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Dodd D, Moon YH, Swaminathan K, Mackie RI, Cann IKO. Transcriptomic analyses of xylan degradation by Prevotella bryantii and insights into energy acquisition by xylanolytic bacteroidetes. J Biol Chem 2010; 285:30261-73. [PMID: 20622018 DOI: 10.1074/jbc.m110.141788] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Enzymatic depolymerization of lignocellulose by microbes in the bovine rumen and the human colon is critical to gut health and function within the host. Prevotella bryantii B(1)4 is a rumen bacterium that efficiently degrades soluble xylan. To identify the genes harnessed by this bacterium to degrade xylan, the transcriptomes of P. bryantii cultured on either wheat arabinoxylan or a mixture of its monosaccharide components were compared by DNA microarray and RNA sequencing approaches. The most highly induced genes formed a cluster that contained putative outer membrane proteins analogous to the starch utilization system identified in the prominent human gut symbiont Bacteroides thetaiotaomicron. The arrangement of genes in the cluster was highly conserved in other xylanolytic Bacteroidetes, suggesting that the mechanism employed by xylan utilizers in this phylum is conserved. A number of genes encoding proteins with unassigned function were also induced on wheat arabinoxylan. Among these proteins, a hypothetical protein with low similarity to glycoside hydrolases was shown to possess endoxylanase activity and subsequently assigned to glycoside hydrolase family 5. The enzyme was designated PbXyn5A. Two of the most similar proteins to PbXyn5A were hypothetical proteins from human colonic Bacteroides spp., and when expressed each protein exhibited endoxylanase activity. By using site-directed mutagenesis, we identified two amino acid residues that likely serve as the catalytic acid/base and nucleophile as in other GH5 proteins. This study therefore provides insights into capture of energy by xylanolytic Bacteroidetes and the application of their enzymes as a resource in the biofuel industry.
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Affiliation(s)
- Dylan Dodd
- Department of Microbiology, University of Illinois, Urbana, Illinois 61801, USA
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52
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Hamada D, Hamaguchi M, Suzuki KN, Sakata I, Yanagihara I. Cytoskeleton-modulating effectors of enteropathogenic and enterohemorrhagic Escherichia coli: a case for EspB as an intrinsically less-ordered effector. FEBS J 2010; 277:2409-15. [PMID: 20477867 DOI: 10.1111/j.1742-4658.2010.07655.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Enterohemorrhagic and enteropathogenic Escherichia coli produce various effector proteins that are directly injected into the host-cell cytosol through the type III secretion system. E. coli secreted protein (Esp)B is one such effector protein, and affects host-cell morphology by reorganizing actin networks. Unlike most globular proteins that have well-ordered, rigid structures, the structures of type III secretion system effectors from pathogenic Gram-negative bacteria, including EspB, are often less well-ordered. This minireview focuses on the functional relationship between the structural properties of these proteins and their roles in type III secretion system-associated pathogenesis.
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Affiliation(s)
- Daizo Hamada
- Division of Structural Biology (G-COE), Department of Biochemistry and Molecular Biology, Graduate School of Medicine, Kobe University, Chuo-ku, Kobe, Japan.
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Williams TJ, Burg DW, Raftery MJ, Poljak A, Guilhaus M, Pilak O, Cavicchioli R. Global proteomic analysis of the insoluble, soluble, and supernatant fractions of the psychrophilic archaeon Methanococcoides burtonii. Part I: the effect of growth temperature. J Proteome Res 2010; 9:640-52. [PMID: 20039705 DOI: 10.1021/pr900509n] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The response of the cold-adapted (psychrophilic) methanogenic archaeon Methanococcoides burtonii to growth temperature was investigated using differential proteomics (postincorporation isobaric labeling) and tandem liquid chromatography-mass spectrometry (LC/LC-MS/MS). This is the first proteomic study of M. burtonii to include techniques that specifically enrich for both surface and membrane proteins and to assess the effects of growth temperature (4 vs 23 degrees C) and carbon source (trimethylamine vs methanol) on cellular protein levels. Numerous surface layer proteins were more abundant at 4 degrees C, indicating an extensive remodeling of the cell envelope in response to low temperature. Many of these surface proteins contain domains associated with cell adhesion. Within the cell, small proteins each composed of a single TRAM domain were recovered as important cold adaptation proteins and might serve as RNA chaperones, in an analogous manner to Csp proteins (absent from M. burtonii). Other proteins that had higher abundances at 4 degrees C can be similarly tied to relieving or resolving the adverse affects of cold growth temperature on translational capacity and correct protein folding. The proteome of M. burtonii grown at 23 degrees C was dominated by oxidative stress proteins, as well as a large number of integral membrane proteins of unknown function. This is the first truly global proteomic study of a psychrophilic archaeon and greatly expands knowledge of the cellular mechanisms underpinning cold adaptation in the Archaea.
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Affiliation(s)
- Timothy J Williams
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, 2052, NSW, Australia
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Zhou F, Chen H, Xu Y. GASdb: a large-scale and comparative exploration database of glycosyl hydrolysis systems. BMC Microbiol 2010; 10:69. [PMID: 20202206 PMCID: PMC2838879 DOI: 10.1186/1471-2180-10-69] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Accepted: 03/04/2010] [Indexed: 11/29/2022] Open
Abstract
Background The genomes of numerous cellulolytic organisms have been recently sequenced or in the pipeline of being sequenced. Analyses of these genomes as well as the recently sequenced metagenomes in a systematic manner could possibly lead to discoveries of novel biomass-degradation systems in nature. Description We have identified 4,679 and 49,099 free acting glycosyl hydrolases with or without carbohydrate binding domains, respectively, by scanning through all the proteins in the UniProt Knowledgebase and the JGI Metagenome database. Cellulosome components were observed only in bacterial genomes, and 166 cellulosome-dependent glycosyl hydrolases were identified. We observed, from our analysis data, unexpected wide distributions of two less well-studied bacterial glycosyl hydrolysis systems in which glycosyl hydrolases may bind to the cell surface directly rather than through linking to surface anchoring proteins, or cellulosome complexes may bind to the cell surface by novel mechanisms other than the other used SLH domains. In addition, we found that animal-gut metagenomes are substantially enriched with novel glycosyl hydrolases. Conclusions The identified biomass degradation systems through our large-scale search are organized into an easy-to-use database GASdb at http://csbl.bmb.uga.edu/~ffzhou/GASdb/, which should be useful to both experimental and computational biofuel researchers.
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Affiliation(s)
- Fengfeng Zhou
- Computational Systems Biology Laboratory, Department of Biochemistry and Molecular Biology, and Institute of Bioinformatics, University of Georgia, Athens, GA 30602, USA
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55
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Bayer-Giraldi M, Uhlig C, John U, Mock T, Valentin K. Antifreeze proteins in polar sea ice diatoms: diversity and gene expression in the genus Fragilariopsis. Environ Microbiol 2010; 12:1041-52. [PMID: 20105220 DOI: 10.1111/j.1462-2920.2009.02149.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Fragilariopsis is a dominating psychrophilic diatom genus in polar sea ice. The two species Fragilariopsis cylindrus and Fragilariopsis curta are able to grow and divide below freezing temperature of sea water and above average sea water salinity. Here we show that antifreeze proteins (AFPs), involved in cold adaptation in several psychrophilic organisms, are widespread in the two polar species. The presence of AFP genes (afps) as a multigene family indicated the importance of this group of genes for the genus Fragilariopsis, possibly contributing to its success in sea ice. Protein phylogeny showed the potential mobility of afps, which appear to have crossed kingdom and domain borders, occurring in Bacteria, diatoms, crustaceans and fungi. Our results revealed a broad distribution of AFPs not only in polar organisms but also in taxa apparently not related to cold environments, suggesting that these proteins may be multifunctional. The relevance of AFPs to Fragilariopsis was also shown by gene expression analysis. Under stress conditions typical for sea ice, with subzero temperatures and high salinities, F. cylindrus and F. curta strongly expressed selected afps. An E/G point mutation in the Fragilariopsis AFPs may play a role in gene expression activity and protein function.
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Immunological characterization of the subunits of type A botulinum neurotoxin and different components of its associated proteins. Toxicon 2009; 53:616-24. [PMID: 19673075 DOI: 10.1016/j.toxicon.2009.01.017] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Botulinum neurotoxins (BoNTs) constitute a family of seven structurally similar but antigenically distinct proteins produced by different strains of Clostridium botulinum. Type A botulinum neurotoxin (BoNT/A) is produced along with 6 neurotoxin associated proteins (NAPs) including hemagglutinin (Hn-33) through polycistronic expression of a clustered group of genes to form a complex (BoNT/AC). The presence of NAPs enhances the oral toxicity of the neurotoxin significantly. Hn-33 makes up the largest fraction of NAPs in BoNT/AC and strongly protects BoNT/A against proteases of the GI tract. BoNT in its complex form is also used in therapeutic and cosmetic applications to treat several neuromuscular disorders. In this study immunological reactivity of BoNT/A in its purified and complex forms, neurotoxin associated proteins, and Hn-33 have been examined using enzyme-linked immunosorbent assay (ELISA). Antibodies raised against the whole complex reacted 60 times better with the complex and 35 times better with Hn-33 and NAPs compared to the purified neurotoxin suggesting stronger immunogenicity of NAPs over that of purified neurotoxin and a higher potential of BoNT/AC and its associated proteins to induce host immune response. This observation also suggests that Hn-33 and other NAPs could potentially be employed as adjuvants for development of vaccines against botulism and could be a good surrogate for botulinum diagnostics. ELISA binding curves of BoNT/AC and BoNT/A with antibodies raised against BoNT/A indicate that BoNT/A in its purified and complex forms induces equal immunogenic response and a 2.5-fold higher immunogenic response compared to BoNT/A light and heavy chains. We have also discovered a new protein, an intimin analog, present within the complex preparation of BoNT/A which shows dramatically high immunoreactivity.
