1
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Seabaugh JA, Anderson DM. Pathogenicity and virulence of Yersinia. Virulence 2024; 15:2316439. [PMID: 38389313 PMCID: PMC10896167 DOI: 10.1080/21505594.2024.2316439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Accepted: 02/04/2024] [Indexed: 02/24/2024] Open
Abstract
The genus Yersinia includes human, animal, insect, and plant pathogens as well as many symbionts and harmless bacteria. Within this genus are Yersinia enterocolitica and the Yersinia pseudotuberculosis complex, with four human pathogenic species that are highly related at the genomic level including the causative agent of plague, Yersinia pestis. Extensive laboratory, field work, and clinical research have been conducted to understand the underlying pathogenesis and zoonotic transmission of these pathogens. There are presently more than 500 whole genome sequences from which an evolutionary footprint can be developed that details shared and unique virulence properties. Whereas the virulence of Y. pestis now seems in apparent homoeostasis within its flea transmission cycle, substantial evolutionary changes that affect transmission and disease severity continue to ndergo apparent selective pressure within the other Yersiniae that cause intestinal diseases. In this review, we will summarize the present understanding of the virulence and pathogenesis of Yersinia, highlighting shared mechanisms of virulence and the differences that determine the infection niche and disease severity.
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Affiliation(s)
- Jarett A. Seabaugh
- Department of Veterinary Pathobiology, University of Missouri, Columbia, USA
| | - Deborah M. Anderson
- Department of Veterinary Pathobiology, University of Missouri, Columbia, USA
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2
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Malik A, Kamli MR, Sabir JSM, Rather IA, Phan LT, Kim CB, Manavalan B. APLpred: A machine learning-based tool for accurate prediction and characterization of asparagine peptide lyases using sequence-derived optimal features. Methods 2024; 229:133-146. [PMID: 38944134 DOI: 10.1016/j.ymeth.2024.05.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2024] [Revised: 05/08/2024] [Accepted: 05/19/2024] [Indexed: 07/01/2024] Open
Abstract
Asparagine peptide lyase (APL) is among the seven groups of proteases, also known as proteolytic enzymes, which are classified according to their catalytic residue. APLs are synthesized as precursors or propeptides that undergo self-cleavage through autoproteolytic reaction. At present, APLs are grouped into 10 families belonging to six different clans of proteases. Recognizing their critical roles in many biological processes including virus maturation, and virulence, accurate identification and characterization of APLs is indispensable. Experimental identification and characterization of APLs is laborious and time-consuming. Here, we developed APLpred, a novel support vector machine (SVM) based predictor that can predict APLs from the primary sequences. APLpred was developed using Boruta-based optimal features derived from seven encodings and subsequently trained using five machine learning algorithms. After evaluating each model on an independent dataset, we selected APLpred (an SVM-based model) due to its consistent performance during cross-validation and independent evaluation. We anticipate APLpred will be an effective tool for identifying APLs. This could aid in designing inhibitors against these enzymes and exploring their functions. The APLpred web server is freely available at https://procarb.org/APLpred/.
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Affiliation(s)
- Adeel Malik
- Institute of Intelligence Informatics Technology, Sangmyung University, Seoul 03016, Republic of Korea
| | - Majid Rasool Kamli
- Department of Biological Sciences, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia
| | - Jamal S M Sabir
- Department of Biological Sciences, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia; Center of Excellence in Bionanoscience Research, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
| | - Irfan A Rather
- Department of Biological Sciences, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia; Center of Excellence in Bionanoscience Research, King Abdulaziz University, Jeddah 21589, Saudi Arabia
| | - Le Thi Phan
- Computational Biology and Bioinformatics Laboratory, Department of Integrative Biotechnology, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon 16419, Gyeonggi-do, Republic of Korea
| | - Chang-Bae Kim
- Department of Biotechnology, Sangmyung University, Seoul 03016, Republic of Korea.
| | - Balachandran Manavalan
- Computational Biology and Bioinformatics Laboratory, Department of Integrative Biotechnology, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon 16419, Gyeonggi-do, Republic of Korea.
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3
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Gurung JM, Amer AAA, Chen S, Diepold A, Francis MS. Type III secretion by Yersinia pseudotuberculosis is reliant upon an authentic N-terminal YscX secretor domain. Mol Microbiol 2022; 117:886-906. [PMID: 35043994 PMCID: PMC9303273 DOI: 10.1111/mmi.14880] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 01/04/2022] [Accepted: 01/11/2022] [Indexed: 11/29/2022]
Abstract
YscX was discovered as an essential part of the Yersinia type III secretion system about 20 years ago. It is required for substrate secretion and is exported itself. Despite this central role, its precise function and mode of action remains unknown. In order to address this knowledge gap, this present study refocused attention on YscX to build on the recent advances in the understanding of YscX function. Our experiments identified a N-terminal secretion domain in YscX promoting its secretion, with the first five codons constituting a minimal signal capable of promoting secretion of the signalless β-lactamase reporter. Replacing the extreme YscX N-terminus with known secretion signals of other Ysc-Yop substrates revealed that the YscX N-terminal segment contains non-redundant information needed for YscX function. Further, both in cis deletion of the YscX N-terminus in the virulence plasmid and ectopic expression of epitope tagged YscX variants again lead to stable YscX production but not type III secretion of Yop effector proteins. Mislocalisation of the needle components, SctI and SctF, accompanied this general defect in Yops secretion. Hence, a coupling exists between YscX secretion permissiveness and the assembly of an operational secretion system.
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Affiliation(s)
- Jyoti M Gurung
- Department of Molecular Biology, Umeå University, Umeå, Sweden.,Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Ayad A A Amer
- Department of Molecular Biology, Umeå University, Umeå, Sweden.,Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Shiyun Chen
- Wuhan Institute of Virology, The Chinese Academy of Sciences, Wuhan, China
| | - Andreas Diepold
- Max Planck Institute for Terrestrial Microbiology, Department of Ecophysiology, Marburg, Germany
| | - Matthew S Francis
- Department of Molecular Biology, Umeå University, Umeå, Sweden.,Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
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4
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Abstract
Type III protein secretion systems (T3SSs), or injectisomes, are multiprotein nanomachines present in many Gram-negative bacteria that have a sustained long-standing close relationship with a eukaryotic host. These secretion systems have evolved to modulate host cellular functions through the activity of the effector proteins they deliver. To reach their destination, T3SS effectors must cross the multibarrier bacterial envelope and the eukaryotic cell membrane. Passage through the bacterial envelope is mediated by the needle complex, a central component of T3SSs that expands both the inner and outer membranes of Gram-negative bacteria. A set of T3SS secreted proteins, known as translocators, form a channel in the eukaryotic plasma membrane through which the effector proteins are delivered to reach the host cell cytosol. While the effector proteins are tailored to the specific lifestyle of the bacterium that encodes them, the injectisome is conserved among the different T3SSs. The central role of T3SSs in pathogenesis and their high degree of conservation make them a desirable target for the development of antimicrobial therapies against several important bacterial pathogens.
