1
|
Guilvout I, Samsudin F, Huber RG, Bond PJ, Bardiaux B, Francetic O. Membrane platform protein PulF of the Klebsiella type II secretion system forms a trimeric ion channel essential for endopilus assembly and protein secretion. mBio 2024; 15:e0142323. [PMID: 38063437 PMCID: PMC10790770 DOI: 10.1128/mbio.01423-23] [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: 06/05/2023] [Accepted: 10/24/2023] [Indexed: 01/17/2024] Open
Abstract
IMPORTANCE Type IV pili and type II secretion systems are members of the widespread type IV filament (T4F) superfamily of nanomachines that assemble dynamic and versatile surface fibers in archaea and bacteria. The assembly and retraction of T4 filaments with diverse surface properties and functions require the plasma membrane platform proteins of the GspF/PilC superfamily. Generally considered dimeric, platform proteins are thought to function as passive transmitters of the mechanical energy generated by the ATPase motor, to somehow promote insertion of pilin subunits into the nascent pilus fibers. Here, we generate and experimentally validate structural predictions that support the trimeric state of a platform protein PulF from a type II secretion system. The PulF trimers form selective proton or sodium channels which might energize pilus assembly using the membrane potential. The conservation of the channel sequence and structural features implies a common mechanism for all T4F assembly systems. We propose a model of the oligomeric PulF-PulE ATPase complex that provides an essential framework to investigate and understand the pilus assembly mechanism.
Collapse
Affiliation(s)
- Ingrid Guilvout
- Institut Pasteur, Université Paris Cité, CNRS UMR 3528, Biochemistry of Macromolecular Interactions Unit, Paris, France
| | | | | | - Peter J. Bond
- Bioinformatics Institute (A-STAR), Singapore, Singapore
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Benjamin Bardiaux
- Institut Pasteur, Université Paris Cité, CNRS UMR 3528, Structural Bioinformatics Unit, Paris, France
- Institut Pasteur, Université Paris Cité, CNRS UMR 3528, Bacterial Transmembrane Systems Unit, Paris, France
| | - Olivera Francetic
- Institut Pasteur, Université Paris Cité, CNRS UMR 3528, Biochemistry of Macromolecular Interactions Unit, Paris, France
| |
Collapse
|
2
|
Krekhno Z, Woodward SE, Serapio-Palacios A, Peña-Díaz J, Moon KM, Foster LJ, Finlay BB. Citrobacter rodentium possesses a functional type II secretion system necessary for successful host infection. Gut Microbes 2024; 16:2308049. [PMID: 38299318 PMCID: PMC10841016 DOI: 10.1080/19490976.2024.2308049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 01/17/2024] [Indexed: 02/02/2024] Open
Abstract
Infectious diarrheal diseases are the third leading cause of mortality in young children, many of which are driven by Gram-negative bacterial pathogens. To establish successful host infections these pathogens employ a plethora of virulence factors necessary to compete with the resident microbiota, and evade and subvert the host defenses. The type II secretion system (T2SS) is one such conserved molecular machine that allows for the delivery of effector proteins into the extracellular milieu. To explore the role of the T2SS during natural host infection, we used Citrobacter rodentium, a murine enteric pathogen, as a model of human intestinal disease caused by pathogenic Escherichia coli such as Enteropathogenic and Enterohemorrhagic E. coli (EPEC and EHEC). In this study, we determined that the C. rodentium genome encodes one T2SS and 22 potential T2SS-secreted protein effectors, as predicted via sequence homology. We demonstrated that this system was functional in vitro, identifying a role in intestinal mucin degradation allowing for its utilization as a carbon source, and promoting C. rodentium attachment to a mucus-producing colon cell line. During host infection, loss of the T2SS or associated effectors led to a significant colonization defect and lack of systemic spread. In mice susceptible to lethal infection, T2SS-deficient C. rodentium was strongly attenuated, resulting in reduced morbidity and mortality in infected hosts. Together these data highlight the important role of the T2SS and its effector repertoire during C. rodentium pathogenesis, aiding in successful host mucosal colonization.
Collapse
Affiliation(s)
- Z Krekhno
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
| | - SE Woodward
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
| | - A Serapio-Palacios
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
| | - J Peña-Díaz
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
| | - KM Moon
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
| | - LJ Foster
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - BB Finlay
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| |
Collapse
|
3
|
Yang P, Qu C, Yuan M, Xi B, Jia X, Zhang B, Zhang L. Genetic Basis and Expression Pattern Indicate the Biocontrol Potential and Soil Adaption of Lysobacter capsici CK09. Microorganisms 2023; 11:1768. [PMID: 37512940 PMCID: PMC10384520 DOI: 10.3390/microorganisms11071768] [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: 06/06/2023] [Revised: 06/27/2023] [Accepted: 06/28/2023] [Indexed: 07/30/2023] Open
Abstract
Lysobacter species have attracted increasing attention in recent years due to their capacities to produce diverse secondary metabolites against phytopathogens. In this research, we analyzed the genomic and transcriptomic patterns of Lysobacter capsici CK09. Our data showed that L. capsici CK09 harbored various contact-independent biocontrol traits, such as fungal cell wall lytic enzymes and HSAF/WAP-8294A2 biosynthesis, as well as several contact-dependent machineries, including type 2/4/6 secretion systems. Additionally, a variety of hydrolytic enzymes, particularly extracellular enzymes, were found in the L. capsici CK09 genome and predicted to improve its adaption in soil. Furthermore, several systems, including type 4 pili, type 3 secretion system and polysaccharide biosynthesis, can provide a selective advantage to L. capsici CK09, enabling the species to live on the surface in soil. The expression of these genes was then confirmed via transcriptomic analysis, indicating the activities of these genes. Collectively, our research provides a comprehensive understanding of the biocontrol potential and soil adaption of L. capsici CK09 and implies the potential of this strain for application in the future.
Collapse
Affiliation(s)
- Pu Yang
- School of Life Science, Shanxi University, Taiyuan 030006, China
| | - Chaofan Qu
- School of Life Science, Shanxi University, Taiyuan 030006, China
| | - Miaomiao Yuan
- School of Life Science, Shanxi University, Taiyuan 030006, China
| | - Bo Xi
- School of Life Science, Shanxi University, Taiyuan 030006, China
| | - Xiu Jia
- Institute of Biodiversity, Faculty of Biological Sciences, Cluster of Excellence Balance of the Microverse, Friedrich Schiller University Jena, 07745 Jena, Germany
| | - Ben Zhang
- School of Life Science, Shanxi University, Taiyuan 030006, China
| | - Lizhen Zhang
- School of Life Science, Shanxi University, Taiyuan 030006, China
| |
Collapse
|
4
|
Nguyen M, Wu TH, Danielson K, Khan N, Zhang J, Craig L. Mechanism of secretion of TcpF by the Vibrio cholerae toxin-coregulated pilus. Proc Natl Acad Sci U S A 2023; 120:e2212664120. [PMID: 37040409 PMCID: PMC10120004 DOI: 10.1073/pnas.2212664120] [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: 07/25/2022] [Accepted: 02/28/2023] [Indexed: 04/12/2023] Open
Abstract
Many bacteria possess dynamic filaments called Type IV pili (T4P) that perform diverse functions in colonization and dissemination, including host cell adhesion, DNA uptake, and secretion of protein substrates-exoproteins-from the periplasm to the extracellular space. The Vibrio cholerae toxin-coregulated pilus (TCP) and the enterotoxigenic Escherichia coli CFA/III pilus each mediates export of a single exoprotein, TcpF and CofJ, respectively. Here, we show that the disordered N-terminal segment of mature TcpF is the export signal (ES) recognized by TCP. Deletion of the ES disrupts secretion and causes TcpF to accumulate in the V. cholerae periplasm. The ES alone can mediate export of Neisseria gonorrhoeae FbpA by V. cholerae in a T4P-dependent manner. The ES is specific for its autologous T4P machinery as CofJ bearing the TcpF ES is exported by V. cholerae, whereas TcpF bearing the CofJ ES is not. Specificity is mediated by binding of the ES to TcpB, a minor pilin that primes pilus assembly and forms a trimer at the pilus tip. Finally, the ES is proteolyzed from the mature TcpF protein upon secretion. Together, these results provide a mechanism for delivery of TcpF across the outer membrane and release into the extracellular space.
Collapse
Affiliation(s)
- Minh Nguyen
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BCV5A 1S6, Canada
| | - Tzu-Hui Wu
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BCV5A 1S6, Canada
| | - Katie J. Danielson
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BCV5A 1S6, Canada
| | - Nabeel M. Khan
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BCV5A 1S6, Canada
| | - John Zhijia Zhang
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BCV5A 1S6, Canada
| | - Lisa Craig
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BCV5A 1S6, Canada
| |
Collapse
|
5
|
Li P, Zhang S, Wang J, Al-Shamiri MM, Han B, Chen Y, Han S, Han L. Uncovering the Secretion Systems of Acinetobacter baumannii: Structures and Functions in Pathogenicity and Antibiotic Resistance. Antibiotics (Basel) 2023; 12:antibiotics12020195. [PMID: 36830106 PMCID: PMC9952577 DOI: 10.3390/antibiotics12020195] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 01/06/2023] [Accepted: 01/16/2023] [Indexed: 01/19/2023] Open
Abstract
Infections led by Acinetobacter baumannii strains are of great concern in healthcare environments due to the strong ability of the bacteria to spread through different apparatuses and develop drug resistance. Severe diseases can be caused by A. baumannii in critically ill patients, but its biological process and mechanism are not well understood. Secretion systems have recently been demonstrated to be involved in the pathogenic process, and five types of secretion systems out of the currently known six from Gram-negative bacteria have been found in A. baumannii. They can promote the fitness and pathogenesis of the bacteria by releasing a variety of effectors. Additionally, antibiotic resistance is found to be related to some types of secretion systems. In this review, we describe the genetic and structural compositions of the five secretion systems that exist in Acinetobacter. In addition, the function and molecular mechanism of each secretion system are summarized to explain how they enable these critical pathogens to overcome eukaryotic hosts and prokaryotic competitors to cause diseases.