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Localization and characterization of VVA0331, a 489-kDa RTX-like protein, in Vibrio vulnificus YJ016. Arch Microbiol 2009; 191:441-50. [PMID: 19326097 DOI: 10.1007/s00203-009-0471-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Revised: 02/19/2009] [Accepted: 03/06/2009] [Indexed: 12/19/2022]
Abstract
Vibrio vulnificus YJ016 contains three genes encoding proteins homologous to repeats-in-toxin proteins. One of these genes, vva0331, possesses a long open reading frame of 13,971 bp in length and resides on the small chromosome between two gene clusters encoding a type I secretion system and several regulatory proteins, respectively. Bioinformatic analysis revealed that VVA0331 consist of nineteen 87-amino acid repeats, two Arg-Gly-Asp motifs, four cysteine residues, an outer membrane protein domain, a polysaccharide-binding site and several motifs related to cell adhesions. These features are distinct from those of typical repeat-in-toxins and autotransporter adhesins. Real-time quantitative PCR analysis indicates that vva0331 gene expression is activated at 30 degrees C and regulated by iron. In addition, VVA0331 is present primarily in a secreted form as determined by cell fractionation assay and Western blot analysis. No significant difference in Hep2 cell adherence, cytotoxicity, and virulence was observed between the wild type and vva0331 mutant strains. In contrast, these strains exhibited apparently different outer membrane protein profiles, and antiserum raised against C-terminal region of VVA0331 reacted with an 85-kDa outer membrane protein of V. vulnificus YJ016.
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58
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Yang ZN, Xu HJ, Thiem SM, Xu YP, Ge JQ, Tang XD, Tian CH, Zhang CX. Bombyx mori nucleopolyhedrovirus ORF9 is a gene involved in the budded virus production and infectivity. J Gen Virol 2009; 90:162-9. [PMID: 19088285 DOI: 10.1099/vir.0.004903-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The ORF9 of Bombyx mori nucleopolyhedrovirus (BmNPV) (Bm9) is conserved in all completely sequenced lepidopteran nucleopolyhedroviruses. RT-PCR analysis demonstrated that Bm9 is an early and late transcribed gene that is initiated at 3 h post-infection, and immunofluorescence microscopy showed that Bm9 is localized mainly in the cytoplasm of infected cells. To determine the role of Bm9 during virus infection, Bm9 was knocked out by recombination in a BmNPV genome propagated as a bacmid in Escherichia coli. The budded virus (BV) production of Bm9-deleted bacmids was reduced more than 10-fold compared with wild-type (wt) bacmid; however, the kinetics of viral DNA replication were unaffected. The defect in BV production was recovered by the Bm9 rescue bacmid. In addition, electron microscope observations revealed that polyhedra formation was not affected by the deletion of Bm9. Bioassays showed that the Bm9-deleted bacmid took approximately 14-22 h longer to kill fifth instar B. mori larvae than wt bacmid, and the LD(50) was about 15 times higher than that of the wt bacmid. In conclusion, Bm9 is an important but not essential factor in virus production and infectivity in vivo and in vitro.
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Affiliation(s)
- Zhang-Nv Yang
- Institute of Insect Science, Zhejiang University, Kaixuan Road 268, Hangzhou 310029, PR China
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59
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Jia Y, Huan J, Buhr V, Zhang J, Carayannopoulos LN. Towards comprehensive structural motif mining for better fold annotation in the "twilight zone" of sequence dissimilarity. BMC Bioinformatics 2009; 10 Suppl 1:S46. [PMID: 19208148 PMCID: PMC2648771 DOI: 10.1186/1471-2105-10-s1-s46] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Background Automatic identification of structure fingerprints from a group of diverse protein structures is challenging, especially for proteins whose divergent amino acid sequences may fall into the "twilight-" or "midnight-" zones where pair-wise sequence identities to known sequences fall below 25% and sequence-based functional annotations often fail. Results Here we report a novel graph database mining method and demonstrate its application to protein structure pattern identification and structure classification. The biologic motivation of our study is to recognize common structure patterns in "immunoevasins", proteins mediating virus evasion of host immune defense. Our experimental study, using both viral and non-viral proteins, demonstrates the efficiency and efficacy of the proposed method. Conclusion We present a theoretic framework, offer a practical software implementation for incorporating prior domain knowledge, such as substitution matrices as studied here, and devise an efficient algorithm to identify approximate matched frequent subgraphs. By doing so, we significantly expanded the analytical power of sophisticated data mining algorithms in dealing with large volume of complicated and noisy protein structure data. And without loss of generality, choice of appropriate compatibility matrices allows our method to be easily employed in domains where subgraph labels have some uncertainty.
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Affiliation(s)
- Yi Jia
- Department of Electrical Engineering & Computer Science, University of Kansas, Lawrence, KS, 66045, USA.
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60
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Transient shielding of intimin and the type III secretion system of enterohemorrhagic and enteropathogenic Escherichia coli by a group 4 capsule. J Bacteriol 2008; 190:5063-74. [PMID: 18502854 DOI: 10.1128/jb.00440-08] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Enterohemorrhagic and enteropathogenic Escherichia coli (EHEC and EPEC, respectively) strains represent a major global health problem. Their virulence is mediated by the concerted activity of an array of virulence factors including toxins, a type III protein secretion system (TTSS), pili, and others. We previously showed that EPEC O127 forms a group 4 capsule (G4C), and in this report we show that EHEC O157 also produces a G4C, whose assembly is dependent on the etp, etk, and wzy genes. We further show that at early time points postinfection, these G4Cs appear to mask surface structures including intimin and the TTSS. This masking inhibited the attachment of EPEC and EHEC to tissue-cultured epithelial cells, diminished their capacity to induce the formation of actin pedestals, and attenuated TTSS-mediated protein translocation into host cells. Importantly, we found that Ler, a positive regulator of intimin and TTSS genes, represses the expression of the capsule-related genes, including etp and etk. Thus, the expression of TTSS and G4C is conversely regulated and capsule production is diminished upon TTSS expression. Indeed, at later time points postinfection, the diminishing capsule no longer interferes with the activities of intimin and the TTSS. Notably, by using the rabbit infant model, we found that the EHEC G4C is required for efficient colonization of the rabbit large intestine. Taken together, our results suggest that temporal expression of the capsule, which is coordinated with that of the TTSS, is required for optimal EHEC colonization of the host intestine.
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61
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Schlüter A, Krause L, Szczepanowski R, Goesmann A, Pühler A. Genetic diversity and composition of a plasmid metagenome from a wastewater treatment plant. J Biotechnol 2008; 136:65-76. [PMID: 18603322 DOI: 10.1016/j.jbiotec.2008.03.017] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Revised: 03/14/2008] [Accepted: 03/31/2008] [Indexed: 11/24/2022]
Abstract
Plasmid metagenome nucleotide sequence data were recently obtained from wastewater treatment plant (WWTP) bacteria with reduced susceptibility to selected antimicrobial drugs by applying the ultrafast 454-sequencing technology. The sequence dataset comprising 36,071,493 bases (346,427 reads with an average read length of 104 bases) was analysed for genetic diversity and composition by using a newly developed bioinformatic pipeline based on assignment of environmental gene tags (EGTs) to protein families stored in the Pfam database. Short amino acid sequences deduced from the plasmid metagenome sequence reads were compared to profile hidden Markov models underlying Pfam. Obtained matches evidenced that many reads represent genes having predicted functions in plasmid replication, stability and plasmid mobility which indicates that WWTP bacteria harbour genetically stabilised and mobile plasmids. Moreover, the data confirm a high diversity of plasmids residing in WWTP bacteria. The mobile organic peroxide resistance plasmid pMAC from Acinetobacter baumannii was identified as reference plasmid for the most abundant replication module type in the sequenced sample. Accessory plasmid modules encode different transposons, insertion sequences, integrons, resistance and virulence determinants. Most of the matches to Transposase protein families were identified for transposases similar to the one of the chromate resistance transposon Tn5719. Noticeable are hits to beta-lactamase protein families which suggests that plasmids from WWTP bacteria encode different enzymes possessing beta-lactam-hydrolysing activity. Some of the sequence reads correspond to antibiotic resistance genes that were only recently identified in clinical isolates of human pathogens. EGT analysis thus proofed to be a very valuable method to explore genetic diversity and composition of the present plasmid metagenome dataset.
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Affiliation(s)
- Andreas Schlüter
- Department of Genetics, Bielefeld University, Postfach 100131, D-33501 Bielefeld, Germany.
