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Zupan J, Hackworth CA, Aguilar J, Ward D, Zambryski P. VirB1* promotes T-pilus formation in the vir-Type IV secretion system of Agrobacterium tumefaciens. J Bacteriol 2007; 189:6551-63. [PMID: 17631630 PMCID: PMC2045169 DOI: 10.1128/jb.00480-07] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The vir-type IV secretion system of Agrobacterium is assembled from 12 proteins encoded by the virB operon and virD4. VirB1 is one of the least-studied proteins encoded by the virB operon. Its N terminus is a lytic transglycosylase. The C-terminal third of the protein, VirB1*, is cleaved from VirB1 and secreted to the outside of the bacterial cell, suggesting an additional function. We show that both nopaline and octopine strains produce abundant amounts of VirB1* and perform detailed studies on nopaline VirB1*. Both domains are required for wild-type virulence. We show here that the nopaline type VirB1* is essential for the formation of the T pilus, a subassembly of the vir-T4SS composed of processed and cyclized VirB2 (major subunit) and VirB5 (minor subunit). A nopaline virB1 deletion strain does not produce T pili. Complementation with full-length VirB1 or C-terminal VirB1*, but not the N-terminal lytic transglycosylase domain, restores T pili containing VirB2 and VirB5. T-pilus preparations also contain extracellular VirB1*. Protein-protein interactions between VirB1* and VirB2 and VirB5 were detected in the yeast two-hybrid assay. We propose that VirB1 is a bifunctional protein required for virT4SS assembly. The N-terminal lytic transglycosylase domain provides localized lysis of the peptidoglycan cell wall to allow insertion of the T4SS. The C-terminal VirB1* promotes T-pilus assembly through protein-protein interactions with T-pilus subunits.
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Affiliation(s)
- John Zupan
- Department of Plant and Microbial Biology, Koshland Hall, University of California, Berkeley, CA 94720-3102, USA
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52
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Yu G, Snyder E, Boyle S, Crasta O, Czar M, Mane S, Purkayastha A, Sobral B, Setubal J. A versatile computational pipeline for bacterial genome annotation improvement and comparative analysis, with Brucella as a use case. Nucleic Acids Res 2007; 35:3953-62. [PMID: 17553834 PMCID: PMC1919506 DOI: 10.1093/nar/gkm377] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
We present a bacterial genome computational analysis pipeline, called GenVar. The pipeline, based on the program GeneWise, is designed to analyze an annotated genome and automatically identify missed gene calls and sequence variants such as genes with disrupted reading frames (split genes) and those with insertions and deletions (indels). For a given genome to be analyzed, GenVar relies on a database containing closely related genomes (such as other species or strains) as well as a few additional reference genomes. GenVar also helps identify gene disruptions probably caused by sequencing errors. We exemplify GenVar's capabilities by presenting results from the analysis of four Brucella genomes. Brucella is an important human pathogen and zoonotic agent. The analysis revealed hundreds of missed gene calls, new split genes and indels, several of which are species specific and hence provide valuable clues to the understanding of the genome basis of Brucella pathogenicity and host specificity.