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5
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Cao SY, Liu WB, Tan YF, Yang HY, Zhang TT, Wang T, Wang XY, Song YJ, Yang RF, Du ZM. An Interaction between the Inner Rod Protein YscI and the Needle Protein YscF Is Required to Assemble the Needle Structure of the Yersinia Type Three Secretion System. J Biol Chem 2017; 292:5488-5498. [PMID: 28196868 DOI: 10.1074/jbc.m116.743591] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 02/09/2017] [Indexed: 11/06/2022] Open
Abstract
The type III secretion system is a highly conserved virulence mechanism that is widely distributed in Gram-negative bacteria. It has a syringe-like structure composed of a multi-ring basal body that spans the bacterial envelope and a projecting needle that delivers virulence effectors into host cells. Here, we showed that the Yersinia inner rod protein YscI directly interacts with the needle protein YscF inside the bacterial cells and that this interaction depends on amino acid residues 83-102 in the carboxyl terminus of YscI. Alanine substitution of Trp-85 or Ser-86 abrogated the binding of YscI to YscF as well as needle assembly and the secretion of effectors (Yops) and the needle tip protein LcrV. However, yscI null mutants that were trans-complemented with YscI mutants that bind YscF still assembled the needle and secreted Yops, demonstrating that a direct interaction between YscF and YscI is critical for these processes. Consistently, YscI mutants that did not bind YscF resulted in greatly decreased HeLa cell cytotoxicity. Together, these results show that YscI participates in needle assembly by directly interacting with YscF.
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Affiliation(s)
- Shi-Yang Cao
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Wan-Bin Liu
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Ya-Fang Tan
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Hui-Ying Yang
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Ting-Ting Zhang
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Tong Wang
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Xiao-Yi Wang
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Ya-Jun Song
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Rui-Fu Yang
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Zong-Min Du
- From the State Key laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
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Francis MS, Amer AAA, Milton DL, Costa TRD. Site-Directed Mutagenesis and Its Application in Studying the Interactions of T3S Components. Methods Mol Biol 2017; 1531:11-31. [PMID: 27837478 DOI: 10.1007/978-1-4939-6649-3_2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Type III secretion systems are a prolific virulence determinant among Gram-negative bacteria. They are used to paralyze the host cell, which enables bacterial pathogens to establish often fatal infections-unless an effective therapeutic intervention is available. However, as a result of a catastrophic rise in infectious bacteria resistant to conventional antibiotics, these bacteria are again a leading cause of worldwide mortality. Hence, this report describes a pDM4-based site-directed mutagenesis strategy that is assisting in our foremost objective to better understand the fundamental workings of the T3SS, using Yersinia as a model pathogenic bacterium. Examples are given that clearly document how pDM4-mediated site-directed mutagenesis has been used to establish clean point mutations and in-frame deletion mutations that have been instrumental in identifying and understanding the molecular interactions between components of the Yersinia type III secretion system.
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Affiliation(s)
- Matthew S Francis
- Department of Molecular Biology, Umeå University, 6K och 6L, Sjukhusområdet, Umeå, 901 87, Sweden.
- Umeå Centre for Microbial Research, Umeå University, 6K och 6L, Sjukhusområdet, Umeå, 901 87, Sweden.
| | - Ayad A A Amer
- Department of Molecular Biology, Umeå University, 6K och 6L, Sjukhusområdet, Umeå, 901 87, Sweden
- Umeå Centre for Microbial Research, Umeå University, 6K och 6L, Sjukhusområdet, Umeå, 901 87, Sweden
- Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Debra L Milton
- Department of Molecular Biology, Umeå University, 6K och 6L, Sjukhusområdet, Umeå, 901 87, Sweden
- Umeå Centre for Microbial Research, Umeå University, 6K och 6L, Sjukhusområdet, Umeå, 901 87, Sweden
- Department of Biological and Environmental Sciences, Troy University, Troy, AL, USA
| | - Tiago R D Costa
- Department of Molecular Biology, Umeå University, 6K och 6L, Sjukhusområdet, Umeå, 901 87, Sweden
- Umeå Centre for Microbial Research, Umeå University, 6K och 6L, Sjukhusområdet, Umeå, 901 87, Sweden
- Institute of Structural and Molecular Biology, University College London and Birkbeck, Malet Street, London, UK
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7
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Ho O, Rogne P, Edgren T, Wolf-Watz H, Login FH, Wolf-Watz M. Characterization of the Ruler Protein Interaction Interface on the Substrate Specificity Switch Protein in the Yersinia Type III Secretion System. J Biol Chem 2016; 292:3299-3311. [PMID: 28039361 DOI: 10.1074/jbc.m116.770255] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 12/29/2016] [Indexed: 12/29/2022] Open
Abstract
Many pathogenic Gram-negative bacteria use the type III secretion system (T3SS) to deliver effector proteins into eukaryotic host cells. In Yersinia, the switch to secretion of effector proteins is induced first after intimate contact between the bacterium and its eukaryotic target cell has been established, and the T3SS proteins YscP and YscU play a central role in this process. Here we identify the molecular details of the YscP binding site on YscU by means of nuclear magnetic resonance (NMR) spectroscopy. The binding interface is centered on the C-terminal domain of YscU. Disrupting the YscU-YscP interaction by introducing point mutations at the interaction interface significantly reduced the secretion of effector proteins and HeLa cell cytotoxicity. Interestingly, the binding of YscP to the slowly self-cleaving YscU variant P264A conferred significant protection against autoproteolysis. The YscP-mediated inhibition of YscU autoproteolysis suggests that the cleavage event may act as a timing switch in the regulation of early versus late T3SS substrates. We also show that YscUC binds to the inner rod protein YscI with a dissociation constant (Kd ) of 3.8 μm and with 1:1 stoichiometry. The significant similarity among different members of the YscU, YscP, and YscI families suggests that the protein-protein interactions discussed in this study are also relevant for other T3SS-containing Gram-negative bacteria.
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Affiliation(s)
- Oanh Ho
- Department of Chemistry, Chemical Biological Centre
| | - Per Rogne
- Department of Chemistry, Chemical Biological Centre
| | - Tomas Edgren
- Department of Molecular Biology and The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, S-901 87 Umeå, Sweden
| | - Hans Wolf-Watz
- Department of Molecular Biology and The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, S-901 87 Umeå, Sweden
| | - Frédéric H Login
- Department of Molecular Biology and The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, S-901 87 Umeå, Sweden.