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62
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Isaacson RL, Simpson PJ, Liu M, Cota E, Zhang X, Freemont P, Matthews S. A new labeling method for methyl transverse relaxation-optimized spectroscopy NMR spectra of alanine residues. J Am Chem Soc 2007; 129:15428-9. [PMID: 18041839 DOI: 10.1021/ja0761784] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Rivka L Isaacson
- Division of Molecular Biosciences, Faculty of Natural Sciences, Imperial College London, South Kensington, London, UK
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63
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Vasta GR, Ahmed H, Tasumi S, Odom EW, Saito K. Biological roles of lectins in innate immunity: molecular and structural basis for diversity in self/non-self recognition. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 598:389-406. [PMID: 17892226 DOI: 10.1007/978-0-387-71767-8_27] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Gerardo R Vasta
- University of Maryland Biotechnology Institute, Center of Marine Biotechnology, 701 East Pratt Street, Baltimore, MD 21202, USA.
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64
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Mundy R, Schüller S, Girard F, Fairbrother JM, Phillips AD, Frankel G. Functional studies of intimin in vivo and ex vivo: implications for host specificity and tissue tropism. MICROBIOLOGY (READING, ENGLAND) 2007; 153:959-967. [PMID: 17379706 PMCID: PMC2884948 DOI: 10.1099/mic.0.2006/003467-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2006] [Revised: 11/27/2006] [Accepted: 12/05/2006] [Indexed: 11/18/2022]
Abstract
Intimin is an outer-membrane adhesin that is essential for colonization of the host gastrointestinal tract by attaching and effacing pathogens including enteropathogenic Escherichia coli (EPEC), enterohaemorrhagic E. coli (EHEC) and Citrobacter rodentium (CR). The N-terminus of intimin from the different strains is highly conserved while the C-terminus, which harnesses the active receptor-binding site, shows sequence and antigenic polymorphism. This diversity was used to define a number of distinct intimin types, the most common of which are alpha, beta and gamma. Intimin binds the type III secretion system effector protein Tir. However, a large body of evidence suggests that intimin also binds a host-cell-encoded receptor(s) (Hir), and interaction of different intimin types with Hir contributes to tissue and host specificity. The aims of this study were to compare the activity of the major intimin types (alpha, beta and gamma) in vivo and ex vivo, using the CR mouse model and in vitro organ culture (IVOC), and to determine their exchangeability. The results confirm that intimin gamma is not functional in the CR mouse model. In the pig, intimin beta can substitute for EPEC intimin alpha but when placed in an EHEC O157 : H7 background it does not produce an intimin alpha-like tropism, although some adhesion to the small and large intestine was observed. In contrast, in human IVOC, intimin beta in an EHEC background produces small intestinal colonization in a similar manner to intimin alpha.
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Affiliation(s)
- Rosanna Mundy
- Division of Cell and Molecular Biology, Imperial College London, London, UK
| | - Stephanie Schüller
- Centre for Paediatric Gastroenterology, Royal Free and University College Medical School, London, UK
| | - Francis Girard
- Division of Cell and Molecular Biology, Imperial College London, London, UK
- Groupe de Recherche sur les Maladies Infectieuses du Porc (GREMIP), Faculté de Medicine Vétérinaire, Université de Montréal, St-Hyacinthe, Canada
| | - John M. Fairbrother
- Groupe de Recherche sur les Maladies Infectieuses du Porc (GREMIP), Faculté de Medicine Vétérinaire, Université de Montréal, St-Hyacinthe, Canada
| | - Alan D. Phillips
- Centre for Paediatric Gastroenterology, Royal Free and University College Medical School, London, UK
| | - Gad Frankel
- Division of Cell and Molecular Biology, Imperial College London, London, UK
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Eyer L, Pantůcek R, Zdráhal Z, Konecná H, Kaspárek P, Růzicková V, Hernychová L, Preisler J, Doskar J. Structural protein analysis of the polyvalent staphylococcal bacteriophage 812. Proteomics 2007; 7:64-72. [PMID: 17154272 DOI: 10.1002/pmic.200600280] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Phage 812 is a polyvalent phage with a very broad host range in the genus Staphylococcus, which makes it a suitable candidate for phage therapy of staphylococcal infections. This proteomic study, combining the results of both 1-DE and 2-DE followed by PMF, led to the identification of 24 virion proteins. Twenty new proteins, not yet identified by proteome analysis of closely related staphylococcal phages K and G1 were identified using this approach. Fifteen proteins were assigned unambiguously to the head-tail genome module; the remaining nine proteins are encoded by genes of the left or right arms of the phage genome. As expected, the most abundant proteins in the electrophoretic patterns are the major capsid protein, the major tail sheath protein and proteins identical to ORF 50 and ORF 95 of phage K, although their function is only putative. Identification of these 20 new proteins contributes substantially to a detailed characterization of phage virions, knowledge of which is necessary for rational phage therapy.
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Affiliation(s)
- Ludek Eyer
- Department of Genetics and Molecular Biology, Faculty of Science, Masaryk University, Kotlárská 2, Brno, Czech Republic
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Fraser JS, Yu Z, Maxwell KL, Davidson AR. Ig-like domains on bacteriophages: a tale of promiscuity and deceit. J Mol Biol 2006; 359:496-507. [PMID: 16631788 DOI: 10.1016/j.jmb.2006.03.043] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2005] [Revised: 03/15/2006] [Accepted: 03/17/2006] [Indexed: 11/26/2022]
Abstract
The immunoglobulin (Ig) fold is one of the most important structures in biology, playing essential roles in the vertebrate immune response, cell adhesion, and many other processes. Through bioinformatic analysis, we have discovered that Ig-like domains are often found in the constituent proteins of tailed double-stranded (ds) DNA bacteriophage particles, and are likely displayed on the surface of these viruses. These phage Ig-like domains fall into three distinct sequence families, which are similar to the classic immunoglobulin domain (I-Set), the fibronectin type 3 repeat (FN3), and the bacterial Ig-like domain (Big2). The phage Ig-like domains are very promiscuous. They are attached to more than ten different functional classes of proteins, and found in all three morphogenetic classes of tailed dsDNA phages. In addition, they reside in phages that infect a diverse set of gram negative and gram positive bacteria. These domains are deceptive because many are added to larger proteins through programmed ribosomal frameshifting, so that they are not always detected by standard protein sequence searching procedures. In addition, the presence of unrecognized Ig-like domains in a variety of phage proteins with different functions has led to gene misannotation. Our results demonstrate that horizontal gene transfer involving Ig-like domain encoding DNA has occurred commonly between diverse classes of both lytic and temperate phages, which otherwise display very limited sequence similarities to one another. We suggest that phage may have been an important vector in the spread of Ig-like domains through diverse species of bacteria. While the function of the phage Ig-like domains is unknown, several lines of evidence suggest that they may play an accessory role in phage infection by weakly interacting with carbohydrates on the bacterial cell surface.
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Affiliation(s)
- James S Fraser
- Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ont., Canada M5S 1A8
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Perrier C, Sprenger N, Corthésy B. Glycans on secretory component participate in innate protection against mucosal pathogens. J Biol Chem 2006; 281:14280-7. [PMID: 16543244 DOI: 10.1074/jbc.m512958200] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In mucosal secretions, secretory component (SC) is found either free or bound to polymeric IgA within the secretory IgA complex. SC displays numerous and various glycans, which are potential ligands for bacterial compounds. We first established that human SC (hSC) purified from colostrum (hSCcol) or produced in Chinese hamster ovary cells (hSCrec) exhibits the same lectin reactivity. Both forms bind to Clostridium difficile toxin A and functionally protect polarized Caco-2 cell monolayers from the cytopathic effect of the toxin. The interaction is mediated by glycans present on hSC and involves galactose and sialic acid residues. hSCcol and hSCrec were also shown to bind enteropathogenic Escherichia coli adhesin intimin and to inhibit its infectivity on HEp-2 cells in a glycan-dependent manner as well. SC remained operative in the context of the whole secretory IgA molecule and can therefore enhance its Fab-mediated neutralizing properties. On the contrary, hSC did not interact with three different strains of rotavirus (RF, RRV, and SA11). Accordingly, infection of target MA104 cells with these rotavirus strains was not reduced in the presence of either form of hSC tested. Although not a universal mechanism, these findings identify hSC as a microbial scavenger contributing to the antipathogenic arsenal that protects the body epithelial surfaces.
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Affiliation(s)
- Clémentine Perrier
- R & D Laboratory of the Division of Immunology and Allergy, Centre Hospitalier Universitaire Vaudois, 1011 Lausanne, Switzerland
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68
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Abstract
The superfamily of proteins containing C-type lectin-like domains (CTLDs) is a large group of extracellular Metazoan proteins with diverse functions. The CTLD structure has a characteristic double-loop ('loop-in-a-loop') stabilized by two highly conserved disulfide bridges located at the bases of the loops, as well as a set of conserved hydrophobic and polar interactions. The second loop, called the long loop region, is structurally and evolutionarily flexible, and is involved in Ca2+-dependent carbohydrate binding and interaction with other ligands. This loop is completely absent in a subset of CTLDs, which we refer to as compact CTLDs; these include the Link/PTR domain and bacterial CTLDs. CTLD-containing proteins (CTLDcps) were originally classified into seven groups based on their overall domain structure. Analyses of the superfamily representation in several completely sequenced genomes have added 10 new groups to the classification, and shown that it is applicable only to vertebrate CTLDcps; despite the abundance of CTLDcps in the invertebrate genomes studied, the domain architectures of these proteins do not match those of the vertebrate groups. Ca2+-dependent carbohydrate binding is the most common CTLD function in vertebrates, and apparently the ancestral one, as suggested by the many humoral defense CTLDcps characterized in insects and other invertebrates. However, many CTLDs have evolved to specifically recognize protein, lipid and inorganic ligands, including the vertebrate clade-specific snake venoms, and fish antifreeze and bird egg-shell proteins. Recent studies highlight the functional versatility of this protein superfamily and the CTLD scaffold, and suggest further interesting discoveries have yet to be made.