Collapse
Affiliation(s)
- Pu Li
- School of Public Health, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
| | - Sirui Zhang
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
| | - Jingdan Wang
- School of Public Health, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
| | - Mona Mohamed Al-Shamiri
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
| | - Bei Han
- School of Public Health, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
| | - Yanjiong Chen
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
| | - Shaoshan Han
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an 710061, China
| | - Lei Han
- Department of Microbiology and Immunology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, Xi’an 710061, China
- Correspondence:
| |
Collapse
|
6
|
Jacobsen T, Dazzoni R, Renault MG, Bardiaux B, Nilges M, Shevchik V, Izadi-Pruneyre N. Secondary structure and 1H, 15 N & 13C resonance assignments of the periplasmic domain of OutG, major pseudopilin from Dickeya dadantii type II secretion system. BIOMOLECULAR NMR ASSIGNMENTS 2022; 16:231-236. [PMID: 35482172 PMCID: PMC9510105 DOI: 10.1007/s12104-022-10085-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 03/30/2022] [Indexed: 06/14/2023]
Abstract
The ability to interact and adapt to the surrounding environment is vital for bacteria that colonise various niches and organisms. One strategy developed by Gram-negative bacteria is to secrete exoprotein substrates via the type II secretion system (T2SS). The T2SS is a proteinaceous complex spanning the bacterial envelope that translocates folded proteins such as toxins and enzymes from the periplasm to the extracellular milieu. In the T2SS, a cytoplasmic ATPase elongates in the periplasm the pseudopilus, a non-covalent polymer composed of protein subunits named pseudopilins, and anchored in the inner membrane by a transmembrane helix. The pseudopilus polymerisation is coupled to the secretion of substrates. The T2SS of Dickeya dadantii secretes more than 15 substrates, essentially plant cell wall degrading enzymes. In D. dadantii, the major pseudopilin or the major subunit of the pseudopilus is called OutG. To better understand the mechanism of secretion of these numerous substrates via the pseudopilus, we have been studying the structure of OutG by NMR. Here, as the first part of this study, we report the 1H, 15N and 13C backbone and sidechain chemical shift assignment of the periplasmic domain of OutG and its NMR derived secondary structure.
Collapse
Affiliation(s)
- Theis Jacobsen
- CNRS UMR3528, Structural Bioinformatics Unit, Institut Pasteur, Université Paris Cité, 75015, Paris, France
- Sorbonne Université, Complexité du Vivant, 75005, Paris, France
| | - Régine Dazzoni
- CNRS UMR3528, Structural Bioinformatics Unit, Institut Pasteur, Université Paris Cité, 75015, Paris, France
| | - Melvin G Renault
- Université Claude Bernard Lyon 1, INSA-Lyon, CNRS, UMR5240 MAP, Microbiologie Adaptation et Pathogénie, 69622, Villeurbanne, France
| | - Benjamin Bardiaux
- CNRS UMR3528, Structural Bioinformatics Unit, Institut Pasteur, Université Paris Cité, 75015, Paris, France
| | - Michael Nilges
- CNRS UMR3528, Structural Bioinformatics Unit, Institut Pasteur, Université Paris Cité, 75015, Paris, France
| | - Vladimir Shevchik
- Université Claude Bernard Lyon 1, INSA-Lyon, CNRS, UMR5240 MAP, Microbiologie Adaptation et Pathogénie, 69622, Villeurbanne, France
| | - Nadia Izadi-Pruneyre
- CNRS UMR3528, Structural Bioinformatics Unit, Institut Pasteur, Université Paris Cité, 75015, Paris, France.
| |
Collapse
|
7
|
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.
Collapse
|
8
|
Hu Y, Zheng J, Zhang J. Natural Transformation in Acinetobacter baumannii W068: A Genetic Analysis Reveals the Involvements of the CRP, XcpV, XcpW, TsaP, and TonB2. Front Microbiol 2022; 12:738034. [PMID: 35126321 PMCID: PMC8811193 DOI: 10.3389/fmicb.2021.738034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 12/14/2021] [Indexed: 01/25/2023] Open
Abstract
Acinetobacter baumannii is a serious threat to public health, and there is increasing attention to the development of antibiotic resistance in this bacterium. Natural transformation is a major horizontal gene transfer mechanism that can lead to antibiotic resistance. To better understand the mechanism of natural transformation in A. baumannii, we selected a clinical isolate that was transformable but had no visible extracellular type IV pili (T4P) filaments and then examined the effects of multiple single-gene knockouts on natural plasmid transformation. Among 33 candidate genes, 28 knockout mutants had severely or completely impaired transformability. Some of these genes had established roles in T4P biogenesis; DNA transfer across the outer membrane, periplasm, or inner membrane; and protection of intracellular single-stranded DNA (ssDNA). Other genes had no previously reported roles in natural transformation of A. baumannii, including competence activator cAMP receptor protein (CRP), a periplasmic protein that may function in T4P assembly (TonB2), a T4P secretin-associated protein (TsaP), and two type II secretion system (T2SS) minor pseudopilus assembly prime complex competent proteins (XcpV and XcpW). The deletion of the T2SS assembly platform protein X had no effect on transformation, and the minor pseudopilins were capable of initiating major pilin assembly. Thus, we speculate that XcpV and XcpW may function in DNA uptake with major pilin assembly, a non-T2SS-dependent mechanism and that a competence pseudopilus similar to T4P constituted the central part of the DNA uptake complex. These results may help guide future research on the alarming increase of antibiotic resistance in this pathogen.
Collapse
Affiliation(s)
- Yuan Hu
- State Key Laboratory of Infectious Disease Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Junjie Zheng
- The Fifth Medical Center of Chinese PLA General Hospital, Beijing, China
| | - Jianzhong Zhang
- State Key Laboratory of Infectious Disease Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
- *Correspondence: Jianzhong Zhang,
| |
Collapse
|
9
|
Budowa i znaczenie II systemu sekrecji białek w ekologii i patogenezie Legionella pneumophila. POSTEP HIG MED DOSW 2021. [DOI: 10.2478/ahem-2021-0034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
Pałeczki Legionella pneumophila pasożytują w komórkach odległych filogenetycznie gospodarzy, w środowisku wodnym w pierwotniakach, a w organizmie człowieka w makrofagach alweolarnych. Zdolność tych bakterii do wewnątrzkomórkowego namnażania się w komórkach fagocytujących, wyspecjalizowanych do niszczenia mikroorganizmów, ma podstawowe znaczenie dla rozwoju nietypowego zapalenia płuc zwanego chorobą legionistów. Umiejscowione na kilku różnych loci chromosomu bakteryjnego geny II systemu sekrecji L. pneumophila kodują co najmniej 25 białek, w tym enzymy o aktywności lipolitycznej, proteolitycznej, rybonukleazy oraz białka unikalne bakterii Legionella. W środowisku naturalnym T2SS L. pneumophila odgrywa decydującą rolę w ekologii tych drobnoustrojów determinując ich zdolność do przeżycia zarówno w postaci planktonicznej, jak i w strukturach biofilmu w słodkowodnych zbiornikach o niskiej temperaturze. Białka T2SS umożliwiają L. pneumophila zakażenie różnych gatunków pierwotniaków, a substraty tego systemu określają zakres pierwotniaczego gospodarza. Namnażanie się bakterii w różnorodnych pierwotniakach przyczynia się do ich rozsiewania oraz transmisji do antropogenicznych źródeł. Białka wydzielane za pomocą II systemu sekrecji determinują również zdolność L. pneumophila do zakażania mysich makrofagów alweolarnych i szpiku kostnego, ludzkich makrofagów linii U937 i THP-1 oraz komórek nabłonkowych pęcherzyków płucnych. Enzymy wydzielane za pomocą tego systemu, takie jak: proteazy, aminopeptydazy czy fosfolipazy umożliwiają pozyskanie substancji pokarmowych oraz powodują destrukcję tkanki płucnej myszy. W organizmie człowieka białka T2SS przyczyniają się do osłabienia wrodzonej odpowiedzi immunologicznej na zakażenie L. pneumophila przez hamowanie indukcji prozapalnych cytokin (IL-6, TNF-α, IL-1 oraz IL-8).