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8
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Gaytán MO, Martínez-Santos VI, Soto E, González-Pedrajo B. Type Three Secretion System in Attaching and Effacing Pathogens. Front Cell Infect Microbiol 2016; 6:129. [PMID: 27818950 PMCID: PMC5073101 DOI: 10.3389/fcimb.2016.00129] [Citation(s) in RCA: 117] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 09/27/2016] [Indexed: 02/06/2023] Open
Abstract
Enteropathogenic Escherichia coli and enterohemorrhagic E. coli are diarrheagenic bacterial human pathogens that cause severe gastroenteritis. These enteric pathotypes, together with the mouse pathogen Citrobacter rodentium, belong to the family of attaching and effacing pathogens that form a distinctive histological lesion in the intestinal epithelium. The virulence of these bacteria depends on a type III secretion system (T3SS), which mediates the translocation of effector proteins from the bacterial cytosol into the infected cells. The core architecture of the T3SS consists of a multi-ring basal body embedded in the bacterial membranes, a periplasmic inner rod, a transmembrane export apparatus in the inner membrane, and cytosolic components including an ATPase complex and the C-ring. In addition, two distinct hollow appendages are assembled on the extracellular face of the basal body creating a channel for protein secretion: an approximately 23 nm needle, and a filament that extends up to 600 nm. This filamentous structure allows these pathogens to get through the host cells mucus barrier. Upon contact with the target cell, a translocation pore is assembled in the host membrane through which the effector proteins are injected. Assembly of the T3SS is strictly regulated to ensure proper timing of substrate secretion. The different type III substrates coexist in the bacterial cytoplasm, and their hierarchical secretion is determined by specialized chaperones in coordination with two molecular switches and the so-called sorting platform. In this review, we present recent advances in the understanding of the T3SS in attaching and effacing pathogens.
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Affiliation(s)
- Meztlli O Gaytán
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México Ciudad de México, Mexico
| | - Verónica I Martínez-Santos
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México Ciudad de México, Mexico
| | - Eduardo Soto
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México Ciudad de México, Mexico
| | - Bertha González-Pedrajo
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México Ciudad de México, Mexico
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9
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Ferrell JC, Fields KA. A working model for the type III secretion mechanism in Chlamydia. Microbes Infect 2015; 18:84-92. [PMID: 26515030 DOI: 10.1016/j.micinf.2015.10.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 10/19/2015] [Accepted: 10/19/2015] [Indexed: 01/09/2023]
Abstract
It has been appreciated for almost 20 years that members of the Chlamydiales possess a virulence-associated type III secretion mechanism. Given the obligate intracellular nature of these bacteria, defining exactly how type III secretion functions to promote pathogenesis has been challenging. We present a working model herein that is based on current evidence.
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Affiliation(s)
- Joshua C Ferrell
- Department of Microbiology, Immunology & Molecular Genetics, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Kenneth A Fields
- Department of Microbiology, Immunology & Molecular Genetics, University of Kentucky College of Medicine, Lexington, KY 40536, USA.
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10
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Role of autocleavage in the function of a type III secretion specificity switch protein in Salmonella enterica serovar Typhimurium. mBio 2015; 6:e01459-15. [PMID: 26463164 PMCID: PMC4620466 DOI: 10.1128/mbio.01459-15] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Type III secretion systems (T3SSs) are multiprotein machines employed by many Gram-negative bacteria to inject bacterial effector proteins into eukaryotic host cells to promote bacterial survival and colonization. The core unit of T3SSs is the needle complex, a supramolecular structure that mediates the passage of the secreted proteins through the bacterial envelope. A distinct feature of the T3SS is that protein export occurs in a strictly hierarchical manner in which proteins destined to form the needle complex filament and associated structures are secreted first, followed by the secretion of effectors and the proteins that will facilitate their translocation through the target host cell membrane. The secretion hierarchy is established by complex mechanisms that involve several T3SS-associated components, including the “switch protein,” a highly conserved, inner membrane protease that undergoes autocatalytic cleavage. It has been proposed that the autocleavage of the switch protein is the trigger for substrate switching. We show here that autocleavage of the Salmonella enterica serovar Typhimurium switch protein SpaS is an unregulated process that occurs after its folding and before its incorporation into the needle complex. Needle complexes assembled with a precleaved form of SpaS function in a manner indistinguishable from that of the wild-type form. Furthermore, an engineered mutant of SpaS that is processed by an external protease also displays wild-type function. These results demonstrate that the cleavage event per se does not provide a signal for substrate switching but support the hypothesis that cleavage allows the proper conformation of SpaS to render it competent for its switching function. Bacterial interaction with eukaryotic hosts often involves complex molecular machines for targeted delivery of bacterial effector proteins. One such machine, the type III secretion system of some Gram-negative bacteria, serves to inject a multitude of structurally diverse bacterial proteins into the host cell. Critical to the function of these systems is their ability to secrete proteins in a strict hierarchical order, but it is unclear how the mechanism of switching works. Central to the switching mechanism is a highly conserved inner membrane protease that undergoes autocatalytic cleavage. Although it has been suggested previously that the autocleavage event is the trigger for substrate switching, we show here that this is not the case. Rather, our results show that cleavage allows the proper conformation of the protein to render it competent for its switching function. These findings may help develop inhibitors of type III secretion machines that offer novel therapeutic avenues to treat various infectious diseases.
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Login FH, Wolf-Watz H. YscU/FlhB of Yersinia pseudotuberculosis Harbors a C-terminal Type III Secretion Signal. J Biol Chem 2015; 290:26282-91. [PMID: 26338709 DOI: 10.1074/jbc.m114.633677] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Indexed: 12/20/2022] Open
Abstract
All type III secretion systems (T3SS) harbor a member of the YscU/FlhB family of proteins that is characterized by an auto-proteolytic process that occurs at a conserved cytoplasmic NPTH motif. We have previously demonstrated that YscUCC, the C-terminal peptide generated by auto-proteolysis of Yersinia pseudotuberculosis YscU, is secreted by the T3SS when bacteria are grown in Ca(2+)-depleted medium at 37 °C. Here, we investigated the secretion of this early T3S-substrate and showed that YscUCC encompasses a specific C-terminal T3S signal within the 15 last residues (U15). U15 promoted C-terminal secretion of reporter proteins like GST and YopE lacking its native secretion signal. Similar to the "classical" N-terminal secretion signal, U15 interacted with the ATPase YscN. Although U15 is critical for YscUCC secretion, deletion of the C-terminal secretion signal of YscUCC did neither affect Yop secretion nor Yop translocation. However, these deletions resulted in increased secretion of YscF, the needle subunit. Thus, these results suggest that YscU via its C-terminal secretion signal is involved in regulation of the YscF secretion.
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Affiliation(s)
- Frédéric H Login
- From the Department of Molecular Biology and The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, SE-901 87 Umeå, Sweden
| | - Hans Wolf-Watz
- From the Department of Molecular Biology and The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå Centre for Microbial Research (UCMR), Umeå University, SE-901 87 Umeå, Sweden
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12
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Negatively charged lipid membranes promote a disorder-order transition in the Yersinia YscU protein. Biophys J 2015; 107:1950-1961. [PMID: 25418176 DOI: 10.1016/j.bpj.2014.09.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 09/05/2014] [Accepted: 09/09/2014] [Indexed: 01/18/2023] Open
Abstract
The inner membrane of Gram-negative bacteria is negatively charged, rendering positively charged cytoplasmic proteins in close proximity likely candidates for protein-membrane interactions. YscU is a Yersinia pseudotuberculosis type III secretion system protein crucial for bacterial pathogenesis. The protein contains a highly conserved positively charged linker sequence that separates membrane-spanning and cytoplasmic (YscUC) domains. Although disordered in solution, inspection of the primary sequence of the linker reveals that positively charged residues are separated with a typical helical periodicity. Here, we demonstrate that the linker sequence of YscU undergoes a largely electrostatically driven coil-to-helix transition upon binding to negatively charged membrane interfaces. Using membrane-mimicking sodium dodecyl sulfate micelles, an NMR derived structural model reveals the induction of three helical segments in the linker. The overall linker placement in sodium dodecyl sulfate micelles was identified by NMR experiments including paramagnetic relaxation enhancements. Partitioning of individual residues agrees with their hydrophobicity and supports an interfacial positioning of the helices. Replacement of positively charged linker residues with alanine resulted in YscUC variants displaying attenuated membrane-binding affinities, suggesting that the membrane interaction depends on positive charges within the linker. In vivo experiments with bacteria expressing these YscU replacements resulted in phenotypes displaying significantly reduced effector protein secretion levels. Taken together, our data identify a previously unknown membrane-interacting surface of YscUC that, when perturbed by mutations, disrupts the function of the pathogenic machinery in Yersinia.