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Affiliation(s)
- Alex N Zelensky
- Computational Proteomics and Therapy Design Group, John Curtin School of Medical Research, Australian National University, Canberra, Australia
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69
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Abstract
Enterohemorrhagic Escherichia coli (EHEC) was first recognized as a cause of human disease in 1983 and is associated with diarrhea and hemorrhagic colitis, which may be complicated by life-threatening renal and neurological sequelae. EHEC are defined by their ability to produce one or more Shiga-like toxins (Stx), which mediate the systemic complications of EHEC infections, and to induce characteristic attaching and effacing lesions on intestinal epithelia, a phenotype that depends on the locus of enterocyte effacement. Acquisition of Stx-encoding bacteriophages by enteropathogenic E. coli is believed to have contributed to the evolution of EHEC, and consequently some virulence factors are conserved in both pathotypes. A key requirement for E. coli to colonize the intestines and produce disease is the ability to adhere to epithelial cells lining the gastrointestinal tract. Here, we review knowledge of the adhesins produced by EHEC and other Stx-producing E. coli, with emphasis on genetic, structural, and mechanistic aspects and their contribution to pathogenesis.
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Affiliation(s)
- Mark P Stevens
- Division of Microbiology, Institute for Animal Health, Compton Laboratory, Berkshire RG20 7NN, United Kingdom
| | - Timothy S Wallis
- Division of Microbiology, Institute for Animal Health, Compton Laboratory, Berkshire RG20 7NN, United Kingdom
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70
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Girard F, Batisson I, Frankel GM, Harel J, Fairbrother JM. Interaction of enteropathogenic and Shiga toxin-producing Escherichia coli and porcine intestinal mucosa: role of intimin and Tir in adherence. Infect Immun 2005; 73:6005-16. [PMID: 16113321 PMCID: PMC1231093 DOI: 10.1128/iai.73.9.6005-6016.2005] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The ileal in vitro organ culture (IVOC) model using tissues originating from colostrum-deprived newborn piglets has proven to be an effective way to study the attaching and effacing (A/E) phenotype of porcine enteropathogenic Escherichia coli (EPEC) ex vivo. The aim of this study was to investigate the role of intimin subtype and Tir in the adherence of EPEC and Shiga-toxin-producing E. coli (STEC), isolated from different animal species, to porcine intestinal IVOC. Moreover, the role of intimin in Tir-independent adherence of the human EPEC strain E2348/69 was investigated using intimin and Tir-deficient derivatives. Our results demonstrated that A/E E. coli strains (AEEC) from various animal species and humans induce the A/E phenotype in porcine ileal IVOC and that intimin subtype influences intestinal adherence and tropism of AEEC strains. We also showed that a tir mutant of EPEC strain E2348/69 demonstrates close adherence to the epithelial cells of porcine ileal IVOC segments, with microvillous effacement but with no evidence of actin polymerization or pedestal formation, and that intimin seems to be involved in this phenotype. Overall, this study provides further evidence for the existence of one or more host-cell-encoded intimin receptor(s) in the pig gut.
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Affiliation(s)
- Francis Girard
- Groupe de Recherche sur les Maladies Infectieuses du Porc, Département de Pathologie et Microbiologie, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe, Canada
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71
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Niemann HH, Schubert WD, Heinz DW. Adhesins and invasins of pathogenic bacteria: a structural view. Microbes Infect 2005; 6:101-12. [PMID: 14738899 DOI: 10.1016/j.micinf.2003.11.001] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Adhesion and invasion of pathogenic bacteria represent the important initial step of infection. Pathogens utilize surface-located adhesins/invasins for specific interaction with host cell receptors. The three-dimensional structures of a number of adhesins/invasins show that many are elongated molecules containing domains commonly found in eukaryotic proteins. Similar folds are employed repeatedly to target different receptors.
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Affiliation(s)
- Hartmut H Niemann
- Department of Structural Biology, German Research Center for Biotechnology (GBF), Mascheroder Weg 1, 38124, Braunschweig, Germany
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72
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Morais MC, Choi KH, Koti JS, Chipman PR, Anderson DL, Rossmann MG. Conservation of the Capsid Structure in Tailed dsDNA Bacteriophages: the Pseudoatomic Structure of ϕ29. Mol Cell 2005; 18:149-59. [PMID: 15837419 DOI: 10.1016/j.molcel.2005.03.013] [Citation(s) in RCA: 150] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2004] [Revised: 02/22/2005] [Accepted: 03/16/2005] [Indexed: 11/26/2022]
Abstract
Bacteriophage phi29 is one of the smallest and simplest known dsDNA phages, making it amenable to structural investigations. The three-dimensional structure of a fiberless, isometric variant has been determined to 7.9 A resolution by cryo-electron microscopy (cryo-EM), allowing the identification of alpha helices and beta sheets. Their arrangement indicates that the folds of the phi29 and bacteriophage HK97 capsid proteins are similar except for an additional immunoglobulin-like domain of the phi29 protein. An atomic model that incorporates these two domains fits well into the cryo-EM density of the T = 3, fiberless isometric phi29 particle, and cryo-EM structures of fibered isometric and fiberless prolate prohead phi29 particles at resolutions of 8.7 A and 12.7 A, respectively. Thus, phi29 joins the growing number of phages that utilize the HK97 capsid structure, suggesting that this protein fold may be as prevalent in capsids of dsDNA phages as the jelly roll fold is in eukaryotic viruses.
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Affiliation(s)
- Marc C Morais
- Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, Indiana 47907, USA
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73
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Torres AG, Zhou X, Kaper JB. Adherence of diarrheagenic Escherichia coli strains to epithelial cells. Infect Immun 2005; 73:18-29. [PMID: 15618137 PMCID: PMC538947 DOI: 10.1128/iai.73.1.18-29.2005] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Alfredo G Torres
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-1070, USA.
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74
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Chen HD, Frankel G. EnteropathogenicEscherichia coli: unravelling pathogenesis. FEMS Microbiol Rev 2005; 29:83-98. [PMID: 15652977 DOI: 10.1016/j.femsre.2004.07.002] [Citation(s) in RCA: 234] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2004] [Revised: 07/27/2004] [Accepted: 07/27/2004] [Indexed: 01/05/2023] Open
Abstract
Enteropathogenic Escherichia coli (EPEC) is a gram-negative bacterial pathogen that adheres to intestinal epithelial cells, causing diarrhoea. It constitutes a significant risk to human health and remains an important cause of infant mortality in developing countries. Although EPEC was the first E. coli strain to be implicated in human disease in the 1940s and 1950s, the mechanisms by which this pathogen induced diarrhoea remained a complete mystery throughout most of the 40 years since its description. It was only during the late 1980s that major advances were made in unravelling the mechanisms behind EPEC pathogenesis. Ever since, progress has been made at a stunning pace and there have been major breakthroughs in identifying the bacterial factors involved in attaching and effacing (A/E) lesion formation, host signal transduction pathways in response to EPEC infection and the genetic basis of EPEC pathogenesis. The rapid pace of discovery is a result of intensive research by investigators in this field and portends that EPEC will soon be among one of the most understood diarrhoea-causing infectious agents. This review aims to trace the progress of EPEC research since its existence was first reported by John Bray in 1945, highlighting the major findings that have revolutionised our understanding of EPEC pathogenesis.
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Affiliation(s)
- Huiwen Deborah Chen
- Department of Biological Sciences, Centre for Molecular Microbiology and Infection, Imperial College London, Flowers Building, London SW7 2AZ, UK
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75
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Koizumi N, Watanabe H. Leptospiral immunoglobulin-like proteins elicit protective immunity. Vaccine 2004; 22:1545-52. [PMID: 15063580 DOI: 10.1016/j.vaccine.2003.10.007] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2003] [Revised: 09/16/2003] [Accepted: 10/06/2003] [Indexed: 11/21/2022]
Abstract
The identification of new vaccine candidates for leptospirosis is of great interest. This paper describes the identification of two homologous immunogenic proteins, LigA-m and LigB-m, of Leptospira interrogans serovar manilae strain UP-MMC-NIID, which show strong similarity with LigA found recently in L. interrogans serovar pomona. Southern blot analysis indicated the conservation of the lig genes among pathogenic leptospires. LigA-m protein was shown to be a surface-exposed lipoprotein expressed during in vitro culture. Both LigA-m and LigB-m induced protective immunity against a challenge with a homologous serovar of L. interrogans in mice. Furthermore, patients' sera infected with heterologous serovars' strains contained antibodies against LigA-m and LigB-m. Our results suggest that LigA-m and LigB-m proteins are new vaccine candidates for the prevention of leptospirosis.
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Affiliation(s)
- Nobuo Koizumi
- Department of Bacteriology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan.