Collapse
|
10
|
Structural interactions define assembly adapter function of a type II secretion system pseudopilin. Structure 2021; 29:1116-1127.e8. [PMID: 34139172 DOI: 10.1016/j.str.2021.05.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 03/15/2021] [Accepted: 05/28/2021] [Indexed: 01/13/2023]
Abstract
The type IV filament superfamily comprises widespread membrane-associated polymers in prokaryotes. The type II secretion system (T2SS), a virulence pathway in many pathogens, belongs to this superfamily. A knowledge gap in understanding of the T2SS is the molecular role of a small "pseudopilin" protein. Using multiple biophysical techniques, we have deciphered how this missing component of the Xcp T2SS architecture is structurally integrated, and thereby unlocked its function. We demonstrate that low-abundance XcpH is the adapter that bridges a trimeric initiating tip complex, XcpIJK, with a periplasmic filament of XcpG subunits. Each pseudopilin protein caps an XcpG protofilament in an overall pseudopilus compatible with dimensions of the periplasm and the outer membrane-spanning secretin through which substrates pass. Unexpectedly, to fulfill its adapter function, the XcpH N-terminal helix must be unwound, a property shared with XcpG subunits. We provide an experimentally validated three-dimensional structural model of a complete type IV filament.
Collapse
|
11
|
Horváthová L, Žárský V, Pánek T, Derelle R, Pyrih J, Motyčková A, Klápšťová V, Vinopalová M, Marková L, Voleman L, Klimeš V, Petrů M, Vaitová Z, Čepička I, Hryzáková K, Harant K, Gray MW, Chami M, Guilvout I, Francetic O, Franz Lang B, Vlček Č, Tsaousis AD, Eliáš M, Doležal P. Analysis of diverse eukaryotes suggests the existence of an ancestral mitochondrial apparatus derived from the bacterial type II secretion system. Nat Commun 2021; 12:2947. [PMID: 34011950 PMCID: PMC8134430 DOI: 10.1038/s41467-021-23046-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Accepted: 03/22/2021] [Indexed: 12/14/2022] Open
Abstract
The type 2 secretion system (T2SS) is present in some Gram-negative eubacteria and used to secrete proteins across the outer membrane. Here we report that certain representative heteroloboseans, jakobids, malawimonads and hemimastigotes unexpectedly possess homologues of core T2SS components. We show that at least some of them are present in mitochondria, and their behaviour in biochemical assays is consistent with the presence of a mitochondrial T2SS-derived system (miT2SS). We additionally identified 23 protein families co-occurring with miT2SS in eukaryotes. Seven of these proteins could be directly linked to the core miT2SS by functional data and/or sequence features, whereas others may represent different parts of a broader functional pathway, possibly also involving the peroxisome. Its distribution in eukaryotes and phylogenetic evidence together indicate that the miT2SS-centred pathway is an ancestral eukaryotic trait. Our findings thus have direct implications for the functional properties of the early mitochondrion. Bacteria use the type 2 secretion system to secrete enzymes and toxins across the outer membrane to the environment. Here the authors analyse the T2SS pathway in three protist lineages and suggest that the early mitochondrion may have been capable of secreting proteins into the cytosol.
Collapse
Affiliation(s)
- Lenka Horváthová
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic
| | - Vojtěch Žárský
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic
| | - Tomáš Pánek
- Faculty of Science, Department of Biology and Ecology, University of Ostrava, Ostrava, Czech Republic.,Faculty of Science, Department of Zoology, Charles University, Prague 2, Czech Republic
| | - Romain Derelle
- School of Biosciences, University of Birmingham, Edgbaston, UK
| | - Jan Pyrih
- Laboratory of Molecular & Evolutionary Parasitology, RAPID group, School of Biosciences, University of Kent, Canterbury, UK.,Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic
| | - Alžběta Motyčková
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic
| | - Veronika Klápšťová
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic
| | - Martina Vinopalová
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic
| | - Lenka Marková
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic
| | - Luboš Voleman
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic
| | - Vladimír Klimeš
- Faculty of Science, Department of Biology and Ecology, University of Ostrava, Ostrava, Czech Republic
| | - Markéta Petrů
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic
| | - Zuzana Vaitová
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic
| | - Ivan Čepička
- Faculty of Science, Department of Zoology, Charles University, Prague 2, Czech Republic
| | - Klára Hryzáková
- Faculty of Science, Department of Genetics and Microbiology, Charles University, Prague 2, Czech Republic
| | - Karel Harant
- Faculty of Science, Proteomic core facility, Charles University, BIOCEV, Vestec, Czech Republic
| | - Michael W Gray
- Department of Biochemistry and Molecular Biology and Centre for Comparative Genomics and Evolutionary Bioinformatics, Dalhousie University, Halifax, NS, Canada
| | - Mohamed Chami
- Center for Cellular Imaging and NanoAnalytics, University of Basel, Basel, Switzerland
| | - Ingrid Guilvout
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, Institut Pasteur, CNRS UMR3528, Paris, France
| | - Olivera Francetic
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, Institut Pasteur, CNRS UMR3528, Paris, France
| | - B Franz Lang
- Robert Cedergren Centre for Bioinformatics and Genomics, Département de Biochimie, Université de Montréal, Montreal, QC, Canada
| | - Čestmír Vlček
- Institute of Molecular Genetics, Czech Academy of Sciences, Prague 4, Czech Republic
| | - Anastasios D Tsaousis
- Laboratory of Molecular & Evolutionary Parasitology, RAPID group, School of Biosciences, University of Kent, Canterbury, UK
| | - Marek Eliáš
- Faculty of Science, Department of Biology and Ecology, University of Ostrava, Ostrava, Czech Republic.
| | - Pavel Doležal
- Faculty of Science, Department of Parasitology, Charles University, BIOCEV, Vestec, Czech Republic.
| |
Collapse
|
12
|
Chauhan D, Shames SR. Pathogenicity and Virulence of Legionella: Intracellular replication and host response. Virulence 2021; 12:1122-1144. [PMID: 33843434 PMCID: PMC8043192 DOI: 10.1080/21505594.2021.1903199] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Bacteria of the genus Legionella are natural pathogens of amoebae that can cause a severe pneumonia in humans called Legionnaires’ Disease. Human disease results from inhalation of Legionella-contaminated aerosols and subsequent bacterial replication within alveolar macrophages. Legionella pathogenicity in humans has resulted from extensive co-evolution with diverse genera of amoebae. To replicate intracellularly, Legionella generates a replication-permissive compartment called the Legionella-containing vacuole (LCV) through the concerted action of hundreds of Dot/Icm-translocated effector proteins. In this review, we present a collective overview of Legionella pathogenicity including infection mechanisms, secretion systems, and translocated effector function. We also discuss innate and adaptive immune responses to L. pneumophila, the implications of Legionella genome diversity and future avenues for the field.
Collapse
Affiliation(s)
- Deepika Chauhan
- Division of Biology, Kansas State University, Manhattan, Kansas, USA
| | | |
Collapse
|
13
|
Pineau C, Guschinskaya N, Gonçalves IR, Ruaudel F, Robert X, Gouet P, Ballut L, Shevchik VE. Structure-function analysis of pectate lyase Pel3 reveals essential facets of protein recognition by the bacterial type 2 secretion system. J Biol Chem 2021; 296:100305. [PMID: 33465378 PMCID: PMC7949064 DOI: 10.1016/j.jbc.2021.100305] [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: 11/10/2020] [Revised: 01/11/2021] [Accepted: 01/14/2021] [Indexed: 12/02/2022] Open
Abstract
The type II secretion system (T2SS) transports fully folded proteins of various functions and structures through the outer membrane of Gram-negative bacteria. The molecular mechanisms of substrate recruitment by T2SS remain elusive but a prevailing view is that the secretion determinants could be of a structural nature. The phytopathogenic γ-proteobacteria, Pectobacterium carotovorum and Dickeya dadantii, secrete similar sets of homologous plant cell wall degrading enzymes, mainly pectinases, by similar T2SSs, called Out. However, the orthologous pectate lyases Pel3 and PelI from these bacteria, which share 67% of sequence identity, are not secreted by the counterpart T2SS of each bacterium, indicating a fine-tuned control of protein recruitment. To identify the related secretion determinants, we first performed a structural characterization and comparison of Pel3 with PelI using X-ray crystallography. Then, to assess the biological relevance of the observed structural variations, we conducted a loop-substitution analysis of Pel3 combined with secretion assays. We showed that there is not one element with a definite secondary structure but several distant and structurally flexible loop regions that are essential for the secretion of Pel3 and that these loop regions act together as a composite secretion signal. Interestingly, depending on the crystal contacts, one of these key secretion determinants undergoes disorder-to-order transitions that could reflect its transient structuration upon the contact with the appropriate T2SS components. We hypothesize that such T2SS-induced structuration of some intrinsically disordered zones of secretion substrates could be part of the recruitment mechanism used by T2SS.