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13
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Diepold A, Wagner S. Assembly of the bacterial type III secretion machinery. FEMS Microbiol Rev 2014; 38:802-22. [PMID: 24484471 DOI: 10.1111/1574-6976.12061] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2013] [Revised: 01/02/2014] [Accepted: 01/13/2014] [Indexed: 11/29/2022] Open
Abstract
Many bacteria that live in contact with eukaryotic hosts, whether as symbionts or as pathogens, have evolved mechanisms that manipulate host cell behaviour to their benefit. One such mechanism, the type III secretion system, is employed by Gram-negative bacterial species to inject effector proteins into host cells. This function is reflected by the overall shape of the machinery, which resembles a molecular syringe. Despite the simplicity of the concept, the type III secretion system is one of the most complex known bacterial nanomachines, incorporating one to more than hundred copies of up to twenty different proteins into a multi-MDa transmembrane complex. The structural core of the system is the so-called needle complex that spans the bacterial cell envelope as a tripartite ring system and culminates in a needle protruding from the bacterial cell surface. Substrate targeting and translocation are accomplished by an export machinery consisting of various inner membrane embedded and cytoplasmic components. The formation of such a multimembrane-spanning machinery is an intricate task that requires precise orchestration. This review gives an overview of recent findings on the assembly of type III secretion machines, discusses quality control and recycling of the system and proposes an integrated assembly model.
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Affiliation(s)
- Andreas Diepold
- Department of Biochemistry, University of Oxford, Oxford, UK
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14
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Hausner J, Büttner D. The YscU/FlhB homologue HrcU from Xanthomonas controls type III secretion and translocation of early and late substrates. MICROBIOLOGY-SGM 2014; 160:576-588. [PMID: 24425767 DOI: 10.1099/mic.0.075176-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The majority of Gram-negative plant- and animal-pathogenic bacteria employ a type III secretion (T3S) system to deliver effector proteins to eukaryotic cells. Members of the YscU protein family are essential components of the T3S system and consist of a transmembrane and a cytoplasmic region that is autocatalytically cleaved at a conserved NPTH motif. YscU homologues interact with T3S substrate specificity switch (T3S4) proteins that alter the substrate specificity of the T3S system after assembly of the secretion apparatus. We previously showed that the YscU homologue HrcU from the plant pathogen Xanthomonas campestris pv. vesicatoria interacts with the T3S4 protein HpaC and is required for the secretion of translocon and effector proteins. In the present study, analysis of HrcU deletion, insertion and point mutant derivatives led to the identification of amino acid residues in the cytoplasmic region of HrcU (HrcUC) that control T3S and translocation of the predicted inner rod protein HrpB2, the translocon protein HrpF and the effector protein AvrBs3. Mutations in the vicinity of the NPTH motif interfered with HrcU cleavage and/or the interaction of HrcUC with HrpB2 and the T3S4 protein HpaC. However, HrcU function was not completely abolished, suggesting that HrcU cleavage is not crucial for pathogenicity and T3S. Given that mutations in HrcU differentially affected T3S and translocation of HrpB2 and effector proteins, we propose that HrcU controls the secretion of different T3S substrate classes by independent mechanisms.
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Affiliation(s)
- Jens Hausner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Weinbergweg 10, 06120 Halle (Saale), Germany
| | - Daniela Büttner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Weinbergweg 10, 06120 Halle (Saale), Germany
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Li Y, Li L, Huang L, Francis MS, Hu Y, Chen S. Yersinia Ysc-Yop type III secretion feedback inhibition is relieved through YscV-dependent recognition and secretion of LcrQ. Mol Microbiol 2013; 91:494-507. [PMID: 24344819 DOI: 10.1111/mmi.12474] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/28/2013] [Indexed: 12/29/2022]
Abstract
Human pathogenic Yersinia species share a virulence plasmid encoding the Ysc-Yop type III secretion system (T3SS). A plasmid-encoded anti-activator, LcrQ, negatively regulates the expression of this secretion system. Under inducible conditions, LcrQ is secreted outside of bacterial cells and this activates the T3SS, but the mechanism of targeting LcrQ for type III secretion remains largely unknown. In this study, we characterized the regulatory role of the export apparatus component YscV. Depletion or overexpression of YscV compromised Yop synthesis and this primarily prevented secretion of LcrQ. It followed that a lcrQ deletion reversed the repressive effects of excessive YscV. Further characterization demonstrated that the YscV residues 493-511 located within the C-terminal soluble cytoplasmic domain directly bound with LcrQ. Critically, YscV-LcrQ complex formation was a requirement for LcrQ secretion, since YscVΔ493-511 failed to secrete LcrQ. This forced a cytoplasmic accumulation of LcrQ, which predictably caused the feedback inhibition of Yops synthesis. Based on these observations, we proposed a model for the YscV-dependent secretion of LcrQ and its role in regulating Yop synthesis in Yersinia.
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Affiliation(s)
- Yunlong Li
- Center for Emerging Infectious Diseases, Wuhan Institute of Virology, The Chinese Academy of Sciences, Wuhan, 430071, China
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Amer AAA, Costa TRD, Farag SI, Avican U, Forsberg Å, Francis MS. Genetically engineered frameshifted YopN-TyeA chimeras influence type III secretion system function in Yersinia pseudotuberculosis. PLoS One 2013; 8:e77767. [PMID: 24098594 PMCID: PMC3789692 DOI: 10.1371/journal.pone.0077767] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 09/05/2013] [Indexed: 12/29/2022] Open
Abstract
Type III secretion is a tightly controlled virulence mechanism utilized by many gram negative bacteria to colonize their eukaryotic hosts. To infect their host, human pathogenic Yersinia spp. translocate protein toxins into the host cell cytosol through a preassembled Ysc-Yop type III secretion device. Several of the Ysc-Yop components are known for their roles in controlling substrate secretion and translocation. Particularly important in this role is the YopN and TyeA heterodimer. In this study, we confirm that Y. pseudotuberculosis naturally produce a 42 kDa YopN-TyeA hybrid protein as a result of a +1 frame shift near the 3 prime of yopN mRNA, as has been previously reported for the closely related Y. pestis. To assess the biological role of this YopN-TyeA hybrid in T3SS by Y. pseudotuberculosis, we used in cis site-directed mutagenesis to engineer bacteria to either produce predominately the YopN-TyeA hybrid by introducing +1 frame shifts to yopN after codon 278 or 287, or to produce only singular YopN and TyeA polypeptides by introducing yopN sequence from Y. enterocolitica, which is known not to produce the hybrid. Significantly, the engineered 42 kDa YopN-TyeA fusions were abundantly produced, stable, and were efficiently secreted by bacteria in vitro. Moreover, these bacteria could all maintain functionally competent needle structures and controlled Yops secretion in vitro. In the presence of host cells however, bacteria producing the most genetically altered hybrids (+1 frameshift after 278 codon) had diminished control of polarized Yop translocation. This corresponded to significant attenuation in competitive survival assays in orally infected mice, although not at all to the same extent as Yersinia lacking both YopN and TyeA proteins. Based on these studies with engineered polypeptides, most likely a naturally occurring YopN-TyeA hybrid protein has the potential to influence T3S control and activity when produced during Yersinia-host cell contact.