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76
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Labrou NE, Rigden DJ. The structure-function relationship in the clostripain family of peptidases. ACTA ACUST UNITED AC 2004; 271:983-92. [PMID: 15009210 DOI: 10.1111/j.1432-1033.2004.04000.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this study we investigate the active-site structure and the catalytic mechanism of clostripain by using a combination of three separate techniques: affinity labelling, site-directed mutagenesis and molecular modelling. A benzamidinyl-diazo dichlorotriazine dye (BDD) was shown to act as an efficient active site-directed affinity label for Clostridium histolyticum clostripain. The enzyme, upon incubation with BDD in 0.1 m Hepes/NaOH buffer pH 7.6, exhibits a time-dependent loss of activity. The rate of inactivation exhibits a nonlinear dependence on the BDD concentration, which can be described by reversible binding of dye to the enzyme prior to the irreversible reaction. The dissociation constant of the reversible formation of an enzyme-BDD complex is KD = 74.6 +/- 2.1 micro m and the maximal rate constant of inactivation is k3 = 0.21 x min(-1). Effective protection against inactivation by BDD is provided by the substrate N-benzoyl-L-arginine ethyl ester (BAEE). Cleavage of BDD-modified enzyme with trypsin and subsequent separation of peptides by reverse-phase HPLC gave only one modified peptide. Amino acid sequencing of the modified tryptic peptide revealed the target site of BDD reaction to be His176. Site-directed mutagenesis was used to study further the functional role of His176. The mutant His176Ala enzyme exhibited zero activity against BAEE. Together with previous data, these results confirm that a catalytic dyad of His176 and Cys231 is responsible for cysteine peptidase activity in the C11 peptidase family. A molecular model of the catalytic domain of clostripain was constructed using a manually extended fold recognition-derived alignment with caspases. A rigorous iterative modelling scheme resulted in an objectively sound model which points to Asp229 as responsible for defining the strong substrate specificity for Arg at the P1 position. Two possible binding sites for the calcium required for auto-activation could be located. Database searches show that clostripain homologues are not confined to bacterial lineages and reveal an intriguing variety of domain architectures.
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Affiliation(s)
- Nikolaos E Labrou
- Laboratory of Enzyme Technology, Department of Agricultural Biotechnology, Agricultural University of Athens, Greece.
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77
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Zelensky AN, Gready JE. Comparative analysis of structural properties of the C-type-lectin-like domain (CTLD). Proteins 2003; 52:466-77. [PMID: 12866057 DOI: 10.1002/prot.10626] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The superfamily of proteins containing the C-type-lectin-like domain (CTLD) is a group of abundant extracellular metazoan proteins characterized by evolutionary flexibility and functional versatility. Several CTLDs are also found in parasitic prokaryotes and viruses. The 37 distinct currently available CTLD structures demonstrate significant structural conservation despite low or undetectable sequence similarity. Our aim in this study was to perform an extensive comparative analysis of all available CTLD structures to establish the most conserved structural features of the fold, and to test and extend the early analysis of Drickamer. By implication, these features should be those critical for maintenance of integrity of the fold. By analyzing CTLD structures superimposed by several methods, we have established groups of conserved structural positions involved in fold maintenance but not in ligand binding; these are consistent with the fold's known functional flexibility. In addition to the well-recognized disulfide bridges, groups of conserved residues are involved in hydrophobic interactions stabilizing the core of the fold and the long loop region, and in an alpha2-beta1-beta5 polar interaction. Evaluation of the conclusions of the structure comparison study compared with alignments of all available human, mouse and Caenorhabditis elegans CTLD sequences showed that conservation patterns are preserved throughout the whole CTLD sequence space. Our observations provide an improved understanding of CTLD structure, and will help in identification of new CTLDs and the mechanisms that drive and constrain the coevolution of the structure and function of the fold.
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Affiliation(s)
- Alex N Zelensky
- Computational Proteomics and Therapy Design Group, John Curtin School of Medical Research, Australian National University, Canberra ACT, Australia
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78
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Cohen M, Feinstein N, Wilson KL, Gruenbaum Y. Nuclear pore protein gp210 is essential for viability in HeLa cells and Caenorhabditis elegans. Mol Biol Cell 2003; 14:4230-7. [PMID: 14517331 PMCID: PMC207014 DOI: 10.1091/mbc.e03-04-0260] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Gp210 is an evolutionarily conserved membrane protein of the nuclear pore complex (NPC). We studied the phenotypes produced by RNAi-induced downregulation of gp210 in both human (HeLa) cells and Caenorhabditis elegans embryos. HeLa cell viability requires Gp210 activity. The dying cells accumulated clustered NPCs and aberrant membrane structures at the nuclear envelope, suggesting that gp210 is required directly or indirectly for nuclear pore formation and dilation as well as the anchoring or structural integrity of mature NPCs. Essential roles for gp210 were confirmed in C. elegans, where RNAi-induced reduction of gp210 caused embryonic lethality. The nuclear envelopes of embryos with reduced gp210 also had aberrant nuclear membrane structures and clustered NPCs, confirming that gp210 plays critical roles at the nuclear membrane through mechanisms that are conserved from nematodes to humans.
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Affiliation(s)
- Merav Cohen
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, 91904 Israel
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79
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Daniell SJ, Kocsis E, Morris E, Knutton S, Booy FP, Frankel G. 3D structure of EspA filaments from enteropathogenic Escherichia coli. Mol Microbiol 2003; 49:301-8. [PMID: 12828630 DOI: 10.1046/j.1365-2958.2003.03555.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The type III secretion system (TTSS) is a modular apparatus assembled by many pathogenic Gram-negative bacteria and is designed to translocate proteins through the bacterial cell wall into the eukaryotic host cell. The conserved components of the TTSS comprise stacks of rings spanning the inner and outer bacterial membrane and a narrow, needle-like structure projecting outwards. The TTSS of enteropathogenic E. coli is unique in that one of the translocator proteins, EspA, polymerizes to form an extension to the needle complex which interacts with the host cell. In this study we present the 3D structure of EspA filaments to c. 26 A resolution determined from electron micrographs of negatively stained preparations by image processing. The structure comprises a helical tube with a diameter of 120 A enclosing a central channel of 25 A diameter through which effector proteins may be transported. The subunit arrangement corresponds to a one-start helix with 28 subunits present in five turns of the helix and an axial rise of 4.6 A per subunit. This is the first report of a 3D structure of a filamentous extension to the TTSS.
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Affiliation(s)
- Sarah J Daniell
- Centre for Molecular Microbiology and Infection, Department of Biological Sciences, Imperial College, London, SW7 2AZ, UK
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80
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Clarke SC, Haigh RD, Freestone PPE, Williams PH. Virulence of enteropathogenic Escherichia coli, a global pathogen. Clin Microbiol Rev 2003; 16:365-78. [PMID: 12857773 PMCID: PMC164217 DOI: 10.1128/cmr.16.3.365-378.2003] [Citation(s) in RCA: 152] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Enteropathogenic Escherichia coli (EPEC) remains an important cause of diarrheal disease worldwide. Research into EPEC is intense and provides a good virulence model of other E. coli infections as well as other pathogenic bacteria. Although the virulence mechanisms are now better understood, they are extremely complex and much remains to be learnt. The pathogenesis of EPEC depends on the formation of an ultrastructural lesion in which the bacteria make intimate contact with the host apical enterocyte membrane. The formation of this lesion is a consequence of the ability of EPEC to adhere in a localized manner to the host cell, aided by bundle-forming pili. Tyrosine phosphorylation and signal transduction events occur within the host cell at the lesion site, leading to a disruption of the host cell mechanisms and, consequently, to diarrhea. These result from the action of highly regulated EPEC secreted proteins which are released via a type III secretion system, many genes of which are located within a pathogenicity island known as the locus of enterocyte effacement. Over the last few years, dramatic increases in our knowledge of EPEC virulence have taken place. This review therefore aims to provide a broad overview of and update to the virulence aspects of EPEC.
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Affiliation(s)
- S C Clarke
- Scottish Meningococcus and Pneumococcus Reference Laboratory, Glasgow University, Glasgow, United Kingdom.
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81
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Abstract
Enteropathogenic Escherichia coli (EPEC) adhere to the intestinal mucosa and to tissue culture cells in a distinctive fashion, destroying microvilli, altering the cytoskeleton and attaching intimately to the host cell membrane in a manner termed the attaching and effacing effect. Typical EPEC strains also form three-dimensional microcolonies in a pattern termed localized adherence. Attaching and effacing, and in particular intimate attachment requires an outer membrane adhesin called intimin, which binds to the translocated intimin receptor, Tir. Tir is produced by the bacteria and delivered to the host cell via a type III secretion system. In addition to this well-established adhesin-receptor pair, numerous other adhesin interactions between EPEC and host cells have been described including those between intimin and cellular receptors and those involving a bundle-forming pilus and flagella and unknown receptors. Much additional work is needed before a full understanding of EPEC adhesion to host cells comes to light.
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Affiliation(s)
- Jean-Philippe Nougayrède
- Division of Infectious Diseases, University of Maryland, Baltimore, 10 S Pine Street, Baltimore, MD 21201, USA
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82
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Barnhart MM, Sauer FG, Pinkner JS, Hultgren SJ. Chaperone-subunit-usher interactions required for donor strand exchange during bacterial pilus assembly. J Bacteriol 2003; 185:2723-30. [PMID: 12700251 PMCID: PMC154394 DOI: 10.1128/jb.185.9.2723-2730.2003] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The assembly of type 1 pili on the surface of uropathogenic Escherichia coli proceeds via the chaperone-usher pathway. Chaperone-subunit complexes interact with one another via a process termed donor strand complementation whereby the G1beta strand of the chaperone completes the immunoglobulin (Ig) fold of the pilus subunit. Chaperone-subunit complexes are targeted to the usher, which forms a channel across the outer membrane through which pilus subunits are translocated and assembled into pili via a mechanism known as donor strand exchange. This is a mechanism whereby chaperone uncapping from a subunit is coupled with the simultaneous assembly of the subunit into the pilus fiber. Thus, in the pilus fiber, the N-terminal extension of every subunit completes the Ig fold of its neighboring subunit by occupying the same site previously occupied by the chaperone. Here, we investigated details of the donor strand exchange assembly mechanism. We discovered that the information necessary for targeting the FimC-FimH complex to the usher resides mainly in the FimH protein. This interaction is an initiating event in pilus biogenesis. We discovered that the ability of an incoming subunit (in a chaperone-subunit complex) to participate in donor strand exchange with the growing pilus depended on a previously unrecognized function of the chaperone. Furthermore, the donor strand exchange assembly mechanism between subunits was found to be necessary for subunit translocation across the outer membrane usher.
