States
| | - Angela M Mitchell
- Department of Molecular Biology, Princeton University, Lewis Thomas Laboratory, Princeton, United States
| | - Thomas J Silhavy
- Department of Molecular Biology, Princeton University, Lewis Thomas Laboratory, Princeton, United States
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117
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Villacorte M, Delmarcelle AS, Lernoux M, Bouquet M, Lemoine P, Bolsée J, Umans L, de Sousa Lopes SC, Van Der Smissen P, Sasaki T, Bommer G, Henriet P, Refetoff S, Lemaigre FP, Zwijsen A, Courtoy PJ, Pierreux CE. Thyroid follicle development requires Smad1/5- and endothelial cell-dependent basement membrane assembly. Development 2016; 143:1958-70. [PMID: 27068110 DOI: 10.1242/dev.134171] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 04/01/2016] [Indexed: 12/12/2022]
Abstract
Thyroid follicles, the functional units of the thyroid gland, are delineated by a monolayer of thyrocytes resting on a continuous basement membrane. The developmental mechanisms of folliculogenesis, whereby follicles are formed by the reorganization of a non-structured mass of non-polarized epithelial cells, are largely unknown. Here we show that assembly of the epithelial basement membrane is crucial for folliculogenesis and is controlled by endothelial cell invasion and by BMP-Smad signaling in thyrocytes. Thyroid-specific Smad1 and Smad5 double-knockout (Smad1/5(dKO)) mice displayed growth retardation, hypothyroidism and defective follicular architecture. In Smad1/5(dKO) embryonic thyroids, epithelial cells remained associated in large clusters and formed small follicles. Although similar follicular defects are found in Vegfa knockout (Vegfa(KO)) thyroids, Smad1/5(dKO) thyroids had normal endothelial cell density yet impaired endothelial differentiation. Interestingly, both Vegfa(KO) and Smad1/5(dKO) thyroids displayed impaired basement membrane assembly. Furthermore, conditioned medium (CM) from embryonic endothelial progenitor cells (eEPCs) rescued the folliculogenesis defects of both Smad1/5(dKO) and Vegfa(KO) thyroids. Laminin α1, β1 and γ1, abundantly released by eEPCs into CM, were crucial for folliculogenesis. Thus, epithelial Smad signaling and endothelial cell invasion promote folliculogenesis via assembly of the basement membrane.
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Affiliation(s)
- Mylah Villacorte
- de Duve Institute and Université Catholique de Louvain, 1200 Brussels, Belgium
| | | | - Manon Lernoux
- de Duve Institute and Université Catholique de Louvain, 1200 Brussels, Belgium
| | - Mahé Bouquet
- de Duve Institute and Université Catholique de Louvain, 1200 Brussels, Belgium
| | - Pascale Lemoine
- de Duve Institute and Université Catholique de Louvain, 1200 Brussels, Belgium
| | - Jennifer Bolsée
- de Duve Institute and Université Catholique de Louvain, 1200 Brussels, Belgium
| | - Lieve Umans
- VIB Center for the Biology of Disease, KU Leuven, 3000 Leuven, Belgium Laboratory of Molecular Biology (Celgen), Stem Cell Biology and Embryology, KU Leuven, 2333 Leuven, Belgium
| | | | | | - Takako Sasaki
- Department of Matrix Medicine, Faculty of Medicine, Oita University, 879-5593 Oita, Japan
| | - Guido Bommer
- de Duve Institute and Université Catholique de Louvain, 1200 Brussels, Belgium
| | - Patrick Henriet
- de Duve Institute and Université Catholique de Louvain, 1200 Brussels, Belgium
| | - Samuel Refetoff
- Department of Medicine, Pediatrics and Genetics, The University of Chicago, Chicago, IL 60637, USA
| | - Frédéric P Lemaigre
- de Duve Institute and Université Catholique de Louvain, 1200 Brussels, Belgium
| | - An Zwijsen
- VIB Center for the Biology of Disease, KU Leuven, 3000 Leuven, Belgium Department of Human Genetics, KU Leuven, Leuven, Belgium
| | - Pierre J Courtoy
- de Duve Institute and Université Catholique de Louvain, 1200 Brussels, Belgium
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118
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Hooda Y, Lai CCL, Judd A, Buckwalter CM, Shin HE, Gray-Owen SD, Moraes TF. Slam is an outer membrane protein that is required for the surface display of lipidated virulence factors in Neisseria. Nat Microbiol 2016; 1:16009. [DOI: 10.1038/nmicrobiol.2016.9] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Accepted: 01/19/2016] [Indexed: 11/09/2022]