Collapse
Affiliation(s)
- Camille Pineau
- Microbiologie Adaptation et Pathogénie, Univ Lyon, Université de Lyon 1, UMR5240 CNRS, Villeurbanne, France; Microbiologie Adaptation et Pathogénie, Univ Lyon, INSA Lyon, UMR5240, Villeurbanne, France
| | - Natalia Guschinskaya
- Microbiologie Adaptation et Pathogénie, Univ Lyon, Université de Lyon 1, UMR5240 CNRS, Villeurbanne, France; Microbiologie Adaptation et Pathogénie, Univ Lyon, INSA Lyon, UMR5240, Villeurbanne, France
| | - Isabelle R Gonçalves
- Microbiologie Adaptation et Pathogénie, Univ Lyon, Université de Lyon 1, UMR5240 CNRS, Villeurbanne, France
| | - Florence Ruaudel
- Microbiologie Adaptation et Pathogénie, Univ Lyon, Université de Lyon 1, UMR5240 CNRS, Villeurbanne, France
| | - Xavier Robert
- Molecular Microbiology and Structural Biochemistry, Univ Lyon, UMR5086 CNRS, Lyon, France
| | - Patrice Gouet
- Molecular Microbiology and Structural Biochemistry, Univ Lyon, UMR5086 CNRS, Lyon, France
| | - Lionel Ballut
- Molecular Microbiology and Structural Biochemistry, Univ Lyon, UMR5086 CNRS, Lyon, France.
| | - Vladimir E Shevchik
- Microbiologie Adaptation et Pathogénie, Univ Lyon, Université de Lyon 1, UMR5240 CNRS, Villeurbanne, France; Microbiologie Adaptation et Pathogénie, Univ Lyon, INSA Lyon, UMR5240, Villeurbanne, France.
| |
Collapse
|
14
|
Suppressor Mutations in Type II Secretion Mutants of Vibrio cholerae: Inactivation of the VesC Protease. mSphere 2020; 5:5/6/e01125-20. [PMID: 33328352 PMCID: PMC7771236 DOI: 10.1128/msphere.01125-20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Genome-wide transposon mutagenesis has identified the genes encoding the T2SS in Vibrio cholerae as essential for viability, but the reason for this is unclear. Mutants with deletions or insertions in these genes can be isolated, suggesting that they have acquired secondary mutations that suppress their growth defect. The type II secretion system (T2SS) is a conserved transport pathway responsible for the secretion of a range of virulence factors by many pathogens, including Vibrio cholerae. Disruption of the T2SS genes in V. cholerae results in loss of secretion, changes in cell envelope function, and growth defects. While T2SS mutants are viable, high-throughput genomic analyses have listed these genes among essential genes. To investigate whether secondary mutations arise as a consequence of T2SS inactivation, we sequenced the genomes of six V. cholerae T2SS mutants with deletions or insertions in either the epsG, epsL, or epsM genes and identified secondary mutations in all mutants. Two of the six T2SS mutants contain distinct mutations in the gene encoding the T2SS-secreted protease VesC. Other mutations were found in genes coding for V. cholerae cell envelope proteins. Subsequent sequence analysis of the vesC gene in 92 additional T2SS mutant isolates identified another 19 unique mutations including insertions or deletions, sequence duplications, and single-nucleotide changes resulting in amino acid substitutions in the VesC protein. Analysis of VesC variants and the X-ray crystallographic structure of wild-type VesC suggested that all mutations lead to loss of VesC production and/or function. One possible mechanism by which V. cholerae T2SS mutagenesis can be tolerated is through selection of vesC-inactivating mutations, which may, in part, suppress cell envelope damage, establishing permissive conditions for the disruption of the T2SS. Other mutations may have been acquired in genes encoding essential cell envelope proteins to prevent proteolysis by VesC. IMPORTANCE Genome-wide transposon mutagenesis has identified the genes encoding the T2SS in Vibrio cholerae as essential for viability, but the reason for this is unclear. Mutants with deletions or insertions in these genes can be isolated, suggesting that they have acquired secondary mutations that suppress their growth defect. Through whole-genome sequencing and phenotypic analysis of T2SS mutants, we show that one means by which the growth defect can be suppressed is through mutations in the gene encoding the T2SS substrate VesC. VesC homologues are present in other Vibrio species and close relatives, and this may be why inactivation of the T2SS in species such as Vibrio vulnificus, Vibrio sp. strain 60, and Aeromonas hydrophila also results in a pleiotropic effect on their outer membrane assembly and integrity.
Collapse
|
15
|
Portlock TJ, Tyson JY, Dantu SC, Rehman S, White RC, McIntire IE, Sewell L, Richardson K, Shaw R, Pandini A, Cianciotto NP, Garnett JA. Structure, Dynamics and Cellular Insight Into Novel Substrates of the Legionella pneumophila Type II Secretion System. Front Mol Biosci 2020; 7:112. [PMID: 32656228 PMCID: PMC7325957 DOI: 10.3389/fmolb.2020.00112] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 05/12/2020] [Indexed: 12/13/2022] Open
Abstract
Legionella pneumophila is a Gram-negative bacterium that is able to replicate within a broad range of aquatic protozoan hosts. L. pneumophila is also an opportunistic human pathogen that can infect macrophages and epithelia in the lung and lead to Legionnaires’ disease. The type II secretion system is a key virulence factor of L. pneumophila and is used to promote bacterial growth at low temperatures, regulate biofilm formation, modulate host responses to infection, facilitate bacterial penetration of mucin gels and is necessary for intracellular growth during the initial stages of infection. The L. pneumophila type II secretion system exports at least 25 substrates out of the bacterium and several of these, including NttA to NttG, contain unique amino acid sequences that are generally not observed outside of the Legionella genus. NttA, NttC, and NttD are required for infection of several amoebal species but it is unclear what influence other novel substrates have within their host. In this study, we show that NttE is required for optimal infection of Acanthamoeba castellanii and Vermamoeba vermiformis amoeba and is essential for the typical colony morphology of L. pneumophila. In addition, we report the atomic structures of NttA, NttC, and NttE and through a combined biophysical and biochemical hypothesis driven approach we propose novel functions for these substrates during infection. This work lays the foundation for future studies into the mechanistic understanding of novel type II substrate functions and how these relate to L. pneumophila ecology and disease.
Collapse
Affiliation(s)
- Theo J Portlock
- Centre for Host-Microbiome Interactions, Dental Institute, King's College London, London, United Kingdom.,Department of Chemistry and Biochemistry, School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom
| | - Jessica Y Tyson
- Department of Microbiology and Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Sarath C Dantu
- Department of Computer Science, Brunel University London, Uxbridge, United Kingdom
| | - Saima Rehman
- Centre for Host-Microbiome Interactions, Dental Institute, King's College London, London, United Kingdom
| | - Richard C White
- Department of Microbiology and Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Ian E McIntire
- Department of Microbiology and Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Lee Sewell
- Centre for Host-Microbiome Interactions, Dental Institute, King's College London, London, United Kingdom
| | - Katherine Richardson
- Department of Chemistry and Biochemistry, School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom
| | - Rosie Shaw
- Department of Chemistry and Biochemistry, School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom
| | - Alessandro Pandini
- Department of Computer Science, Brunel University London, Uxbridge, United Kingdom
| | - Nicholas P Cianciotto
- Department of Microbiology and Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - James A Garnett
- Centre for Host-Microbiome Interactions, Dental Institute, King's College London, London, United Kingdom.,Department of Chemistry and Biochemistry, School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom
| |
Collapse
|
16
|
Craig L, Forest KT, Maier B. Type IV pili: dynamics, biophysics and functional consequences. Nat Rev Microbiol 2020; 17:429-440. [PMID: 30988511 DOI: 10.1038/s41579-019-0195-4] [Citation(s) in RCA: 212] [Impact Index Per Article: 53.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The surfaces of many bacteria are decorated with long, exquisitely thin appendages called type IV pili (T4P), dynamic filaments that are rapidly polymerized and depolymerized from a pool of pilin subunits. Cycles of pilus extension, binding and retraction enable T4P to perform a phenomenally diverse array of functions, including twitching motility, DNA uptake and microcolony formation. On the basis of recent developments, a comprehensive understanding is emerging of the molecular architecture of the T4P machinery and the filament it builds, providing mechanistic insights into the assembly and retraction processes. Combined microbiological and biophysical approaches have revealed how T4P dynamics influence self-organization of bacteria, how bacteria respond to external stimuli to regulate T4P activity for directed movement, and the role of T4P retraction in surface sensing. In this Review, we discuss the T4P machine architecture and filament structure and present current molecular models for T4P dynamics, with a particular focus on recent insights into T4P retraction. We also discuss the functional consequences of T4P dynamics, which have important implications for bacterial lifestyle and pathogenesis.
Collapse
Affiliation(s)
- Lisa Craig
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada.
| | - Katrina T Forest
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA.
| | - Berenike Maier
- Institute for Biological Physics, University of Cologne, Köln, Germany.
| |
Collapse
|
17
|
Silva YRDO, Contreras-Martel C, Macheboeuf P, Dessen A. Bacterial secretins: Mechanisms of assembly and membrane targeting. Protein Sci 2020; 29:893-904. [PMID: 32020694 DOI: 10.1002/pro.3835] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 01/25/2020] [Accepted: 01/28/2020] [Indexed: 12/20/2022]
Abstract
Secretion systems are employed by bacteria to transport macromolecules across membranes without compromising their integrities. Processes including virulence, colonization, and motility are highly dependent on the secretion of effector molecules toward the immediate cellular environment, and in some cases, into the host cytoplasm. In Type II and Type III secretion systems, as well as in Type IV pili, homomultimeric complexes known as secretins form large pores in the outer bacterial membrane, and the localization and assembly of such 1 MDa molecules often relies on pilotins or accessory proteins. Significant progress has been made toward understanding details of interactions between secretins and their partner proteins using approaches ranging from bacterial genetics to cryo electron microscopy. This review provides an overview of the mode of action of pilotins and accessory proteins for T2SS, T3SS, and T4PS secretins, highlighting recent near-atomic resolution cryo-EM secretin complex structures and underlining the importance of these interactions for secretin functionality.