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Affiliation(s)
- Michelle M Barnhart
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110-1093, USA
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83
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MacDonald TT, Frankel G, Dougan G, Goncalves NS, Simmons C. Host defences to Citrobacter rodentium. Int J Med Microbiol 2003; 293:87-93. [PMID: 12755369 DOI: 10.1078/1438-4221-00247] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Citrobacter rodentium is a natural non-invasive bacterial pathogen which infects the distal colon of mice. It uses the same molecular mechanisms of type III secretion as human enteropathogenic and enterohemorrhagic Escherichia coli to colonise the epithelial cells of the gut and is therefore an ideal model to study host-bacterial pathogen interactions in vivo. Infection elicits mucosal inflammation with similarities to inflammatory bowel disease, and so it is a readily accessible model to investigate the relationship between inflammation and anti-bacterial immunity in the gut.
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Affiliation(s)
- Thomas T MacDonald
- Division of Infection, Inflammation and Repair, University of Southampton School of Medicine, Southampton General Hospital, Southampton, UK.
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84
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Hickey RM, Twomey DP, Ross RP, Hill C. Production of enterolysin A by a raw milk enterococcal isolate exhibiting multiple virulence factors. MICROBIOLOGY (READING, ENGLAND) 2003; 149:655-664. [PMID: 12634334 DOI: 10.1099/mic.0.25949-0] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Even though enterococci are a common cause of human infection they can readily be isolated from a range of food sources, including various meat and dairy products. An enterococcal strain, DPC5280, which exhibits a broad spectrum of inhibition against many Gram-positive bacteria was recently isolated from an Irish raw milk sample. Characterization of the inhibition revealed that the strain exhibits haemolytic activity characteristic of the two-component lantibiotic cytolysin and also produces a heat-labile antimicrobial protein of 34 kDa. The latter protein displayed cell wall hydrolytic activity, as evidenced by zymogram gels containing autoclaved lactococcal cells. N-terminal sequencing of the purified protein yielded the sequence ASNEWS which is 100 % identical to enterolysin A (accession no. AF249740), a protein which shares 28 and 29 % identity to the Gly-Gly endopeptidases, lysostaphin and zoocin A, respectively. Indeed, amplification of entL from DPC5280 and sequencing revealed that the protein is 100 % identical to enterolysin A. The DPC5280 strain also contained the determinants associated with multiple virulence factors, including gelatinase, aggregation substance and multiple antibiotic resistance. The linkage of this cell-wall-degrading enzyme to other virulence factors in enterococci may contribute to the competitiveness of pathogenic enterococci when found in complex microbial environments such as food and the gastrointestinal tract.
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Affiliation(s)
- Rita M Hickey
- Microbiology Department, University College Cork, Ireland
- Teagasc, Dairy Products Research Centre, Moorepark, Fermoy, Co. Cork, Ireland
| | - Denis P Twomey
- National Food Biotechnology Centre, University College Cork, Ireland
- Teagasc, Dairy Products Research Centre, Moorepark, Fermoy, Co. Cork, Ireland
| | - R Paul Ross
- Teagasc, Dairy Products Research Centre, Moorepark, Fermoy, Co. Cork, Ireland
| | - Colin Hill
- Microbiology Department, University College Cork, Ireland
- National Food Biotechnology Centre, University College Cork, Ireland
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85
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Reece S, Simmons CP, Fitzhenry RJ, Ghaem-Maghami M, Mundy R, Hale C, Matthews S, Dougan G, Phillips AD, Frankel G. Tyrosine residues at the immunoglobulin-C-type lectin inter-domain boundary of intimin are not involved in Tir-binding but implicated in colonisation of the host. Microbes Infect 2002; 4:1389-99. [PMID: 12475629 DOI: 10.1016/s1286-4579(02)00021-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Intimin is an outer membrane adhesion molecule involved in bacterial adhesion to intestinal epithelium by several human and animal enteric pathogens, including enteropathogenic and enterohaemorrhagic Escherichia coli and Citrobacter rodentium. Intimin binds to the translocated intimin receptor, Tir, which is delivered to the plasma membrane of the host cell by a type III protein translocation system. Intimin is also implicated in binding to a host cell-encoded intimin receptor (Hir). The receptor-binding activity of intimin resides within the carboxy terminus 280 amino acids (Int280) of the polypeptide. Structural analysis of this region revealed two immunoglobulin-like domains, the second of which forms a number of contacts with the distal C-type lectin-like module. Specific orientation differences at this inter-domain boundary, which consists of several tyrosine residues, were detected between the crystal and solution structures. In this study, we determined the influence of site-directed mutagenesis of each of four tyrosine residues on intimin-Tir interactions and on intimin-mediated intimate attachment. The mutant intimins were also studied using a variety of in vitro and in vivo infection models. The results show that three of the four Tyr, although not essential for A/E lesion formation in vitro, are required for efficient colonisation of the mouse host following oral challenge.
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MESH Headings
- Adhesins, Bacterial/chemistry
- Adhesins, Bacterial/isolation & purification
- Adhesins, Bacterial/physiology
- Animals
- Binding Sites
- Carrier Proteins/chemistry
- Carrier Proteins/isolation & purification
- Carrier Proteins/physiology
- Cells, Cultured
- Citrobacter freundii/genetics
- Citrobacter freundii/metabolism
- Escherichia coli/growth & development
- Escherichia coli/metabolism
- Escherichia coli/pathogenicity
- Escherichia coli Proteins/metabolism
- Female
- Gene Deletion
- Humans
- Immunoglobulins/chemistry
- Intestines/immunology
- Intestines/ultrastructure
- Lectins, C-Type/chemistry
- Mice
- Mice, Inbred C3H
- Microscopy, Electron, Scanning
- Models, Biological
- Mutagenesis, Site-Directed/genetics
- Plant Lectins/immunology
- Protein Binding
- Protein Conformation
- Protein Structure, Tertiary
- Receptors, Cell Surface/metabolism
- Tyrosine/chemistry
- Tyrosine/physiology
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Affiliation(s)
- Stephen Reece
- Centre for Molecular Microbiology and Infection, Department of Biological Sciences, Flowers Building, Imperial College of Science, Technology and Medicine, London SW7 2AZ, UK
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86
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Palaniappan RUM, Chang YF, Jusuf SSD, Artiushin S, Timoney JF, McDonough SP, Barr SC, Divers TJ, Simpson KW, McDonough PL, Mohammed HO. Cloning and molecular characterization of an immunogenic LigA protein of Leptospira interrogans. Infect Immun 2002; 70:5924-30. [PMID: 12379666 PMCID: PMC130282 DOI: 10.1128/iai.70.11.5924-5930.2002] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A clone expressing a novel immunoreactive leptospiral immunoglobulin-like protein A of 130 kDa (LigA) from Leptospira interrogans serovar pomona type kennewicki was isolated by screening a genomic DNA library with serum from a mare that had recently aborted due to leptospiral infection. LigA is encoded by an open reading frame of 3,675 bp, and the deduced amino acid sequence consists of a series of 90-amino-acid tandem repeats. A search of the NCBI database found that homology of the LigA repeat region was limited to an immunoglobulin-like domain of the bacterial intimin binding protein of Escherichia coli, the cell adhesion domain of Clostridium acetobutylicum, and the invasin of Yersinia pestis. Secondary structure prediction analysis indicates that LigA consists mostly of beta sheets with a few alpha-helical regions. No LigA was detectable by immunoblot analysis of lysates of the leptospires grown in vitro at 30 degrees C or when cultures were shifted to 37 degrees C. Strikingly, immunohistochemistry on kidney from leptospira-infected hamsters demonstrated LigA expression. These findings suggest that LigA is specifically induced only in vivo. Sera from horses, which aborted as a result of natural Leptospira infection, strongly recognize LigA. LigA is the first leptospiral protein described to have 12 tandem repeats and is also the first to be expressed only during infection. Thus, LigA may have value in serodiagnosis or as a protective immunogen in novel vaccines.
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87
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Smith DGE, Naylor SW, Gally DL. Consequences of EHEC colonisation in humans and cattle. Int J Med Microbiol 2002; 292:169-83. [PMID: 12398208 DOI: 10.1078/1438-4221-00202] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
While many factors have been associated with human EHEC infection, the full role these play in both human and ruminant hosts are not yet clear despite much investigation. It is hoped that the continued intense international research effort into EHEC will provide further insights into the commensal versus pathogenic lifestyles of E. coli and lead to approaches to reduce EHEC carriage in ruminants as well as prevent or treat human disease.