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Affiliation(s)
- Ayad A. A. Amer
- Department of Molecular Biology, Umeå University, Umeå, Sweden
- Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Tiago R. D. Costa
- Department of Molecular Biology, Umeå University, Umeå, Sweden
- Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
| | - Salah I. Farag
- Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Ummehan Avican
- Department of Molecular Biology, Umeå University, Umeå, Sweden
- Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
- Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Åke Forsberg
- Department of Molecular Biology, Umeå University, Umeå, Sweden
- Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
- Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Matthew S. Francis
- Department of Molecular Biology, Umeå University, Umeå, Sweden
- Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden
- * E-mail:
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Hartmann N, Büttner D. The inner membrane protein HrcV from Xanthomonas spp. is involved in substrate docking during type III secretion. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2013; 26:1176-1189. [PMID: 23777429 DOI: 10.1094/mpmi-01-13-0019-r] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Pathogenicity of the gram-negative plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria depends on a membrane-spanning type III secretion (T3S) system, which translocates effector proteins into eukaryotic host cells. In this study, we characterized the T3S system component HrcV, which is a member of the YscV/FlhA family of inner membrane proteins. HrcV consists of eight transmembrane helices and a cytoplasmic region (HrcVC). Mutant and protein-protein interaction studies showed that HrcVC is essential for protein function and binds to T3S substrates, including the early substrate HrpB2, the pilus protein HrpE, and effector proteins. Furthermore, HrcVC interacts with itself and with components and control proteins of the T3S apparatus. The interaction of HrcVC with HrpB2, HrpE, and T3S system components depends on amino acid residues in a conserved motif, designated flagella/hypersensitive response/invasion proteins export pore (FHIPEP), which is located in a cytoplasmic loop between transmembrane helix four and five of HrcV. Mutations in the FHIPEP motif abolish HrcV function but do not affect the interaction of HrcVC with effector proteins.
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Dewoody RS, Merritt PM, Marketon MM. Regulation of the Yersinia type III secretion system: traffic control. Front Cell Infect Microbiol 2013; 3:4. [PMID: 23390616 PMCID: PMC3565153 DOI: 10.3389/fcimb.2013.00004] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 01/16/2013] [Indexed: 01/03/2023] Open
Abstract
Yersinia species, as well as many other Gram-negative pathogens, use a type III secretion system (T3SS) to translocate effector proteins from the bacterial cytoplasm to the host cytosol. This T3SS resembles a molecular syringe, with a needle-like shaft connected to a basal body structure, which spans the inner and outer bacterial membranes. The basal body of the injectisome shares a high degree of homology with the bacterial flagellum. Extending from the T3SS basal body is the needle, which is a polymer of a single protein, YscF. The distal end of the needle serves as a platform for the assembly of a tip complex composed of LcrV. Though never directly observed, prevailing models assume that LcrV assists in the insertion of the pore-forming proteins YopB and YopD into the host cell membrane. This completes a bridge between the bacterium and host cell to provide a continuous channel through which effectors are delivered. Significant effort has gone into understanding how the T3SS is assembled, how its substrates are recognized and how substrate delivery is controlled. Arguably the latter topic is the least understood; however, recent advances have provided new insight, and therefore, this review will focus primarily on summarizing the current state of knowledge regarding the control of substrate delivery by the T3SS. Specifically, we will discuss the roles of YopK, as well as YopN and YopE, which have long been linked to regulation of translocation. We also propose models whereby the YopK regulator communicates with the basal body of the T3SS to control translocation.
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Frost S, Ho O, Login FH, Weise CF, Wolf-Watz H, Wolf-Watz M. Autoproteolysis and intramolecular dissociation of Yersinia YscU precedes secretion of its C-terminal polypeptide YscU(CC). PLoS One 2012; 7:e49349. [PMID: 23185318 PMCID: PMC3504009 DOI: 10.1371/journal.pone.0049349] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 10/08/2012] [Indexed: 01/14/2023] Open
Abstract
Type III secretion system mediated secretion and translocation of Yop-effector proteins across the eukaryotic target cell membrane by pathogenic Yersinia is highly organized and is dependent on a switching event from secretion of early structural substrates to late effector substrates (Yops). Substrate switching can be mimicked in vitro by modulating the calcium levels in the growth medium. YscU that is essential for regulation of this switch undergoes autoproteolysis at a conserved N↑PTH motif, resulting in a 10 kDa C-terminal polypeptide fragment denoted YscU(CC). Here we show that depletion of calcium induces intramolecular dissociation of YscU(CC) from YscU followed by secretion of the YscU(CC) polypeptide. Thus, YscU(CC) behaved in vivo as a Yop protein with respect to secretion properties. Further, destabilized yscU mutants displayed increased rates of dissociation of YscU(CC)in vitro resulting in enhanced Yop secretion in vivo at 30°C relative to the wild-type strain.These findings provide strong support to the relevance of YscU(CC) dissociation for Yop secretion. We propose that YscU(CC) orchestrates a block in the secretion channel that is eliminated by calcium depletion. Further, the striking homology between different members of the YscU/FlhB family suggests that this protein family possess regulatory functions also in other bacteria using comparable mechanisms.
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Affiliation(s)
- Stefan Frost
- Department of Molecular Biology and The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Oanh Ho
- Department of Chemistry, Chemical Biological Center, Umeå University, Umeå, Sweden
| | - Frédéric H. Login
- Department of Molecular Biology and The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Christoph F. Weise
- Department of Chemistry, Chemical Biological Center, Umeå University, Umeå, Sweden
| | - Hans Wolf-Watz
- Department of Molecular Biology and The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Magnus Wolf-Watz
- Department of Chemistry, Chemical Biological Center, Umeå University, Umeå, Sweden
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Protein export according to schedule: architecture, assembly, and regulation of type III secretion systems from plant- and animal-pathogenic bacteria. Microbiol Mol Biol Rev 2012; 76:262-310. [PMID: 22688814 DOI: 10.1128/mmbr.05017-11] [Citation(s) in RCA: 304] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Flagellar and translocation-associated type III secretion (T3S) systems are present in most gram-negative plant- and animal-pathogenic bacteria and are often essential for bacterial motility or pathogenicity. The architectures of the complex membrane-spanning secretion apparatuses of both systems are similar, but they are associated with different extracellular appendages, including the flagellar hook and filament or the needle/pilus structures of translocation-associated T3S systems. The needle/pilus is connected to a bacterial translocon that is inserted into the host plasma membrane and mediates the transkingdom transport of bacterial effector proteins into eukaryotic cells. During the last 3 to 5 years, significant progress has been made in the characterization of membrane-associated core components and extracellular structures of T3S systems. Furthermore, transcriptional and posttranscriptional regulators that control T3S gene expression and substrate specificity have been described. Given the architecture of the T3S system, it is assumed that extracellular components of the secretion apparatus are secreted prior to effector proteins, suggesting that there is a hierarchy in T3S. The aim of this review is to summarize our current knowledge of T3S system components and associated control proteins from both plant- and animal-pathogenic bacteria.