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119
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Fine-Tuning of the Cpx Envelope Stress Response Is Required for Cell Wall Homeostasis in Escherichia coli. mBio 2016; 7:e00047-16. [PMID: 26908573 PMCID: PMC4791840 DOI: 10.1128/mbio.00047-16] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The envelope of Gram-negative bacteria is an essential compartment that constitutes a protective and permeability barrier between the cell and its environment. The envelope also hosts the cell wall, a mesh-like structure made of peptidoglycan (PG) that determines cell shape and provides osmotic protection. Since the PG must grow and divide in a cell-cycle-synchronized manner, its synthesis and remodeling are tightly regulated. Here, we discovered that PG homeostasis is intimately linked to the levels of activation of the Cpx system, an envelope stress response system traditionally viewed as being involved in protein quality control in the envelope. We first show that Cpx is activated when PG integrity is challenged and that this activation provides protection to cells exposed to antibiotics inhibiting PG synthesis. By rerouting the outer membrane lipoprotein NlpE, a known Cpx activator, to a different envelope subcompartment, we managed to manipulate Cpx activation levels. We found that Cpx overactivation leads to aberrant cellular morphologies, to an increased sensitivity to β-lactams, and to dramatic division and growth defects, consistent with a loss of PG homeostasis. Remarkably, these phenotypes were largely abrogated by the deletion of ldtD, a Cpx-induced gene involved in noncanonical PG cross-linkage, suggesting that this transpeptidase is an important link between PG homeostasis and the Cpx system. Altogether our data show that fine-tuning of an envelope quality control system constitutes an important layer of regulation of the highly organized cell wall structure. The envelope of Gram-negative bacteria is essential for viability. First, it includes the cell wall, a continuous polymer of peptidoglycan (PG) that determines cell morphology and protects against osmotic stress. Moreover, the envelope constitutes a protective barrier between the cell interior and the environment. Therefore, mechanisms called envelope stress response systems (ESRS) exist to monitor and defend envelope integrity against harmful conditions. Cpx is a major ESRS that detects and manages the accumulation of misfolded proteins in the envelope of Escherichia coli. We found that this protein quality control system also plays a fundamental role in the regulation of PG assembly. Strikingly, the level of Cpx response is critical, as an excessive activation leads to phenotypes associated with a loss of cell wall integrity. Thus, by contributing to PG homeostasis, the Cpx system lies at the crossroads between key processes of bacterial life, including cell shape, growth, division, and antibiotic resistance.
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120
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Wilson MM, Bernstein HD. Surface-Exposed Lipoproteins: An Emerging Secretion Phenomenon in Gram-Negative Bacteria. Trends Microbiol 2015; 24:198-208. [PMID: 26711681 DOI: 10.1016/j.tim.2015.11.006] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 11/17/2015] [Accepted: 11/23/2015] [Indexed: 01/07/2023]
Abstract
Bacterial lipoproteins are hydrophilic proteins that are anchored to a cell membrane by N-terminally linked fatty acids. It is widely believed that nearly all lipoproteins produced by Gram-negative bacteria are either retained in the inner membrane (IM) or transferred to the inner leaflet of the outer membrane (OM). Lipoproteins that are exposed on the cell surface have also been reported but are generally considered to be rare. Results from a variety of recent studies, however, now suggest that the prevalence of surface-exposed lipoproteins has been underestimated. In this review we describe the evidence that the surface exposure of lipoproteins in Gram-negative bacteria is a widespread phenomenon and discuss possible mechanisms by which these proteins might be transported across the OM.