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Affiliation(s)
- David G E Smith
- Medical Microbiology, Royal (Dick) School of Veterinary Studies, University of Edinburgh, United Kingdom
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88
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Liu H, Radhakrishnan P, Magoun L, Prabu M, Campellone KG, Savage P, He F, Schiffer CA, Leong JM. Point mutants of EHEC intimin that diminish Tir recognition and actin pedestal formation highlight a putative Tir binding pocket. Mol Microbiol 2002; 45:1557-73. [PMID: 12354225 DOI: 10.1046/j.1365-2958.2002.03137.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Attachment to host cells by enterohaemorrhagic Escherichia coli (EHEC) is associated with the formation of a highly organized cytoskeletal structure containing filamentous actin, termed an attaching and effacing (AE) lesion. Intimin, an outer membrane protein of EHEC, is required for the formation of AE lesions, as is Tir, a bacterial protein that is translocated into the host cell to function as a receptor for intimin. We established a yeast two-hybrid assay for intimin-Tir interaction and, after random mutagenesis, isolated 24 point mutants in intimin, which disrupted Tir recognition in this system. Analysis of 11 point mutants revealed a correlation between recognition of recombinant Tir and the ability to trigger AE lesions. Many of the mutations fell within a 50-residue region near the C-terminus of intimin. Alanine-scanning mutagenesis of this region revealed four residues (Ser890, Thr909, Asn916 and Asn927) that are critical for Tir recognition. Mapping the sequences of EHEC intimin and Tir onto the crystal structure of the intimin-Tir complex of enteropathogenic E. coli predicts that each of these four intimin residues lies at the intimin-Tir interface and contributes to a pocket that interacts with Ile298 of EHEC Tir. Thus, this genetic approach to intimin function both identified residues critical for Tir binding and demonstrated a correlation between the ability to bind Tir and the ability to trigger actin focusing.
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Affiliation(s)
- Hui Liu
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worchester, MA, USA
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89
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Fitzhenry RJ, Reece S, Trabulsi LR, Heuschkel R, Murch S, Thomson M, Frankel G, Phillips AD. Tissue tropism of enteropathogenic Escherichia coli strains belonging to the O55 serogroup. Infect Immun 2002; 70:4362-8. [PMID: 12117946 PMCID: PMC128144 DOI: 10.1128/iai.70.8.4362-4368.2002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Four enteropathogenic Escherichia coli (EPEC) strains belonging to the O55 serogroup (G21 and G30 [both O55:H6], G35 [O55:H-], and G58 [O55:H7]) were tested for their tissue tropism by using human intestinal in vitro organ culture. Strains showed restricted adhesion with attaching-and-effacing activity to follicle-associated epithelium of Peyer's patches, with no apparent adhesion to duodenum or colon. G35 and G58 express intimin gamma and show a similar tropism to intimin gamma-expressing enterohemorrhagic E. coli (EHEC) O157:H7. However, strains G21 and G30 were unusual because they expressed intimin alpha and had a restricted tissue tropism of intimin gamma phenotype. The amino acid sequence of the carboxy-terminal 280 amino acids of intimin from G21 was determined. Comparison with the prototype intimin alpha from strain E2348/69 (O127:H6) showed a single amino acid difference (corresponding to Val907 and Ala907 in the whole intimins). This mutation was reproduced by site-directed mutagenesis in an intimin alpha plasmid template, pCVD438, with the hypothesis that it may induce a change in tropism. However, when the mutated plasmid was placed in both EPEC and EHEC backgrounds, duodenal adhesion in a manner similar to strain E2348/69 was evident upon in vitro organ culture. Thus, additional factor(s) unrelated to intimin exist in the O55:H6 genome that influence human intestinal tissue tropism.
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Affiliation(s)
- R J Fitzhenry
- Centre for Paediatric Gastroenterology, Royal Free Hospital and University College Medical School, London, United Kingdom
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90
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Yuan X, Werner JM, Lack J, Knott V, Handford PA, Campbell ID, Downing AK. Effects of the N2144S mutation on backbone dynamics of a TB-cbEGF domain pair from human fibrillin-1. J Mol Biol 2002; 316:113-25. [PMID: 11829507 DOI: 10.1006/jmbi.2001.5329] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The calcium-binding epidermal growth factor-like (cbEGF) module and the transforming growth factor beta-binding protein-like (TB) module are the two major structural motifs found in fibrillin-1, the extracellular matrix (ECM) protein defective in the Marfan syndrome (MFS). An MFS-causing mutation, N2144S, which removes a calcium ligand in cbEGF32, does not detectably affect fibrillin-1 biosynthesis, rate of secretion, processing, or deposition of reducible fibrillin-1 into the ECM. Since the residue at position 2144 is normally engaged in calcium ligation, it is unable to mediate intermolecular interactions. We have shown previously that this mutation does not affect the folding properties of the TB or cbEGF domains in vitro, but does decrease calcium-binding in cbEGF and TB-cbEGF domain constructs. Here, we use NMR spectroscopy to probe the effects of the N2144S mutation on backbone dynamic properties of TB6-cbEGF32. Analysis of the backbone (15)N relaxation data of wild-type TB6-cbEGF32 has revealed a flexible inter-domain linkage. Parallel dynamics analysis of the N2144S mutant has shown increased flexibility in the region joining the two domains as well as in the calcium-binding site at the N terminus of cbEGF32. This research demonstrates that a small change in peptide backbone flexibility, which does not enhance proteolytic susceptibility of the domain pair, is associated with an MFS phenotype. Flexibility of the TB-cbEGF linkage is likely to contribute to the biomechanical properties of fibrillin-rich connective tissue microfibrils, and may play a role in the microfibril assembly process.
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Affiliation(s)
- Xuemei Yuan
- Department of Biochemistry, University of Oxford, UK
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91
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Sinclair JF, O'Brien AD. Cell surface-localized nucleolin is a eukaryotic receptor for the adhesin intimin-gamma of enterohemorrhagic Escherichia coli O157:H7. J Biol Chem 2002; 277:2876-85. [PMID: 11704679 DOI: 10.1074/jbc.m110230200] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Intimin-gamma is an outer membrane protein of enterohemorrhagic Escherichia coli (EHEC) O157:H7 that is required for the organism to adhere tightly to HEp-2 cells and to colonize experimental animals. Another EHEC O157:H7 protein, the Transferred intimin receptor (Tir), is considered the primary receptor for intimin-gamma. Nevertheless, Tir-independent binding of intimin-gamma to HEp-2 cells has been reported. This observation suggests the existence of a eukaryotic receptor(s) for intimin-gamma. In this study, we sought to identify that receptor(s). First, we determined by equilibrium binding titration that the association of purified intimin-gamma with HEp-2 cells was specific and consistent with a single host cell receptor. Second, we isolated a protein from lysates of HEp-2 cells that bound intimin-gamma and subsequently identified this molecule as nucleolin, a protein involved in cell growth regulation that can be cell surface-expressed. Third, we established that purified intimin-gamma and nucleolin were co-localized on the surface of HEp-2 cells and that the site of EHEC O157:H7 attachment was associated with regions of nucleolin expression. Finally, we demonstrated that mouse anti-nucleolin sera significantly decreased the adherence of EHEC O157:H7 to HEp-2 cells. From this, we conclude that nucleolin is the HEp-2 cell receptor for intimin-gamma expressed by EHEC O157:H7.
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Affiliation(s)
- James F Sinclair
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814-4799, USA
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92
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Wentzel A, Christmann A, Adams T, Kolmar H. Display of passenger proteins on the surface of Escherichia coli K-12 by the enterohemorrhagic E. coli intimin EaeA. J Bacteriol 2001; 183:7273-84. [PMID: 11717287 PMCID: PMC95577 DOI: 10.1128/jb.183.24.7273-7284.2001] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Intimins are members of a family of bacterial adhesins from pathogenic Escherichia coli which specifically interact with diverse eukaryotic cell surface receptors. The EaeA intimin from enterohemorrhagic E. coli O157:H7 contains an N-terminal transporter domain, which resides in the bacterial outer membrane and promotes the translocation of four C-terminally attached passenger domains across the bacterial cell envelope. We investigated whether truncated EaeA intimin lacking two carboxy-terminal domains could be used as a translocator for heterologous passenger proteins. We found that a variant of the trypsin inhibitor Ecballium elaterium trypsin inhibitor II (EETI-II), interleukin 4, and the Bence-Jones protein REI(v) were displayed on the surface of E. coli K-12 via fusion to truncated intimin. Fusion protein net accumulation in the outer membrane could be regulated over a broad range by varying the cellular amount of suppressor tRNA that is necessary for translational readthrough at an amber codon residing within the truncated eaeA gene. Intimin-mediated adhesion of the bacterial cells to eukaryotic target cells could be mimicked by surface display of a short fibrinogen receptor binding peptide containing an arginine-glycine-aspartic acid sequence motif, which promoted binding of E. coli K-12 to human platelets. Cells displaying a particular epitope sequence fused to truncated intimin could be enriched 200,000-fold by immunofluorescence staining and fluorescence-activated cell sorting in three sorting rounds. These results demonstrate that truncated intimin can be used as an anchor protein that mediates the translocation of various passenger proteins through the cytoplasmic and outer membranes of E. coli and their exposure on the cell surface. Intimin display may prove a useful tool for future protein translocation studies with interesting biological and biotechnological ramifications.