Collapse
Affiliation(s)
- Yuri Rafael de Oliveira Silva
- Brazilian Biosciences National Laboratory (LNBio), CNPEM, Campinas, São Paulo, Brazil.,Departamento de Genética, Evolução, Microbiologia e Imunologia, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), Campinas, São Paulo, Brazil
| | - Carlos Contreras-Martel
- Université Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), Grenoble, France
| | - Pauline Macheboeuf
- Université Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), Grenoble, France
| | - Andréa Dessen
- Brazilian Biosciences National Laboratory (LNBio), CNPEM, Campinas, São Paulo, Brazil.,Université Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), Grenoble, France
| |
Collapse
|
18
|
Chen C, Kawamoto J, Kawai S, Tame A, Kato C, Imai T, Kurihara T. Isolation of a Novel Bacterial Strain Capable of Producing Abundant Extracellular Membrane Vesicles Carrying a Single Major Cargo Protein and Analysis of Its Transport Mechanism. Front Microbiol 2020; 10:3001. [PMID: 32010084 PMCID: PMC6971210 DOI: 10.3389/fmicb.2019.03001] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 12/12/2019] [Indexed: 11/13/2022] Open
Abstract
Extracellular membrane vesicles (EMVs) play an important role in various bacterial activities. EMVs have potential for use as vaccines, drug-delivery vehicles, platforms for extracellular production of recombinant proteins, and so on. In this study, we newly isolated a cold-adapted bacterium, Shewanella vesiculosa HM13, which abundantly produces EMVs, characterized them, and analyzed their cargo transport mechanism. S. vesiculosa HM13, isolated from the intestine of a horse mackerel as a prospective host for a low-temperature secretory protein expression system, produced a single major secretory protein, P49, of unknown function in the culture supernatant. Analysis using sucrose density gradient ultracentrifugation indicated that P49 is a cargo protein carried by EMVs. S. vesiculosa HM13 displayed extensive blebbing on the surface of the outer membrane, and the size of blebs was comparable to that of EMVs. These blebs are thought to be precursors of the EMVs. Disruption of the P49 gene resulted in only a marginal decrease in the EMV production, indicating that the EMVs are produced even in the absence of the major cargo protein. Whole genome sequencing of S. vesiculosa HM13 revealed that this bacterium has a gene cluster coding for a non-canonical type II protein secretion system (T2SS) homolog in addition to a gene cluster coding for canonical T2SS. The P49 gene was located downstream of the former gene cluster. To examine the role of the putative non-canonical T2SS-like translocon, we disrupted the gene coding for a putative outer membrane channel of the translocon, named GspD2. The gspD2 disruption lead to disappearance of P49 in the EMV fraction, whereas the production of EMVs was not significantly affected by this mutation. These results are indicative that the T2SS-like machinery functions as a novel type of protein translocon responsible for selective cargo loading to the EMVs. We also found that GFP fused to the C-terminus of P49 expressed in S. vesiculosa HM13 was transported to EMVs, indicating that P49 is useful as a carrier to deliver the fusion partner to EMVs. These findings deepen our understanding of the mechanism of biogenesis of EMVs and facilitate their applications.
Collapse
Affiliation(s)
- Chen Chen
- Institute for Chemical Research, Kyoto University, Uji, Japan
| | - Jun Kawamoto
- Institute for Chemical Research, Kyoto University, Uji, Japan
| | - Soichiro Kawai
- Institute for Chemical Research, Kyoto University, Uji, Japan
| | | | - Chiaki Kato
- Department of Marine Biodiversity Research, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
| | - Tomoya Imai
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Japan
| | - Tatsuo Kurihara
- Institute for Chemical Research, Kyoto University, Uji, Japan
| |
Collapse
|
19
|
Ghosal D, Kim KW, Zheng H, Kaplan M, Truchan HK, Lopez AE, McIntire IE, Vogel JP, Cianciotto NP, Jensen GJ. In vivo structure of the Legionella type II secretion system by electron cryotomography. Nat Microbiol 2019; 4:2101-2108. [PMID: 31754273 PMCID: PMC6879910 DOI: 10.1038/s41564-019-0603-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2019] [Accepted: 10/07/2019] [Indexed: 12/12/2022]
Abstract
The type II secretion system (T2SS) is a multiprotein envelope-spanning assembly that translocates a wide range of virulence factors, enzymes and effectors through the outer membrane of many Gram-negative bacteria1-3. Here, using electron cryotomography and subtomogram averaging methods, we reveal the in vivo structure of an intact T2SS imaged within the human pathogen Legionella pneumophila. Although the T2SS has only limited sequence and component homology with the evolutionarily related type IV pilus (T4P) system4,5, we show that their overall architectures are remarkably similar. Despite similarities, there are also differences, including, for example, that the T2SS-ATPase complex is usually present but disengaged from the inner membrane, the T2SS has a much longer periplasmic vestibule and it has a short-lived flexible pseudopilus. Placing atomic models of the components into our electron cryotomography map produced a complete architectural model of the intact T2SS that provides insights into the structure and function of its components, its position within the cell envelope and the interactions between its different subcomplexes.
Collapse
Affiliation(s)
- Debnath Ghosal
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Ki Woo Kim
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
- School of Ecology and Environmental System, Kyungpook National University, Sangju, Korea
| | - Huaixin Zheng
- Department of Microbiology and Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
- Department of Immunology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou City, Henan Province, China
| | - Mohammed Kaplan
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Hilary K Truchan
- Department of Microbiology and Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Alberto E Lopez
- Department of Microbiology and Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Ian E McIntire
- Department of Microbiology and Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Joseph P Vogel
- Department of Molecular Microbiology, Washington University School of Medicine, St Louis, MO, USA
| | - Nicholas P Cianciotto
- Department of Microbiology and Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Grant J Jensen
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA.
- Howard Hughes Medical Institute, Pasadena, CA, USA.
| |
Collapse
|
20
|
Jacobsen T, Bardiaux B, Francetic O, Izadi-Pruneyre N, Nilges M. Structure and function of minor pilins of type IV pili. Med Microbiol Immunol 2019; 209:301-308. [PMID: 31784891 PMCID: PMC7248040 DOI: 10.1007/s00430-019-00642-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Accepted: 11/14/2019] [Indexed: 02/06/2023]
Abstract
Type IV pili are versatile and highly flexible fibers formed on the surface of many Gram-negative and Gram-positive bacteria. Virulence and infection rate of several pathogenic bacteria, such as Neisseria meningitidis and Pseudomonas aeruginosa, are strongly dependent on the presence of pili as they facilitate the adhesion of the bacteria to the host cell. Disruption of the interactions between the pili and the host cells by targeting proteins involved in this interaction could, therefore, be a treatment strategy. A type IV pilus is primarily composed of multiple copies of protein subunits called major pilins. Additional proteins, called minor pilins, are present in lower abundance, but are essential for the assembly of the pilus or for its specific functions. One class of minor pilins is required to initiate the formation of pili, and may form a complex similar to that identified in the related type II secretion system. Other, species-specific minor pilins in the type IV pilus system have been shown to promote additional functions such as DNA binding, aggregation and adherence. Here, we will review the structure and the function of the minor pilins from type IV pili.
Collapse
Affiliation(s)
- Theis Jacobsen
- Structural Bioinformatics Unit, Department of Structural Biology and Chemistry, C3BI, Institut Pasteur, CNRS UMR3528, CNRS USR3756, Paris, France.,Sorbonne Université, Complexité du Vivant, 75005, Paris, France
| | - Benjamin Bardiaux
- Structural Bioinformatics Unit, Department of Structural Biology and Chemistry, C3BI, Institut Pasteur, CNRS UMR3528, CNRS USR3756, Paris, France
| | - Olivera Francetic
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, Institut Pasteur, CNRS UMR3528, Paris, France
| | - Nadia Izadi-Pruneyre
- Structural Bioinformatics Unit, Department of Structural Biology and Chemistry, C3BI, Institut Pasteur, CNRS UMR3528, CNRS USR3756, Paris, France
| | - Michael Nilges
- Structural Bioinformatics Unit, Department of Structural Biology and Chemistry, C3BI, Institut Pasteur, CNRS UMR3528, CNRS USR3756, Paris, France.
| |
Collapse
|
21
|
Bardiaux B, Cordier F, Brier S, López-Castilla A, Izadi-Pruneyre N, Nilges M. Dynamics of a type 2 secretion system pseudopilus unraveled by complementary approaches. JOURNAL OF BIOMOLECULAR NMR 2019; 73:293-303. [PMID: 31124002 PMCID: PMC6692295 DOI: 10.1007/s10858-019-00246-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 04/10/2019] [Indexed: 06/09/2023]
Abstract
Secretion pili, bacterial fibers responsible for transporting proteins to the extracellular milieu in some secretion systems, are very strong structures but at the same time highly flexible. Their flexibility and helical symmetry make structure determination at atomic resolution a challenging task. We have previously used an integrative structural biology approach including liquid-state NMR, cryo-electron microscopy (cryo-EM), and modeling to determine the pseudo-atomic resolution structure of the type 2 secretion system pseudopilus in a mutant form, where we employed NMR to determine the high resolution structure of the pilin (the monomer building block of the pilus). In this work, we determine the pseudo-atomic structure of the wild type pilus, and compare the dynamics of wild type and mutant pili by normal mode analysis. We present a detailed NMR analysis of the dynamics of the pilin in isolation, and compare dynamics and solvent accessibility of isolated and assembled pilins by Hydrogen/Deuterium eXchange Mass Spectrometry (HDX-MS). These complementary approaches provide a comprehensive view of internal and overall dynamics of pili, crucial for their function.