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Affiliation(s)
- Marlena M Wilson
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Harris D Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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121
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Pannen D, Fabisch M, Gausling L, Schnetz K. Interaction of the RcsB Response Regulator with Auxiliary Transcription Regulators in Escherichia coli. J Biol Chem 2015; 291:2357-70. [PMID: 26635367 DOI: 10.1074/jbc.m115.696815] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Indexed: 11/06/2022] Open
Abstract
The Rcs phosphorelay is a two-component signal transduction system that is induced by cell envelope stress. RcsB, the response regulator of this signaling system, is a pleiotropic transcription regulator, which is involved in the control of various stress responses, cell division, motility, and biofilm formation. RcsB regulates transcription either as a homodimer or together with auxiliary regulators, such as RcsA, BglJ, and GadE in Escherichia coli. In this study, we show that RcsB in addition forms heterodimers with MatA (also known as EcpR) and with DctR. Our data suggest that the MatA-dependent transcription regulation is mediated by the MatA-RcsB heterodimer and is independent of RcsB phosphorylation. Furthermore, we analyzed the relevance of amino acid residues of the active quintet of conserved residues, and of surface-exposed residues for activity of RcsB. The data suggest that the activity of the phosphorylation-dependent dimers, such as RcsA-RcsB and RcsB-RcsB, is affected by mutation of residues in the vicinity of the phosphorylation site, suggesting that a phosphorylation-induced structural change modulates their activity. In contrast, the phosphorylation-independent heterodimers BglJ-RcsB and MatA-RcsB are affected by only very few mutations. Heterodimerization of RcsB with various auxiliary regulators and their differential dependence on phosphorylation add an additional level of control to the Rcs system that is operating at the output level.
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Affiliation(s)
- Derk Pannen
- From the Institute for Genetics, University of Cologne, Zülpicher Strasse 47a, 50674 Cologne, Germany
| | - Maria Fabisch
- From the Institute for Genetics, University of Cologne, Zülpicher Strasse 47a, 50674 Cologne, Germany
| | - Lisa Gausling
- From the Institute for Genetics, University of Cologne, Zülpicher Strasse 47a, 50674 Cologne, Germany
| | - Karin Schnetz
- From the Institute for Genetics, University of Cologne, Zülpicher Strasse 47a, 50674 Cologne, Germany
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122
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Kleanthous C, Rassam P, Baumann CG. Protein-protein interactions and the spatiotemporal dynamics of bacterial outer membrane proteins. Curr Opin Struct Biol 2015; 35:109-15. [PMID: 26629934 PMCID: PMC4684144 DOI: 10.1016/j.sbi.2015.10.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Revised: 10/26/2015] [Accepted: 10/30/2015] [Indexed: 01/14/2023]
Abstract
We discuss spatiotemporal patterning in the bacterial outer membrane. Promiscuous interactions between outer membrane proteins govern their behaviour. Turnover and biogenesis of outer membrane proteins linked to formation of clusters. Implications of spatiotemporal patterning for bacterial physiology discussed.
It has until recently been unclear whether outer membrane proteins (OMPs) of Gram-negative bacteria are organized or distributed randomly. Studies now suggest promiscuous protein–protein interactions (PPIs) between β-barrel OMPs in Escherichia coli govern their local and global dynamics, engender spatiotemporal patterning of the outer membrane into micro-domains and are the basis of β-barrel protein turnover. We contextualize these latest advances, speculate on areas of bacterial cell biology that might be influenced by the organization of OMPs into supramolecular assemblies, and highlight the new questions and controversies this revised view of the bacterial outer membrane raises.
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Affiliation(s)
- Colin Kleanthous
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
| | - Patrice Rassam
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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123
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Bacterial Networks in Cells and Communities. J Mol Biol 2015; 427:3785-92. [PMID: 26506266 DOI: 10.1016/j.jmb.2015.10.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 10/21/2015] [Accepted: 10/21/2015] [Indexed: 01/26/2023]
Abstract
Research on the bacterial regulatory networks is currently experiencing a true revival, driven by advances in methodology and by emergence of novel concepts. The biannual conference Bacterial Networks (BacNet15) held in May 2015, in Sant Feliu de Guíxols, Spain, covered progress in the studies of regulatory networks that control bacterial physiology, cell biology, stress responses, metabolism, collective behavior and evolution. It demonstrated how interdisciplinary approaches that combine molecular biology and biochemistry with the latest microscopy developments, whole cell (-omics) approaches and mathematical modeling can help understand design principles relevant in microbiology. It further showed how current biotechnology and medical microbiology could profit from our knowledge of and ability to engineer regulatory networks of bacteria.