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Role of EscP (Orf16) in injectisome biogenesis and regulation of type III protein secretion in enteropathogenic Escherichia coli. J Bacteriol 2012; 194:6029-45. [PMID: 22923600 DOI: 10.1128/jb.01215-12] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Enteropathogenic Escherichia coli employs a type III secretion system (T3SS) to translocate virulence effector proteins directly into enterocyte host cells, leading to diarrheal disease. The T3SS is encoded within the chromosomal locus of enterocyte effacement (LEE). The function of some of the LEE-encoded proteins remains unknown. Here we investigated the role of the Orf16 protein in T3SS biogenesis and function. An orf16 deletion mutant showed translocator and effector protein secretion profiles different from those of wild-type cells. The orf16 null strain produced T3S structures with abnormally long needles and filaments that caused weak hemolysis of red blood cells. Furthermore, the number of fully assembled T3SSs was also reduced in the orf16 mutant, indicating that Orf16, though not essential, is required for efficient T3SS assembly. Analysis of protein secretion revealed that Orf16 is a T3SS-secreted substrate and regulates the secretion of the inner rod component EscI. Both pulldown and yeast two-hybrid assays showed that Orf16 interacts with the C-terminal domain of an inner membrane component of the secretion apparatus, EscU; the inner rod protein EscI; the needle protein EscF; and the multieffector chaperone CesT. These results suggest that Orf16 regulates needle length and, along with EscU, participates in a substrate specificity switch from early substrates to translocators. Taken together, our results suggest that Orf16 acts as a molecular measuring device in a way similar to that of members of the Yersinia YscP and flagellar FliK protein family. Therefore, we propose that this protein be renamed EscP.
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Shen DK, Moriya N, Martinez-Argudo I, Blocker AJ. Needle length control and the secretion substrate specificity switch are only loosely coupled in the type III secretion apparatus of Shigella. MICROBIOLOGY-SGM 2012; 158:1884-1896. [PMID: 22575894 PMCID: PMC3542141 DOI: 10.1099/mic.0.059618-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The type III secretion apparatus (T3SA), which is evolutionarily and structurally related to the bacterial flagellar hook basal body, is a key virulence factor used by many Gram-negative bacteria to inject effector proteins into host cells. A hollow extracellular needle forms the injection conduit of the T3SA. Its length is tightly controlled to match specific structures at the bacterial and host-cell surfaces but how this occurs remains incompletely understood. The needle is topped by a tip complex, which senses the host cell and inserts as a translocation pore in the host membrane when secretion is activated. The interaction of two conserved proteins, inner-membrane Spa40 and secreted Spa32, respectively, in Shigella, is proposed to regulate needle length and to flick a type III secretion substrate specificity switch from needle components/Spa32 to translocator/effector substrates. We found that, as in T3SAs from other species, substitution N257A within the conserved cytoplasmic NPTH region in Spa40 prevented its autocleavage and substrate specificity switching. Yet, the spa40N257A mutant made only slightly longer needles with a few needle tip complexes, although it could not form translocation pores. On the other hand, Δspa32, which makes extremely long needles and also formed only few tip complexes, could still form some translocation pores, indicating that it could switch substrate specificity to some extent. Therefore, loss of needle length control and defects in secretion specificity switching are not tightly coupled in either a Δspa32 mutant or a spa40N257A mutant.
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Affiliation(s)
- Da-Kang Shen
- Schools of Cellular and Molecular Medicine and Biochemistry, University of Bristol, Bristol BS8 1TD, UK
| | - Nao Moriya
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadoaka, Suita, Osaka 565-0871, Japan.,Schools of Cellular and Molecular Medicine and Biochemistry, University of Bristol, Bristol BS8 1TD, UK
| | - Isabel Martinez-Argudo
- Schools of Cellular and Molecular Medicine and Biochemistry, University of Bristol, Bristol BS8 1TD, UK
| | - Ariel J Blocker
- Schools of Cellular and Molecular Medicine and Biochemistry, University of Bristol, Bristol BS8 1TD, UK
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Impact of the N-terminal secretor domain on YopD translocator function in Yersinia pseudotuberculosis type III secretion. J Bacteriol 2011; 193:6683-700. [PMID: 21965570 DOI: 10.1128/jb.00210-11] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Type III secretion systems (T3SSs) secrete needle components, pore-forming translocators, and the translocated effectors. In part, effector recognition by a T3SS involves their N-terminal amino acids and their 5' mRNA. To investigate whether similar molecular constraints influence translocator secretion, we scrutinized this region within YopD from Yersinia pseudotuberculosis. Mutations in the 5' end of yopD that resulted in specific disruption of the mRNA sequence did not affect YopD secretion. On the other hand, a few mutations affecting the protein sequence reduced secretion. Translational reporter fusions identified the first five codons as a minimal N-terminal secretion signal and also indicated that the YopD N terminus might be important for yopD translation control. Hybrid proteins in which the N terminus of YopD was exchanged with the equivalent region of the YopE effector or the YopB translocator were also constructed. While the in vitro secretion profile was unaltered, these modified bacteria were all compromised with respect to T3SS activity in the presence of immune cells. Thus, the YopD N terminus does harbor a secretion signal that may also incorporate mechanisms of yopD translation control. This signal tolerates a high degree of variation while still maintaining secretion competence suggestive of inherent structural peculiarities that make it distinct from secretion signals of other T3SS substrates.