Collapse
Affiliation(s)
- Benjamin Bardiaux
- Structural Bioinformatics Unit, Department of Structural Biology and Chemistry, C3BI, Institut Pasteur; CNRS UMR3528; CNRS USR3756, Paris, France
| | - Florence Cordier
- Structural Bioinformatics Unit, Department of Structural Biology and Chemistry, C3BI, Institut Pasteur; CNRS UMR3528; CNRS USR3756, Paris, France
- Biological NMR Technological Platform, Center for Technological Resources and Research, Department of Structural Biology and Chemistry, Institut Pasteur; CNRS UMR3528, Paris, France
| | - Sébastien Brier
- Biological NMR Technological Platform, Center for Technological Resources and Research, Department of Structural Biology and Chemistry, Institut Pasteur; CNRS UMR3528, Paris, France
| | - Aracelys López-Castilla
- Structural Bioinformatics Unit, Department of Structural Biology and Chemistry, C3BI, Institut Pasteur; CNRS UMR3528; CNRS USR3756, Paris, France
| | - Nadia Izadi-Pruneyre
- Structural Bioinformatics Unit, Department of Structural Biology and Chemistry, C3BI, Institut Pasteur; CNRS UMR3528; CNRS USR3756, Paris, France.
| | - Michael Nilges
- Structural Bioinformatics Unit, Department of Structural Biology and Chemistry, C3BI, Institut Pasteur; CNRS UMR3528; CNRS USR3756, Paris, France.
| |
Collapse
|
22
|
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.
Collapse
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
| |
Collapse
|
23
|
Oikonomou CM, Jensen GJ. Electron Cryotomography of Bacterial Secretion Systems. Microbiol Spectr 2019; 7:10.1128/microbiolspec.PSIB-0019-2018. [PMID: 30953431 PMCID: PMC6452891 DOI: 10.1128/microbiolspec.psib-0019-2018] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Indexed: 02/08/2023] Open
Abstract
In biology, function arises from form. For bacterial secretion systems, which often span two membranes, avidly bind to the cell wall, and contain hundreds of individual proteins, studying form is a daunting task, made possible by electron cryotomography (ECT). ECT is the highest-resolution imaging technique currently available to visualize unique objects inside cells, providing a three-dimensional view of the shapes and locations of large macromolecular complexes in their native environment. Over the past 15 years, ECT has contributed to the study of bacterial secretion systems in two main ways: by revealing intact forms for the first time and by mapping components into these forms. Here we highlight some of these contributions, revealing structural convergence in type II secretion systems, structural divergence in type III secretion systems, unexpected structures in type IV secretion systems, and unexpected mechanisms in types V and VI secretion systems. Together, they offer a glimpse into a world of fantastic forms-nanoscale rotors, needles, pumps, and dart guns-much of which remains to be explored.
Collapse
Affiliation(s)
- Catherine M. Oikonomou
- Department of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Grant J. Jensen
- Department of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
- Howard Hughes Medical Institute, Pasadena, CA, USA
| |
Collapse
|
24
|
Luna-Rico A, Thomassin JL, Francetic O. Analysis of Bacterial Pilus Assembly by Shearing and Immunofluorescence Microscopy. Methods Mol Biol 2019; 1764:291-305. [PMID: 29605922 DOI: 10.1007/978-1-4939-7759-8_18] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Bacterial surface appendages of the type 4 pilus superfamily play diverse roles in adherence, aggregation, motility, signaling, and macromolecular transport. Here we describe two analytical approaches to study assembly of type 4 pili and of pseudopili produced by type 2 protein secretion systems: the shearing assay and immunofluorescence microscopy. These complementary antibody-based methods allow for semiquantitative analysis of fiber assembly. The shearing assay can be scaled up to yield crude extracts of pili that can be further analyzed by electron and atomic force microscopy or by mass spectrometry.
Collapse
Affiliation(s)
- Areli Luna-Rico
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, CNRS UMR3528, Institut Pasteur, Paris Cedex 15, France
| | - Jenny-Lee Thomassin
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, CNRS UMR3528, Institut Pasteur, Paris Cedex 15, France
| | - Olivera Francetic
- Biochemistry of Macromolecular Interactions Unit, Department of Structural Biology and Chemistry, CNRS UMR3528, Institut Pasteur, Paris Cedex 15, France.
| |
Collapse
|
25
|
CpaA Is a Glycan-Specific Adamalysin-like Protease Secreted by Acinetobacter baumannii That Inactivates Coagulation Factor XII. mBio 2018; 9:mBio.01606-18. [PMID: 30563903 PMCID: PMC6299215 DOI: 10.1128/mbio.01606-18] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Ventilator-associated pneumonia and catheter-related bacteremia are the most common and severe infections caused by Acinetobacter baumannii. Besides the capsule, lipopolysaccharides, and the outer membrane porin OmpA, little is known about the contribution of secreted proteins to A. baumannii survival in vivo. Here we focus on CpaA, a potentially recently acquired virulence factor that inhibits blood coagulation in vitro. We identify coagulation factor XII as a target of CpaA, map the cleavage sites, and show that glycosylation is a prerequisite for CpaA-mediated inactivation of factor XII. We propose adding CpaA to a small, but growing list of bacterial proteases that are specific for highly glycosylated components of the host defense system. Antibiotic-resistant Acinetobacter baumannii is increasingly recognized as a cause of difficult-to-treat nosocomial infections, including pneumonia, wound infections, and bacteremia. Previous studies have demonstrated that the metalloprotease CpaA contributes to virulence and prolongs clotting time when added to human plasma as measured by the activated partial thromboplastin time (aPTT) assay. Here, we show that CpaA interferes with the intrinsic coagulation pathway, also called the contact activation system, in human as well as murine plasma, but has no discernible effect on the extrinsic pathway. By utilizing a modified aPTT assay, we demonstrate that coagulation factor XII (fXII) is a target of CpaA. In addition, we map the cleavage by CpaA to two positions, 279-280 and 308-309, within the highly glycosylated proline-rich region of human fXII, and show that cleavage at the 308-309 site is responsible for inactivation of fXII. At both sites, cleavage occurs between proline and an O-linked glycosylated threonine, and deglycosylation of fXII prevents cleavage by CpaA. Consistent with this, mutant fXII (fXII-Thr309Lys) from patients with hereditary angioedema type III (HAEIII) is protected from CpaA inactivation. This raises the possibility that individuals with HAEIII who harbor this mutation may be partially protected from A. baumannii infection if CpaA contributes to human disease. By inactivating fXII, CpaA may attenuate important antimicrobial defense mechanisms such as intravascular thrombus formation, thus allowing A. baumannii to disseminate.
Collapse
|
26
|
Fulara A, Vandenberghe I, Read RJ, Devreese B, Savvides SN. Structure and oligomerization of the periplasmic domain of GspL from the type II secretion system of Pseudomonas aeruginosa. Sci Rep 2018; 8:16760. [PMID: 30425318 PMCID: PMC6233222 DOI: 10.1038/s41598-018-34956-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 10/27/2018] [Indexed: 01/12/2023] Open
Abstract
The ability of bacteria to infect a host relies in part on the secretion of molecular virulence factors across the cell envelope. Pseudomonas aeruginosa, a ubiquitous environmental bacterium causing opportunistic infections in humans, employs the type II secretion system (T2SS) to transport effector proteins across its cellular envelope as part of a diverse array of virulence strategies. General secretory pathway protein L (GspL) is an essential inner-membrane component of the T2SS apparatus, and is thought to facilitate transduction of the energy from ATP hydrolysis in the cytoplasm to the periplasmic components of the system. However, our incomplete understanding of the assembly principles of the T2SS machinery prevents the mechanistic deconvolution of T2SS-mediated protein secretion. Here we show via two crystal structures that the periplasmic ferredoxin-like domain of GspL (GspLfld) is a dimer stabilized by hydrophobic interactions, and that this interface may allow significant interdomain plasticity. The general dimerization mode of GspLfld is shared with GspL from Vibrio parahaemolyticus suggesting a conserved oligomerization mode across the GspL family. Furthermore, we identified a tetrameric form of the complete periplasmic segment of GspL (GspLperi) which indicates that GspL may be able to adopt multiple oligomeric states as part of its dynamic role in the T2SS apparatus.
Collapse
Affiliation(s)
- Aleksandra Fulara
- Unit for Structural Biology, Department of Biochemistry and Microbiology, Ghent University, 9052, Ghent (Zwijnaarde), Belgium
- VIB-UGent Center for Inflammation Research, 9052, Ghent (Zwijnaarde), Belgium
| | - Isabel Vandenberghe
- Laboratory for Microbiology, Department of Biochemistry and Microbiology, Ghent University, 9000, Ghent, Belgium
| | - Randy J Read
- Department of Haematology, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, CB2 0XY, United Kingdom
| | - Bart Devreese
- Laboratory for Microbiology, Department of Biochemistry and Microbiology, Ghent University, 9000, Ghent, Belgium
| | - Savvas N Savvides
- Unit for Structural Biology, Department of Biochemistry and Microbiology, Ghent University, 9052, Ghent (Zwijnaarde), Belgium.
- VIB-UGent Center for Inflammation Research, 9052, Ghent (Zwijnaarde), Belgium.
| |
Collapse
|
27
|
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.