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124
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Bocian-Ostrzycka KM, Łasica AM, Dunin-Horkawicz S, Grzeszczuk MJ, Drabik K, Dobosz AM, Godlewska R, Nowak E, Collet JF, Jagusztyn-Krynicka EK. Functional and evolutionary analyses of Helicobacter pylori HP0231 (DsbK) protein with strong oxidative and chaperone activity characterized by a highly diverged dimerization domain. Front Microbiol 2015; 6:1065. [PMID: 26500620 PMCID: PMC4597128 DOI: 10.3389/fmicb.2015.01065] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 09/16/2015] [Indexed: 12/15/2022] Open
Abstract
Helicobacter pylori does not encode the classical DsbA/DsbB oxidoreductases that are crucial for oxidative folding of extracytoplasmic proteins. Instead, this microorganism encodes an untypical two proteins playing a role in disulfide bond formation – periplasmic HP0231, which structure resembles that of EcDsbC/DsbG, and its redox partner, a membrane protein HpDsbI (HP0595) with a β-propeller structure. The aim of presented work was to assess relations between HP0231 structure and function. We showed that HP0231 is most closely related evolutionarily to the catalytic domain of DsbG, even though it possesses a catalytic motif typical for canonical DsbA proteins. Similarly, the highly diverged N-terminal dimerization domain is homologous to the dimerization domain of DsbG. To better understand the functioning of this atypical oxidoreductase, we examined its activity using in vivo and in vitro experiments. We found that HP0231 exhibits oxidizing and chaperone activities but no isomerizing activity, even though H. pylori does not contain a classical DsbC. We also show that HP0231 is not involved in the introduction of disulfide bonds into HcpC (Helicobactercysteine-rich protein C), a protein involved in the modulation of the H. pylori interaction with its host. Additionally, we also constructed a truncated version of HP0231 lacking the dimerization domain, denoted HP0231m, and showed that it acts in Escherichia coli cells in a DsbB-dependent manner. In contrast, HP0231m and classical monomeric EcDsbA (E. coli DsbA protein) were both unable to complement the lack of HP0231 in H. pylori cells, though they exist in oxidized forms. HP0231m is inactive in the insulin reduction assay and possesses high chaperone activity, in contrast to EcDsbA. In conclusion, HP0231 combines oxidative functions characteristic of DsbA proteins and chaperone activity characteristic of DsbC/DsbG, and it lacks isomerization activity.
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Affiliation(s)
- Katarzyna M Bocian-Ostrzycka
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw Warsaw, Poland
| | - Anna M Łasica
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology Warsaw, Poland
| | - Stanisław Dunin-Horkawicz
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology Warsaw, Poland
| | - Magdalena J Grzeszczuk
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw Warsaw, Poland
| | - Karolina Drabik
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw Warsaw, Poland
| | - Aneta M Dobosz
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw Warsaw, Poland
| | - Renata Godlewska
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw Warsaw, Poland
| | - Elżbieta Nowak
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology Warsaw, Poland
| | - Jean-Francois Collet
- de Duve Institute, Université catholique de Louvain (UCL)/Walloon Excellence in Life Sciences and Biotechnology Brussels, Belgium
| | - Elżbieta K Jagusztyn-Krynicka
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw Warsaw, Poland
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125
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Allen MD, Christie M, Jones P, Porebski BT, Roome B, Freund SMV, Buckle AM, Bycroft M, Christ D. Solution structure of a soluble fragment derived from a membrane protein by shotgun proteolysis. Protein Eng Des Sel 2015; 28:445-50. [PMID: 25877662 PMCID: PMC4661788 DOI: 10.1093/protein/gzv021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Revised: 02/16/2015] [Accepted: 03/09/2015] [Indexed: 11/14/2022] Open
Abstract
We have previously reported a phage display method for the identification of protein domains on a genome-wide scale (shotgun proteolysis). Here we present the solution structure of a fragment of the Escherichia coli membrane protein yrfF, as identified by shotgun proteolysis, and determined by NMR spectroscopy. Despite the absence of computational predictions, the fragment formed a well-defined beta-barrel structure, distantly falling within the OB-fold classification. Our results highlight the potential of high-throughput experimental approaches for the identification of protein domains for structural studies.