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Thomassin JL, He X, Thomas NA. Role of EscU auto-cleavage in promoting type III effector translocation into host cells by enteropathogenic Escherichia coli. BMC Microbiol 2011; 11:205. [PMID: 21933418 PMCID: PMC3189125 DOI: 10.1186/1471-2180-11-205] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Accepted: 09/20/2011] [Indexed: 01/13/2023] Open
Abstract
Background Type III secretion systems (T3SS) of bacterial pathogens coordinate effector protein injection into eukaryotic cells. The YscU/FlhB group of proteins comprises members associated with T3SS which undergo a specific auto-cleavage event at a conserved NPTH amino acid sequence. The crystal structure of the C-terminal portion of EscU from enteropathogenic Escherichia coli (EPEC) suggests this auto-cleaving protein provides an interface for substrate interactions involved in type III secretion events. Results We demonstrate EscU must be auto-cleaved for bacteria to efficiently deliver type III effectors into infected cells. A non-cleaving EscU(N262A) variant supported very low levels of in vitro effector secretion. These effector proteins were not able to support EPEC infection of cultured HeLa cells. In contrast, EscU(P263A) was demonstrated to be partially auto-cleaved and moderately restored effector translocation and functionality during EPEC infection, revealing an intermediate phenotype. EscU auto-cleavage was not required for inner membrane association of the T3SS ATPase EscN or the ring forming protein EscJ. In contrast, in the absence of EscU auto-cleavage, inner membrane association of the multicargo type III secretion chaperone CesT was altered suggesting that EscU auto-cleavage supports docking of chaperone-effector complexes at the inner membrane. In support of this interpretation, evidence of novel effector protein breakdown products in secretion assays were linked to the non-cleaved status of EscU(N262A). Conclusions These data provide new insight into the role of EscU auto-cleavage in EPEC. The experimental data suggests that EscU auto-cleavage results in a suitable binding interface at the inner membrane that accommodates protein complexes during type III secretion events. The results also demonstrate that altered EPEC genetic backgrounds that display intermediate levels of effector secretion and translocation can be isolated and studied. These genetic backgrounds should be valuable in deciphering sequential and temporal events involved in EPEC type III secretion.
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Affiliation(s)
- Jenny-Lee Thomassin
- Department of Microbiology and Immunology, Dalhousie University, 5850 College Street, PO Box 15000, Halifax, Nova Scotia, B3H 4R2 Canada
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Rawlings ND, Barrett AJ, Bateman A. Asparagine peptide lyases: a seventh catalytic type of proteolytic enzymes. J Biol Chem 2011; 286:38321-38328. [PMID: 21832066 PMCID: PMC3207474 DOI: 10.1074/jbc.m111.260026] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The terms “proteolytic enzyme” and “peptidase” have been treated as synonymous, and all proteolytic enzymes have been considered to be hydrolases (EC 3.4). However, the recent discovery of proteins that cleave themselves at asparagine residues indicates that not all peptide bond cleavage occurs by hydrolysis. These self-cleaving proteins include the Tsh protein precursor of Escherichia coli, in which the large C-terminal propeptide acts as an autotransporter; certain viral coat proteins; and proteins containing inteins. Proteolysis is the action of an amidine lyase (EC 4.3.2). These proteolytic enzymes are also the first in which the nucleophile is an asparagine, defining the seventh proteolytic catalytic type and the first to be discovered since 2004. We have assembled ten families based on sequence similarity in which cleavage is thought to be catalyzed by an asparagine.
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Affiliation(s)
- Neil David Rawlings
- Wellcome Trust Genome Campus, The Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire CB10 1SA, United Kingdom.
| | - Alan John Barrett
- Wellcome Trust Genome Campus, The Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire CB10 1SA, United Kingdom
| | - Alex Bateman
- Wellcome Trust Genome Campus, The Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire CB10 1SA, United Kingdom
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Schulz S, Büttner D. Functional characterization of the type III secretion substrate specificity switch protein HpaC from Xanthomonas campestris pv. vesicatoria. Infect Immun 2011; 79:2998-3011. [PMID: 21576326 PMCID: PMC3147569 DOI: 10.1128/iai.00180-11] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Accepted: 05/10/2011] [Indexed: 12/31/2022] Open
Abstract
Pathogenicity of Xanthomonas campestris pv. vesicatoria depends on a type III secretion (T3S) system which translocates effector proteins into eukaryotic cells and is associated with an extracellular pilus and a translocon in the host plasma membrane. T3S substrate specificity is controlled by the cytoplasmic switch protein HpaC, which interacts with the C-terminal domain of the inner membrane protein HrcU (HrcU(C)). HpaC promotes the secretion of translocon and effector proteins but prevents the efficient secretion of the early T3S substrate HrpB2, which is required for pilus assembly. In this study, complementation assays with serial 10-amino-acid HpaC deletion derivatives revealed that the T3S substrate specificity switch depends on N- and C-terminal regions of HpaC, whereas amino acids 42 to 101 appear to be dispensable for the contribution of HpaC to the secretion of late substrates. However, deletions in the central region of HpaC affect the secretion of HrpB2, suggesting that the mechanisms underlying HpaC-dependent control of early and late substrates can be uncoupled. The results of interaction and expression studies with HpaC deletion derivatives showed that amino acids 112 to 212 of HpaC provide the binding site for HrcU(C) and severely reduce T3S when expressed ectopically in the wild-type strain. We identified a conserved phenylalanine residue at position 175 of HpaC that is required for both protein function and the binding of HpaC to HrcU(C). Taking these findings together, we concluded that the interaction between HpaC and HrcU(C) is essential but not sufficient for T3S substrate specificity switching.
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Affiliation(s)
- Steve Schulz
- Institute of Biology, Genetics Department, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany
| | - Daniela Büttner
- Institute of Biology, Genetics Department, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany
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Osborne SE, Coombes BK. Expression and secretion hierarchy in the nonflagellar type III secretion system. Future Microbiol 2011; 6:193-202. [PMID: 21366419 DOI: 10.2217/fmb.10.172] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Type III secretion systems that deliver bacterial proteins into eukaryotic cells are the basis for both symbiotic and pathogenic relationships between many Gram-negative bacteria and their hosts. Exploration of the structure, function and assembly of this secretion system has greatly enhanced our knowledge of bacterial ecology in the context of infectious disease and has spawned new avenues in anti-infective research with a view towards inhibiting virulence functions. We outline advances in understanding type III secretion system function with specific focus on how assembly is hierarchically coordinated at the level of expression and how the type III secretion system mediates transitions in substrate specificity.
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Affiliation(s)
- Suzanne E Osborne
- Michael G DeGroote Institute for Infectious Disease Research & Department of Biochemistry & Biomedical Sciences, HSC-4H17, McMaster University, Hamilton, ON, Canada
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Chen Y, Anderson DM. Expression hierarchy in the Yersinia type III secretion system established through YopD recognition of RNA. Mol Microbiol 2011; 80:966-80. [PMID: 21481017 PMCID: PMC4128491 DOI: 10.1111/j.1365-2958.2011.07623.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The Yersinia type III secretion system (T3SS) is environmentally responsive to enable its rapid induction upon contact with host cells and is necessary for Yersiniae to establish a replicative niche and cause disease. YopD, a translocator protein, represses the expression of T3SS genes until signalled by environmental cues, a mechanism known as the low calcium response. In this work, we investigated recognition of target genes by Yersinia pestis YopD. Expression of all genes of the T3SS was induced in a yopD mutant, though not to the same degree, with effector Yops most affected. Two, short AU-rich sequence elements up- and downstream of start codons of target genes were necessary but not sufficient for YopD mediated repression. Purified YopD-LcrH bound specifically to target RNAs in vitro with different relative affinities, with effector Yops having greater affinity. Together, the data suggest YopD binds to T3SS transcripts where it may prevent ribosome binding causing accelerated mRNA degradation. This regulatory mechanism may ensure an expression hierarchy during the low calcium response as low affinity YopD targets such as chaperones would be translated prior to high affinity targets such as effector Yops allowing the bacteria another layer of control over Yop translocation during infection.