Collapse
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:
| |
Collapse
|
28
|
Michel-Souzy S, Douzi B, Cadoret F, Raynaud C, Quinton L, Ball G, Voulhoux R. Direct interactions between the secreted effector and the T2SS components GspL and GspM reveal a new effector-sensing step during type 2 secretion. J Biol Chem 2018; 293:19441-19450. [PMID: 30337370 DOI: 10.1074/jbc.ra117.001127] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2017] [Revised: 10/04/2018] [Indexed: 12/11/2022] Open
Abstract
In many Gram-negative bacteria, the type 2 secretion system (T2SS) plays an important role in virulence because of its capacity to deliver a large amount of fully folded protein effectors to the extracellular milieu. Despite our knowledge of most T2SS components, the mechanisms underlying effector recruitment and secretion by the T2SS remain enigmatic. Using complementary biophysical and biochemical approaches, we identified here two direct interactions between the secreted effector CbpD and two components, XcpYL and XcpZM, of the T2SS assembly platform (AP) in the opportunistic pathogen Pseudomonas aeruginosa Competition experiments indicated that CbpD binding to XcpYL is XcpZM-dependent, suggesting sequential recruitment of the effector by the periplasmic domains of these AP components. Using a bacterial two-hybrid system, we then tested the influence of the effector on the AP protein-protein interaction network. Our findings revealed that the presence of the effector modifies the AP interactome and, in particular, induces XcpZM homodimerization and increases the affinity between XcpYL and XcpZM The observed direct relationship between effector binding and T2SS dynamics suggests an additional synchronizing step during the type 2 secretion process, where the activation of the AP of the T2SS nanomachine is triggered by effector binding.
Collapse
Affiliation(s)
- Sandra Michel-Souzy
- From the CNRS, Aix Marseille Université, Institut de Microbiologie de la Méditerranée (IMM), Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM)/UMR7255, 13009 Marseille, France
| | - Badreddine Douzi
- From the CNRS, Aix Marseille Université, Institut de Microbiologie de la Méditerranée (IMM), Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM)/UMR7255, 13009 Marseille, France.,CNRS, Aix Marseille Université, IMM, Laboratoire de Chimie Bactérienne (LCB)/UMR7283, 13009 Marseille, France, and
| | - Frédéric Cadoret
- From the CNRS, Aix Marseille Université, Institut de Microbiologie de la Méditerranée (IMM), Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM)/UMR7255, 13009 Marseille, France
| | - Claire Raynaud
- From the CNRS, Aix Marseille Université, Institut de Microbiologie de la Méditerranée (IMM), Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM)/UMR7255, 13009 Marseille, France.,CNRS, Aix Marseille Université, IMM, Laboratoire de Chimie Bactérienne (LCB)/UMR7283, 13009 Marseille, France, and
| | - Loïc Quinton
- Laboratory of Mass Spectrometry-MolSys, Department of Chemistry, University of Liège, B4000 Liège, Belgium
| | - Geneviève Ball
- From the CNRS, Aix Marseille Université, Institut de Microbiologie de la Méditerranée (IMM), Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM)/UMR7255, 13009 Marseille, France.,CNRS, Aix Marseille Université, IMM, Laboratoire de Chimie Bactérienne (LCB)/UMR7283, 13009 Marseille, France, and
| | - Romé Voulhoux
- From the CNRS, Aix Marseille Université, Institut de Microbiologie de la Méditerranée (IMM), Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM)/UMR7255, 13009 Marseille, France, .,CNRS, Aix Marseille Université, IMM, Laboratoire de Chimie Bactérienne (LCB)/UMR7283, 13009 Marseille, France, and
| |
Collapse
|
29
|
Structural cycle of the Thermus thermophilus PilF ATPase: the powering of type IVa pilus assembly. Sci Rep 2018; 8:14022. [PMID: 30232337 PMCID: PMC6145873 DOI: 10.1038/s41598-018-32218-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 08/28/2018] [Indexed: 11/20/2022] Open
Abstract
Type IV pili are responsible for a diverse range of functions, including twitching motility and cell adhesion. Assembly of the pilus fiber is driven by a cytoplasmic ATPase: it interacts with an inner membrane complex of biogenesis proteins which, in turn, bind to nascent pilin subunits and mediate fiber assembly. Here we report the structural characterization of the PilF TFP assembly ATPase from Thermus thermophilus. The crystal structure of a recombinant C-terminal fragment of PilF revealed bound, unhydrolysed ATP, although the full length complex was enzymatically active. 3D reconstructions were carried out by single particle cryoelectron microscopy for full length apoprotein PilF and in complex with AMPPNP. The structure forms an hourglass-like shape, with the ATPase domains in one half and the N1 domains in the second half which, we propose, interact with the other pilus biogenesis components. Molecular models for both forms were generated: binding of AMPPNP causes an upward shift of the N1 domains towards the ATPase domains of ~8 Å. We advocate a model in which ATP hydrolysis is linked to displacement of the N1 domains which is associated with lifting pilin subunits out of the inner membrane, and provide the activation energy needed to form the pilus fiber.
Collapse
|
30
|
Kooger R, Szwedziak P, Böck D, Pilhofer M. CryoEM of bacterial secretion systems. Curr Opin Struct Biol 2018; 52:64-70. [PMID: 30223223 DOI: 10.1016/j.sbi.2018.08.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 05/18/2018] [Accepted: 08/29/2018] [Indexed: 02/06/2023]
Abstract
The need for bacteria to interact with their environment has driven the evolution of elaborate secretion systems. By virtue of their function, secretion systems are macromolecular complexes associated with the cell envelope and therefore inherently difficult to study by conventional structural biology techniques. Cryo-electron microscopy (cryoEM) has become an invaluable technique to study large membrane-embedded complexes and led to major advances in the mechanistic understanding of secretion systems. CryoEM comprises of two main modalities, namely single particle analysis and tomography. Here, we review how detailed structures retrieved by single particle analysis combine elegantly with tomography experiments in which the secretion systems are observed in their native cellular context.
Collapse
Affiliation(s)
- Romain Kooger
- Institute of Molecular Biology & Biophysics, Eidgenössische Technische Hochschule Zürich, CH-8093 Zürich, Switzerland
| | - Piotr Szwedziak
- Institute of Molecular Biology & Biophysics, Eidgenössische Technische Hochschule Zürich, CH-8093 Zürich, Switzerland
| | - Désirée Böck
- Institute of Molecular Biology & Biophysics, Eidgenössische Technische Hochschule Zürich, CH-8093 Zürich, Switzerland
| | - Martin Pilhofer
- Institute of Molecular Biology & Biophysics, Eidgenössische Technische Hochschule Zürich, CH-8093 Zürich, Switzerland.
| |
Collapse
|
31
|
Type II Secretion-Dependent Aminopeptidase LapA and Acyltransferase PlaC Are Redundant for Nutrient Acquisition during Legionella pneumophila Intracellular Infection of Amoebas. mBio 2018; 9:mBio.00528-18. [PMID: 29666285 PMCID: PMC5904407 DOI: 10.1128/mbio.00528-18] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Legionella pneumophila genes encoding LapA, LapB, and PlaC were identified as the most highly upregulated type II secretion (T2S) genes during infection of Acanthamoeba castellanii, although these genes had been considered dispensable on the basis of the behavior of mutants lacking either lapA and lapB or plaC A plaC mutant showed even higher levels of lapA and lapB transcripts, and a lapA lapB mutant showed heightening of plaC mRNA levels, suggesting that the role of the LapA/B aminopeptidase is compensatory with respect to that of the PlaC acyltransferase. Hence, we made double mutants and found that lapA plaC mutants have an ~50-fold defect during infection of A. castellanii These data revealed, for the first time, the importance of LapA in any sort of infection; thus, we purified LapA and defined its crystal structure, activation by another T2S-dependent protease (ProA), and broad substrate specificity. When the amoebal infection medium was supplemented with amino acids, the defect of the lapA plaC mutant was reversed, implying that LapA generates amino acids for nutrition. Since the LapA and PlaC data did not fully explain the role of T2S in infection, we identified, via proteomic analysis, a novel secreted protein (NttD) that promotes infection of A. castellanii A lapA plaC nttD mutant displayed an even greater (100-fold) defect, demonstrating that the LapA, PlaC, and NttD data explain, to a significant degree, the importance of T2S. LapA-, PlaC-, and NttD-like proteins had distinct distribution patterns within and outside the Legionella genus. LapA was notable for having as its closest homologue an A. castellanii protein.IMPORTANCE Transmission of L. pneumophila to humans is facilitated by its ability to grow in Acanthamoeba species. We previously documented that type II secretion (T2S) promotes L. pneumophila infection of A. castellanii Utilizing transcriptional analysis and proteomics, double and triple mutants, and crystal structures, we defined three secreted substrates/effectors that largely clarify the role of T2S during infection of A. castellanii Particularly interesting are the unique functional overlap between an acyltransferase (PlaC) and aminopeptidase (LapA), the broad substrate specificity and eukaryotic-protein-like character of LapA, and the novelty of NttD. Linking LapA to amino acid acquisition, we defined, for the first time, the importance of secreted aminopeptidases in intracellular infection. Bioinformatic investigation, not previously applied to T2S, revealed that effectors originate from diverse sources and distribute within the Legionella genus in unique ways. The results of this study represent a major advance in understanding Legionella ecology and pathogenesis, bacterial secretion, and the evolution of intracellular parasitism.