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Affiliation(s)
- Mark D Allen
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
| | - Mary Christie
- Department of Immunology, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, Sydney, NSW 2010, Australia Faculty of Medicine, St Vincent's Clinical School, The University of New South Wales, Darlinghurst, Sydney, NSW 2010, Australia
| | - Peter Jones
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
| | - Benjamin T Porebski
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Brendan Roome
- Department of Immunology, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, Sydney, NSW 2010, Australia Faculty of Medicine, St Vincent's Clinical School, The University of New South Wales, Darlinghurst, Sydney, NSW 2010, Australia
| | - Stefan M V Freund
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
| | - Ashley M Buckle
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Mark Bycroft
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
| | - Daniel Christ
- Department of Immunology, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, Sydney, NSW 2010, Australia Faculty of Medicine, St Vincent's Clinical School, The University of New South Wales, Darlinghurst, Sydney, NSW 2010, Australia
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126
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Chong ZS, Woo WF, Chng SS. Osmoporin OmpC forms a complex with MlaA to maintain outer membrane lipid asymmetry in Escherichia coli. Mol Microbiol 2015; 98:1133-46. [PMID: 26314242 DOI: 10.1111/mmi.13202] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/24/2015] [Indexed: 12/21/2022]
Abstract
Gram-negative bacteria can survive in harsh environments in part because the asymmetric outer membrane (OM) hinders the entry of toxic compounds. Lipid asymmetry is established by having phospholipids (PLs) confined to the inner leaflet of the membrane and lipopolysaccharides (LPS) to the outer leaflet. Perturbation of OM lipid asymmetry, characterized by PL accumulation in the outer leaflet, disrupts proper LPS packing and increases membrane permeability. The multi-component Mla system prevents PL accumulation in the outer leaflet of the OM via an unknown mechanism. Here, we demonstrate that in Escherichia coli, the Mla system maintains OM lipid asymmetry with the help of osmoporin OmpC. We show that the OM lipoprotein MlaA interacts specifically with OmpC and OmpF. This interaction is sufficient to localize MlaA lacking its lipid anchor to the OM. Removing OmpC, but not OmpF, causes accumulation of PLs in the outer leaflet of the OM in stationary phase, as was previously observed for MlaA. We establish that OmpC is an additional component of the Mla system; the OmpC-MlaA complex may function to remove PLs directly from the outer leaflet to maintain OM lipid asymmetry. Our work reveals a novel function for the general diffusion channel OmpC in lipid transport.
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Affiliation(s)
- Zhi-Soon Chong
- Department of Chemistry, National University of Singapore, Singapore, 117543
| | - Wei-Fen Woo
- Department of Chemistry, National University of Singapore, Singapore, 117543
| | - Shu-Sin Chng
- Department of Chemistry, National University of Singapore, Singapore, 117543.,Singapore Center on Environmental Life Sciences Engineering (SCELSE), National University of Singapore, Singapore, 117456
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127
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Harshey RM, Partridge JD. Shelter in a Swarm. J Mol Biol 2015; 427:3683-94. [PMID: 26277623 DOI: 10.1016/j.jmb.2015.07.025] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Revised: 07/29/2015] [Accepted: 07/31/2015] [Indexed: 01/04/2023]
Abstract
Flagella propel bacteria during both swimming and swarming, dispersing them widely. However, while swimming bacteria use chemotaxis to find nutrients and avoid toxic environments, swarming bacteria appear to suppress chemotaxis and to use the dynamics of their collective motion to continuously expand and acquire new territory, barrel through lethal chemicals in their path, carry along bacterial and fungal cargo that assists in exploration of new niches, and engage in group warfare for niche dominance. Here, we focus on two aspects of swarming, which, if understood, hold the promise of revealing new insights into microbial signaling and behavior, with ramifications beyond bacterial swarming. These are as follows: how bacteria sense they are on a surface and turn on programs that promote movement and how they override scarcity and adversity as dense packs.
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Affiliation(s)
- Rasika M Harshey
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA.
| | - Jonathan D Partridge
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA
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128
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Small RNA-based feedforward loop with AND-gate logic regulates extrachromosomal DNA transfer in Salmonella. Proc Natl Acad Sci U S A 2015; 112:E4772-81. [PMID: 26307765 DOI: 10.1073/pnas.1507825112] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Horizontal gene transfer via plasmid conjugation is a major driving force in microbial evolution but constitutes a complex process that requires synchronization with the physiological state of the host bacteria. Although several host transcription factors are known to regulate plasmid-borne transfer genes, RNA-based regulatory circuits for host-plasmid communication remain unknown. We describe a posttranscriptional mechanism whereby the Hfq-dependent small RNA, RprA, inhibits transfer of pSLT, the virulence plasmid of Salmonella enterica. RprA employs two separate seed-pairing domains to activate the mRNAs of both the sigma-factor σ(S) and the RicI protein, a previously uncharacterized membrane protein here shown to inhibit conjugation. Transcription of ricI requires σ(S) and, together, RprA and σ(S) orchestrate a coherent feedforward loop with AND-gate logic to tightly control the activation of RicI synthesis. RicI interacts with the conjugation apparatus protein TraV and limits plasmid transfer under membrane-damaging conditions. To our knowledge, this study reports the first small RNA-controlled feedforward loop relying on posttranscriptional activation of two independent targets and an unexpected role of the conserved RprA small RNA in controlling extrachromosomal DNA transfer.