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Affiliation(s)
- Yuqing Chen
- Department of Veterinary Pathobiology, University of Missouri College of Veterinary Medicine, Columbia, MO 65211
| | - Deborah M. Anderson
- Department of Veterinary Pathobiology, University of Missouri College of Veterinary Medicine, Columbia, MO 65211
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29
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Lorenz C, Büttner D. Secretion of early and late substrates of the type III secretion system from Xanthomonas is controlled by HpaC and the C-terminal domain of HrcU. Mol Microbiol 2011; 79:447-67. [PMID: 21219463 PMCID: PMC3040844 DOI: 10.1111/j.1365-2958.2010.07461.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/05/2010] [Indexed: 11/27/2022]
Abstract
The plant pathogenic bacterium Xanthomonas campestris pv. vesicatoria utilizes a type III secretion (T3S) system to inject effector proteins into eukaryotic cells. T3S substrate specificity is controlled by HpaC, which promotes secretion of translocon and effector proteins but prevents efficient secretion of the early substrate HrpB2. HpaC and HrpB2 interact with the C-terminal domain (HrcU(C) ) of the FlhB/YscU homologue HrcU. Here, we provide experimental evidence that HrcU is proteolytically cleaved at the conserved NPTH motif, which is required for binding of both HpaC and HrpB2 to HrcU(C) . The results of mutant studies showed that cleavage of HrcU contributes to pathogenicity and secretion of late substrates but is dispensable for secretion of HrpB2, which is presumably secreted prior to HrcU cleavage. The introduction of a point mutation (Y318D) into HrcU(C) activated secretion of late substrates in the absence of HpaC and suppressed the hpaC mutant phenotype. However, secretion of HrpB2 was unaffected by HrcU(Y318D) , suggesting that the export of early and late substrates is controlled by independent mechanisms that can be uncoupled. As HrcU(Y318D) did not interact with HrpB2 and HpaC, we propose that the substrate specificity switch leads to the release of HrcU(C) -bound HrpB2 and HpaC.
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Affiliation(s)
- Christian Lorenz
- Institute of Biology, Department of Genetics, Martin-Luther University Halle-WittenbergD-06099 Halle (Saale), Germany
| | - Daniela Büttner
- Institute of Biology, Department of Genetics, Martin-Luther University Halle-WittenbergD-06099 Halle (Saale), Germany
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Botteaux A, Kayath CA, Page AL, Jouihri N, Sani M, Boekema E, Biskri L, Parsot C, Allaoui A. The 33 carboxyl-terminal residues of Spa40 orchestrate the multi-step assembly process of the type III secretion needle complex in Shigella flexneri. MICROBIOLOGY-SGM 2010; 156:2807-2817. [PMID: 20507885 DOI: 10.1099/mic.0.039651-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The type III secretion apparatus (T3SA) is a central virulence factor of many Gram-negative bacteria. Its overall morphology consists of a cytoplasmic region, inner- and outer-membrane sections and an extracellular needle. In Shigella, the length of the needle is regulated by Spa32. To understand better the role of Spa32 we searched for its interacting partners using a two-hybrid screen in yeast. We found that Spa32 interacts with the 33 C-terminal residues (CC*) of Spa40, a member of the conserved FlhB/YscU family. Using a GST pull-down assay we confirmed this interaction and identified additional interactions between Spa40 and the type III secretion components Spa33, Spa47, MxiK, MxiN and MxiA. Inactivation of spa40 abolished protein secretion and led to needleless structures. Genetic and functional analyses were used to investigate the roles of residues L310 and V320, located within the CC* domain of Spa40, in the assembly of the T3SA. Spa40 cleavage, at the conserved NPTH motif, is required for assembly of the T3SA and for its interaction with Spa32, Spa33 and Spa47. In contrast, unprocessed forms of Spa40 interacted only with MxiA, MxiK and MxiN. Our data suggest that the conformation of the cytoplasmic domain of Spa40 defines the multi-step assembly process of the T3SA.
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Affiliation(s)
- Anne Botteaux
- Laboratoire de Bactériologie Moléculaire, Faculté de Médecine, Université Libre de Bruxelles, Route de Lennik, 808, 1070 Bruxelles, Belgium
| | - Christian A Kayath
- Laboratoire de Bactériologie Moléculaire, Faculté de Médecine, Université Libre de Bruxelles, Route de Lennik, 808, 1070 Bruxelles, Belgium
| | - Anne-Laure Page
- INSERM U786, 25 rue du Dr Roux, F-75724 Paris Cedex 15, France.,Laboratoire de Pathogénie Microbienne, Institut Pasteur, 27-28 Rue du Dr Roux, 75725 Paris Cedex 15, France
| | - Nouredine Jouihri
- Laboratoire de Bactériologie Moléculaire, Faculté de Médecine, Université Libre de Bruxelles, Route de Lennik, 808, 1070 Bruxelles, Belgium
| | - Musa Sani
- Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, The Netherlands
| | - Egbert Boekema
- Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, The Netherlands
| | - Latéfa Biskri
- Laboratoire de Bactériologie Moléculaire, Faculté de Médecine, Université Libre de Bruxelles, Route de Lennik, 808, 1070 Bruxelles, Belgium
| | - Claude Parsot
- INSERM U786, 25 rue du Dr Roux, F-75724 Paris Cedex 15, France.,Laboratoire de Pathogénie Microbienne, Institut Pasteur, 27-28 Rue du Dr Roux, 75725 Paris Cedex 15, France
| | - Abdelmounaaïm Allaoui
- Laboratoire de Bactériologie Moléculaire, Faculté de Médecine, Université Libre de Bruxelles, Route de Lennik, 808, 1070 Bruxelles, Belgium
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Davis AJ, Díaz DADJ, Mecsas J. A dominant-negative needle mutant blocks type III secretion of early but not late substrates in Yersinia. Mol Microbiol 2010; 76:236-59. [PMID: 20199604 DOI: 10.1111/j.1365-2958.2010.07096.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Yersinia pseudotuberculosis uses a type III secretion system (T3SS) to deliver effectors into host cells. A key component of the T3SS is the needle, which is a hollow tube on the bacterial surface through which effectors are secreted, composed of the YscF protein. To study needle assembly, we performed a screen for dominant-negative yscF alleles that prevented effector secretion in the presence of wild-type (WT) YscF. One allele, yscF-L54V, prevents WT YscF secretion and needle assembly, although purified YscF-L54V polymerizes in vitro. YscF-L54V binds to its chaperones YscE and YscG, and the YscF-L54V-EG complex targets to the T3SS ATPase, YscN. We propose that YscF-L54V stalls at a binding site in the needle assembly pathway following its release from the chaperones, which blocks the secretion of WT YscF and other early substrates required for building a needle. Interestingly, YscF-L54V does not affect the activity of pre-assembled actively secreting machines, indicating that a factor and/or binding site required for YscF secretion is absent from T3SS machines already engaged in effector secretion. Thus, substrate switching may involve the removal of an early substrate-specific binding site as a mechanism to exclude early substrates from Yop-secreting machines.
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Affiliation(s)
- Alison J Davis
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111, USA.
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