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Affiliation(s)
- A Wentzel
- Abteilung für Molekulare Genetik und Präparative Molekularbiologie, Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen, D-37077 Göttingen, Germany
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93
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Delahay RM, Frankel G, Knutton S. Intimate interactions of enteropathogenic Escherichia coli at the host cell surface. Curr Opin Infect Dis 2001; 14:559-65. [PMID: 11964876 DOI: 10.1097/00001432-200110000-00009] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Unlike many gastrointestinal pathogens, enteropathogenic Escherichia coli orchestrates the modulation of host cellular and immune responses from the exterior of the infected cell, chiefly via the secreted and translocated components of a type III secretion system. Close inspection of these enteropathogenic Escherichia coli proteins and the interactions they mediate provides an increasingly coherent picture of the pathogenic mechanisms that enteropathogenic Escherichia coli uses to exploit its host.
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Affiliation(s)
- R M Delahay
- Centre for Molecular Microbiology and Infection, Imperial College of Science, Technology and Medicine, London, UK.
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94
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Deora R, Bootsma HJ, Miller JF, Cotter PA. Diversity in the Bordetella virulence regulon: transcriptional control of a Bvg-intermediate phase gene. Mol Microbiol 2001; 40:669-83. [PMID: 11359572 DOI: 10.1046/j.1365-2958.2001.02415.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The BvgAS signal transduction system controls the expression of at least three distinct phenotypic phases that lie along a continuum of gene expression states. The Bvg+ phase is characterized by the expression of adhesins and toxins, whereas the Bvg- phase is characterized by motility in Bordetella bronchiseptica and the expression of vrg loci in Bordetella pertussis. The Bvg-intermediate (Bvgi) phase is characterized by the absence of Bvg-repressed phenotypes, the expression of some, but not all, Bvg-activated virulence factors and the presence of a recently discovered set of antigens and phenotypes that are unique to this phase. We report here the transcriptional regulation of bipA, the first-identified Bvgi phase gene. We have mapped the bipA promoter and identified numerous BvgA binding sites in the transcriptional control region. Based on these data, we present a model in which phase-dependent expression of bipA results from the spatial distribution and relative affinities of multiple BvgA binding sites relative to the start site of transcription.
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Affiliation(s)
- R Deora
- Department of Microbiology, Immunology and Molecular Genetics, and Molecular Biology Institute, UCLA School of Medicine, 10833 LeConte Ave., Los Angeles, CA 90095-1747, USA
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95
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Kresse AU, Guzmán CA, Ebel F. Modulation of host cell signalling by enteropathogenic and Shiga toxin-producing Escherichia coli. Int J Med Microbiol 2001; 291:277-85. [PMID: 11680788 DOI: 10.1078/1438-4221-00131] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The majority of Escherichia coli strains are harmless symbionts in the intestinal tract. However, there are several pathogenic forms, which are responsible for various diseases in humans and live stock. In this review we discuss the interactions between Shiga toxin-producing E. coli and enteropathogenic E. coli and their target host cells, describing their strategies to activate specific cellular signalling pathways which lead to subversion of critical physiological functions. We mainly concentrate on those pathogenic mechanisms that are dependent on a functional type III secretion system, but we also briefly discuss additional factors that contribute to the specific pathogenic profiles of Shiga toxin-producing E. coli and enreropathogenic E. coli.
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Affiliation(s)
- A U Kresse
- German Research Centre for Biotechnology (GBF), Braunschweig
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96
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Nölling J, Breton G, Omelchenko MV, Makarova KS, Zeng Q, Gibson R, Lee HM, Dubois J, Qiu D, Hitti J, Wolf YI, Tatusov RL, Sabathe F, Doucette-Stamm L, Soucaille P, Daly MJ, Bennett GN, Koonin EV, Smith DR. Genome sequence and comparative analysis of the solvent-producing bacterium Clostridium acetobutylicum. J Bacteriol 2001; 183:4823-38. [PMID: 11466286 PMCID: PMC99537 DOI: 10.1128/jb.183.16.4823-4838.2001] [Citation(s) in RCA: 636] [Impact Index Per Article: 27.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The genome sequence of the solvent-producing bacterium Clostridium acetobutylicum ATCC 824 has been determined by the shotgun approach. The genome consists of a 3.94-Mb chromosome and a 192-kb megaplasmid that contains the majority of genes responsible for solvent production. Comparison of C. acetobutylicum to Bacillus subtilis reveals significant local conservation of gene order, which has not been seen in comparisons of other genomes with similar, or, in some cases closer, phylogenetic proximity. This conservation allows the prediction of many previously undetected operons in both bacteria. However, the C. acetobutylicum genome also contains a significant number of predicted operons that are shared with distantly related bacteria and archaea but not with B. subtilis. Phylogenetic analysis is compatible with the dissemination of such operons by horizontal transfer. The enzymes of the solventogenesis pathway and of the cellulosome of C. acetobutylicum comprise a new set of metabolic capacities not previously represented in the collection of complete genomes. These enzymes show a complex pattern of evolutionary affinities, emphasizing the role of lateral gene exchange in the evolution of the unique metabolic profile of the bacterium. Many of the sporulation genes identified in B. subtilis are missing in C. acetobutylicum, which suggests major differences in the sporulation process. Thus, comparative analysis reveals both significant conservation of the genome organization and pronounced differences in many systems that reflect unique adaptive strategies of the two gram-positive bacteria.
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Affiliation(s)
- J Nölling
- GTC Sequencing Center, Genome Therapeutics Corporation, Waltham, Massachusetts 02453, USA
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97
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Affiliation(s)
- V T Lee
- Department of Microbiology & Immunology, UCLA School of Medicine, Los Angeles, California 90095, USA.
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98
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Daniell SJ, Delahay RM, Shaw RK, Hartland EL, Pallen MJ, Booy F, Ebel F, Knutton S, Frankel G. Coiled-coil domain of enteropathogenic Escherichia coli type III secreted protein EspD is involved in EspA filament-mediated cell attachment and hemolysis. Infect Immun 2001; 69:4055-64. [PMID: 11349076 PMCID: PMC98469 DOI: 10.1128/iai.69.6.4055-4064.2001] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Many animal and plant pathogens use type III secretion systems to secrete key virulence factors, some directly into the host cell cytosol. However, the basis for such protein translocation has yet to be fully elucidated for any type III secretion system. We have previously shown that in enteropathogenic and enterohemorrhagic Escherichia coli the type III secreted protein EspA is assembled into a filamentous organelle that attaches the bacterium to the plasma membrane of the host cell. Formation of EspA filaments is dependent on expression of another type III secreted protein, EspD. The carboxy terminus of EspD, a protein involved in formation of the translocation pore in the host cell membrane, is predicted to adopt a coiled-coil conformation with 99% probability. Here, we demonstrate EspD-EspD protein interaction using the yeast two-hybrid system and column overlays. Nonconservative triple amino acid substitutions of specific EspD carboxy-terminal residues generated an enteropathogenic E. coli mutant that was attenuated in its ability to induce attaching and effacing lesions on HEp-2 cells. Although the mutation had no effect on EspA filament biosynthesis, it also resulted in reduced binding to and reduced hemolysis of red blood cells. These results segregate, for the first time, functional domains of EspD that control EspA filament length from EspD-mediated cell attachment and pore formation.
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Affiliation(s)
- S J Daniell
- Department of Biochemistry, Imperial College of Science, Technology and Medicine, London SW7 2AZ, United Kingdom
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99
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Affiliation(s)
- T A Oelschlaeger
- Institut für Molekulare Infektionsbiologie, University of Würzburg, Germany.
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100
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Reece S, Simmons CP, Fitzhenry RJ, Matthews S, Phillips AD, Dougan G, Frankel G. Site-directed mutagenesis of intimin alpha modulates intimin-mediated tissue tropism and host specificity. Mol Microbiol 2001; 40:86-98. [PMID: 11298278 DOI: 10.1046/j.1365-2958.2001.02371.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The hallmark of enteropathogenic (EPEC) and enterohaemorrhagic (EHEC) Escherchia coli adhesion to host cells is intimate attachment leading to the formation of distinctive 'attaching and effacing' lesions. This event is mediated, in part, by binding of the bacterial adhesion molecule intimin to a second bacterial protein, Tir, delivered by a type III secretion system into the host cell plasma membrane. The receptor-binding activity of intimin is localized to the C-terminal 280 amino acids (Int280) and at least five distinct intimin types (alpha, beta, gamma, delta and epsilon) have been identified thus far. In addition to binding to Tir, intimin can also bind to a component encoded by the host. The consequence of latter intimin-binding activity may determine tissue tropism and host specificity. In this study we selected three amino acids in intimin, which are implicated in Tir binding, for site-directed mutagenesis. We used the yeast two-hybrid system and gel overlays to study intimin-Tir protein interaction. In addition, the biological consequences of the mutagenesis was tested using a number of infection models (cultured epithelial cells, human intestinal explants and a mouse model). We report that while an I237/897A substitution (positions numbered according to Int280alpha/whole intimin alpha) in intimin alpha did not have any affect on its biological activity, a T255/914A substitution attenuated intimin activity in vivo. In contrast, the mutation V252/911A affected tissue targeting in the human intestinal explant model and attenuated the biological activity of intimin in the mouse model. This study provides the first clues of the molecular basis of how intimin mediates tissue tropism and host specificity.
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Affiliation(s)
- S Reece
- Centre for Molecular Microbiology and Infection, Department of Biochemistry, Imperial College of Science, Technology and Medicine, London SW7 2AZ, UK
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