Collapse
|
32
|
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.
Collapse
|
33
|
Guo L, Huang L, Su Y, Qin Y, Zhao L, Yan Q. secA, secD, secF, yajC, and yidC contribute to the adhesion regulation of Vibrio alginolyticus. Microbiologyopen 2017; 7:e00551. [PMID: 29057613 PMCID: PMC5911994 DOI: 10.1002/mbo3.551] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Revised: 08/26/2017] [Accepted: 09/18/2017] [Indexed: 11/30/2022] Open
Abstract
Vibrio alginolyticus caused great losses to aquaculture. Adhesion is an important virulence factor of V. alginolyticus. In this study, the relationship between V. alginolyticus adhesion and type II secretion system genes (secA, secD, secF, yajC, and yidC) was determined using gene silencing, qRT‐PCR and in vitro adhesion assay. The results showed that the expression of target genes and the bacterial adhesion exhibited significant decreases after transient gene silencing and stable gene silencing, which indicated that secA, secD, secF, yajC, and yidC played roles in the bacterial adhesion of V. alginolyticus. The expression of secA, secD, secF, yajC, and yidC were significantly influenced by temperature, salinity, pH and starvation. The results indicated that the expression of secA, secD, secF, yajC, and yidC were sensitive to different environmental factors, whereas environmental factors can affect V. alginolyticus adhesion via the expression of secA, secD, secF, yajC, and yidC.
Collapse
Affiliation(s)
- Lina Guo
- Fisheries College, Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture, Jimei University, Xiamen, Fujian, China
| | - Lixing Huang
- Fisheries College, Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture, Jimei University, Xiamen, Fujian, China
| | - Yongquan Su
- State Key Laboratory of Large Yellow Croaker Breeding, Ningde, Fujian, China.,College of Ocean & Earth Sciences, Xiamen University, Xiamen, Fujian, China
| | - Yingxue Qin
- Fisheries College, Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture, Jimei University, Xiamen, Fujian, China
| | - Lingmin Zhao
- Fisheries College, Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture, Jimei University, Xiamen, Fujian, China
| | - Qingpi Yan
- Fisheries College, Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture, Jimei University, Xiamen, Fujian, China.,State Key Laboratory of Large Yellow Croaker Breeding, Ningde, Fujian, China
| |
Collapse
|
34
|
Structural Basis of Type 2 Secretion System Engagement between the Inner and Outer Bacterial Membranes. mBio 2017; 8:mBio.01344-17. [PMID: 29042496 PMCID: PMC5646249 DOI: 10.1128/mbio.01344-17] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sophisticated nanomachines are used by bacteria for protein secretion. In Gram-negative bacteria, the type 2 secretion system (T2SS) is composed of a pseudopilus assembly platform in the inner membrane and a secretin complex in the outer membrane. The engagement of these two megadalton-sized complexes is required in order to secrete toxins, effectors, and hydrolytic enzymes. Pseudomonas aeruginosa has at least two T2SSs, with the ancestral nanomachine having a secretin complex composed of XcpQ. Until now, no high-resolution structural information was available to distinguish the features of this Pseudomonas-type secretin, which varies greatly in sequence from the well-characterized Klebsiella-type and Vibrio-type secretins. We have purified the ~1-MDa secretin complex and analyzed it by cryo-electron microscopy. Structural comparisons with the Klebsiella-type secretin complex revealed a striking structural homology despite the differences in their sequence characteristics. At 3.6-Å resolution, the secretin complex was found to have 15-fold symmetry throughout the membrane-embedded region and through most of the domains in the periplasm. However, the N1 domain and N0 domain were not well ordered into this 15-fold symmetry. We suggest a model wherein this disordering of the subunit symmetry for the periplasmic N domains provides a means to engage with the 6-fold symmetry in the inner membrane platform, with a metastable engagement that can be disrupted by substrate proteins binding to the region between XcpP, in the assembly platform, and the XcpQ secretin. How the outer membrane and inner membrane components of the T2SS engage each other and yet can allow for substrate uptake into the secretin chamber has challenged the protein transport field for some time. This vexing question is of significance because the T2SS collects folded protein substrates in the periplasm for transport out of the bacterium and yet must discriminate these few substrate proteins from all the other hundred or so folded proteins in the periplasm. The structural analysis here supports a model wherein substrates must compete against a metastable interaction between XcpP in the assembly platform and the XcpQ secretin, wherein only structurally encoded features in the T2SS substrates compete well enough to disrupt XcpQ-XcpP for entry into the XcpQ chamber, for secretion across the outer membrane.
Collapse
|
35
|
Structure of the calcium-dependent type 2 secretion pseudopilus. Nat Microbiol 2017; 2:1686-1695. [PMID: 28993624 PMCID: PMC5705324 DOI: 10.1038/s41564-017-0041-2] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 09/11/2017] [Indexed: 11/08/2022]
Abstract
Many Gram-negative bacteria use type 2 secretion systems (T2SS) to secrete proteins involved in virulence and adaptation. Transport of folded proteins via T2SS nanomachines requires the assembly of inner membrane-anchored fibers called pseudopili. Although efficient pseudopilus assembly is essential for protein secretion, structure-based functional analyses are required to unravel the mechanistic link between these processes. Here, we report an atomic model for a T2SS pseudopilus from Klebsiella oxytoca, obtained by fitting the NMR structure of its calcium-bound subunit PulG into the ~ 5 Å resolution cryo-electron microscopy (cryoEM) reconstruction of assembled fibers. This structure reveals the comprehensive network of inter-subunit contacts and unexpected features, including a disordered central region of the PulG helical stem, and highly flexible C-terminal residues on the fiber surface. NMR, mutagenesis and functional analyses highlight the key role of calcium in PulG folding and stability. Fiber disassembly in the absence of calcium provides a basis for pseudopilus length control, essential for protein secretion, and supports the Archimedes' screw model for T2S mechanism.
Collapse
|
36
|
Waack U, Johnson TL, Chedid K, Xi C, Simmons LA, Mobley HLT, Sandkvist M. Targeting the Type II Secretion System: Development, Optimization, and Validation of a High-Throughput Screen for the Identification of Small Molecule Inhibitors. Front Cell Infect Microbiol 2017; 7:380. [PMID: 28894700 PMCID: PMC5581314 DOI: 10.3389/fcimb.2017.00380] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 08/09/2017] [Indexed: 12/26/2022] Open
Abstract
Nosocomial pathogens that develop multidrug resistance present an increasing problem for healthcare facilities. Due to its rapid rise in antibiotic resistance, Acinetobacter baumannii is one of the most concerning gram-negative species. A. baumannii typically infects immune compromised individuals resulting in a variety of outcomes, including pneumonia and bacteremia. Using a murine model for bacteremia, we have previously shown that the type II secretion system (T2SS) contributes to in vivo fitness of A. baumannii. Here, we provide support for a role of the T2SS in protecting A. baumannii from human complement as deletion of the T2SS gene gspD resulted in a 100-fold reduction in surviving cells when incubated with human serum. This effect was abrogated in the absence of Factor B, a component of the alternative pathway of complement activation, indicating that the T2SS protects A. baumannii against the alternative complement pathway. Because inactivation of the T2SS results in loss of secretion of multiple enzymes, reduced in vivo fitness, and increased sensitivity to human complement, the T2SS may be a suitable target for therapeutic intervention. Accordingly, we developed and optimized a whole-cell high-throughput screening (HTS) assay based on secreted lipase activity to identify small molecule inhibitors of the T2SS. We tested the reproducibility of our assay using a 6,400-compound library. With small variation within controls and a dynamic range between positive and negative controls, the assay had a z-factor of 0.65, establishing its suitability for HTS. Our screen identified the lipase inhibitors Orlistat and Ebelactone B demonstrating the specificity of the assay. To eliminate inhibitors of lipase activity and lipase expression, two counter assays were developed and optimized. By implementing these assays, all seven tricyclic antidepressants present in the library were found to be inhibitors of the lipase, highlighting the potential of identifying alternative targets for approved pharmaceuticals. Although no T2SS inhibitor was identified among the compounds that reduced lipase activity by ≥30%, our small proof-of-concept pilot study indicates that the HTS regimen is simple, reproducible, and specific and that it can be used to screen larger libraries for the identification of T2SS inhibitors that may be developed into novel A. baumannii therapeutics.
Collapse
Affiliation(s)
- Ursula Waack
- Department of Microbiology and Immunology, University of Michigan Medical SchoolAnn Arbor, MI, United States
| | - Tanya L Johnson
- Department of Microbiology and Immunology, University of Michigan Medical SchoolAnn Arbor, MI, United States.,Department of Chemistry, Eastern Michigan UniversityYpsilanti, MI, United States
| | - Khalil Chedid
- Department of Microbiology and Immunology, University of Michigan Medical SchoolAnn Arbor, MI, United States
| | - Chuanwu Xi
- Department of Environmental Health Sciences, University of Michigan School of Public HealthAnn Arbor, MI, United States
| | - Lyle A Simmons
- Department of Molecular, Cellular, and Developmental Biology, University of MichiganAnn Arbor, MI, United States
| | - Harry L T Mobley
- Department of Microbiology and Immunology, University of Michigan Medical SchoolAnn Arbor, MI, United States
| | - Maria Sandkvist
- Department of Microbiology and Immunology, University of Michigan Medical SchoolAnn Arbor, MI, United States
| |
Collapse
|