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129
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YjjQ Represses Transcription of flhDC and Additional Loci in Escherichia coli. J Bacteriol 2015; 197:2713-20. [PMID: 26078445 DOI: 10.1128/jb.00263-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Accepted: 06/04/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The presumptive transcriptional regulator YjjQ has been identified as being virulence associated in avian pathogenic Escherichia coli (APEC). In this work, we characterize YjjQ as transcriptional repressor of the flhDC operon, encoding the master regulator of flagellar synthesis, and of additional loci. The latter include gfc (capsule 4 synthesis), ompC (outer membrane porin C), yfiRNB (regulated c-di-GMP synthesis), and loci of poorly defined function (ybhL and ymiA-yciX). We identify the YjjQ DNA-binding sites at the flhDC and gfc promoters and characterize a DNA-binding sequence motif present at all promoters found to be repressed by YjjQ. At the flhDC promoter, the YjjQ DNA-binding site overlaps the RcsA-RcsB DNA-binding site. RcsA-RcsB likewise represses the flhDC promoter, but the repression by YjjQ and that by RcsA-RcsB are independent of each other. These data suggest that YjjQ is an additional regulator involved in the complex control of flhDC at the level of transcription initiation. Furthermore, we show that YjjQ represses motility of the E. coli K-12 laboratory strain and of uropathogenic E. coli (UPEC) strains CFT073 and 536. Regulation of flhDC, yfiRNB, and additional loci by YjjQ may be features relevant for pathogenicity. IMPORTANCE Escherichia coli is a commensal and pathogenic bacterium causing intra- and extraintestinal infections in humans and farm animals. The pathogenicity of E. coli strains is determined by their particular genome content, which includes essential and associated virulence factors that control the cellular physiology in the host environment. However, the gene pools of commensal and pathogenic E. coli are not clearly differentiated, and the function of virulence-associated loci needs to be characterized. In this study, we characterize the function of yjjQ, encoding a transcription regulator that was identified as being virulence associated in avian pathogenic E. coli (APEC). We characterize YjjQ as transcriptional repressor of flagellar motility and of additional loci related to pathogenicity.
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130
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Bernstein HD. Looks can be deceiving: recent insights into the mechanism of protein secretion by the autotransporter pathway. Mol Microbiol 2015; 97:205-15. [PMID: 25881492 DOI: 10.1111/mmi.13031] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/15/2015] [Indexed: 12/14/2022]
Abstract
Autotransporters are a large superfamily of cell surface proteins produced by Gram-negative bacteria that consist of an N-terminal extracellular domain ('passenger domain') and a C-terminal β-barrel domain that resides in the outer membrane (OM). Although it was originally proposed that the passenger domain is translocated across the OM through a channel formed exclusively by the covalently linked β-barrel domain, this idea has been strongly challenged by a variety of observations. Recent experimental results have suggested a new model in which both the translocation of the passenger domain and the membrane integration of the β-barrel domain are facilitated by the Bam complex, a highly conserved heteroligomer that plays a general role in OM protein assembly. Other factors, including periplasmic chaperones and inner membrane proteins, have also recently been implicated in the biogenesis of at least some members of the autotransporter superfamily. New results have raised intriguing questions about the energetics of the secretion reaction and the relationship between the assembly of autotransporters and the assembly of other classes of OM proteins. Concomitantly, new mechanistic and structural insights have expanded the utility of the autotransporter pathway for the surface display of heterologous peptides and proteins of interest.
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Affiliation(s)
- Harris D Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA
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131
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Arts IS, Gennaris A, Collet JF. Reducing systems protecting the bacterial cell envelope from oxidative damage. FEBS Lett 2015; 589:1559-68. [DOI: 10.1016/j.febslet.2015.04.057] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 04/29/2015] [Indexed: 02/07/2023]
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