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Affiliation(s)
- G.X. Yu
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA 24061, Department of Biology and Department of Computer Science, Boise State University, Boise, ID 83726 and Center for Molecular Medicine and Infectious Diseases, Virginia–Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061, USA
| | - E.E. Snyder
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA 24061, Department of Biology and Department of Computer Science, Boise State University, Boise, ID 83726 and Center for Molecular Medicine and Infectious Diseases, Virginia–Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061, USA
| | - S.M. Boyle
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA 24061, Department of Biology and Department of Computer Science, Boise State University, Boise, ID 83726 and Center for Molecular Medicine and Infectious Diseases, Virginia–Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061, USA
| | - O.R. Crasta
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA 24061, Department of Biology and Department of Computer Science, Boise State University, Boise, ID 83726 and Center for Molecular Medicine and Infectious Diseases, Virginia–Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061, USA
| | - M. Czar
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA 24061, Department of Biology and Department of Computer Science, Boise State University, Boise, ID 83726 and Center for Molecular Medicine and Infectious Diseases, Virginia–Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061, USA
| | - S.P. Mane
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA 24061, Department of Biology and Department of Computer Science, Boise State University, Boise, ID 83726 and Center for Molecular Medicine and Infectious Diseases, Virginia–Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061, USA
| | - A. Purkayastha
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA 24061, Department of Biology and Department of Computer Science, Boise State University, Boise, ID 83726 and Center for Molecular Medicine and Infectious Diseases, Virginia–Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061, USA
| | - B. Sobral
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA 24061, Department of Biology and Department of Computer Science, Boise State University, Boise, ID 83726 and Center for Molecular Medicine and Infectious Diseases, Virginia–Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061, USA
| | - J.C. Setubal
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA 24061, Department of Biology and Department of Computer Science, Boise State University, Boise, ID 83726 and Center for Molecular Medicine and Infectious Diseases, Virginia–Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061, USA
- *To whom correspondence should be addressed. +1 540 231 9464+1 540 231 2606
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Kohler PL, Hamilton HL, Cloud-Hansen K, Dillard JP. AtlA functions as a peptidoglycan lytic transglycosylase in the Neisseria gonorrhoeae type IV secretion system. J Bacteriol 2007; 189:5421-8. [PMID: 17526702 PMCID: PMC1951824 DOI: 10.1128/jb.00531-07] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Type IV secretion systems require peptidoglycan lytic transglycosylases for efficient secretion, but the function of these enzymes is not clear. The type IV secretion system gene cluster of Neisseria gonorrhoeae encodes two peptidoglycan transglycosylase homologues. One, LtgX, is similar to peptidoglycan transglycosylases from other type IV secretion systems. The other, AtlA, is similar to endolysins from bacteriophages and is not similar to any described type IV secretion component. We characterized the enzymatic function of AtlA in order to examine its role in the type IV secretion system. Purified AtlA was found to degrade macromolecular peptidoglycan and to produce 1,6-anhydro peptidoglycan monomers, characteristic of lytic transglycosylase activity. We found that AtlA can functionally replace the lambda endolysin to lyse Escherichia coli. In contrast, a sensitive measure of lysis demonstrated that AtlA does not lyse gonococci expressing it or gonococci cocultured with an AtlA-expressing strain. The gonococcal type IV secretion system secretes DNA during growth. A deletion of ltgX or a substitution in the putative active site of AtlA severely decreased DNA secretion. These results indicate that AtlA and LtgX are actively involved in type IV secretion and that AtlA is not involved in lysis of gonococci to release DNA. This is the first demonstration that a type IV secretion peptidoglycanase has lytic transglycosylase activity. These data show that AtlA plays a role in type IV secretion of DNA that requires peptidoglycan breakdown without cell lysis.
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Affiliation(s)
- Petra L Kohler
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
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54
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Baron C. VirB8: a conserved type IV secretion system assembly factor and drug target. Biochem Cell Biol 2007; 84:890-9. [PMID: 17215876 DOI: 10.1139/o06-148] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Type IV secretion systems are used by many gram-negative bacteria for the translocation of macromolecules (proteins, DNA, or DNA-protein complexes) across the cell envelope. Among them are many pathogens for which type IV secretion systems are essential virulence factors. Type IV secretion systems comprise 8-12 conserved proteins, which assemble into a complex spanning the inner and the outer membrane, and many assemble extracellular appendages, such as pili, which initiate contact with host and recipient cells followed by substrate translocation. VirB8 is an essential assembly factor for all type IV secretion systems. Biochemical, cell biological, genetic, and yeast two-hybrid analyses showed that VirB8 undergoes multiple interactions with other type IV secretion system components and that it directs polar assembly of the membrane-spanning complex in the model organism Agrobacterium tumefaciens. The availability of the VirB8 X-ray structure has enabled a detailed structure-function analysis, which identified sites for the binding of VirB4 and VirB10 and for self-interaction. Due to its multiple interactions, VirB8 is an excellent model for the analysis of assembly factors of multiprotein complexes. In addition, VirB8 is a possible target for drugs that target its protein-protein interactions, which would disarm bacteria by depriving them of their essential virulence functions.
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Affiliation(s)
- Christian Baron
- McMaster University, Department of Biology and Antimicrobial Research Centre, 1280 Main St. West, Hamilton, ON LS8 4K1, Canada.
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55
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Bayliss R, Harris R, Coutte L, Monier A, Fronzes R, Christie PJ, Driscoll PC, Waksman G. NMR structure of a complex between the VirB9/VirB7 interaction domains of the pKM101 type IV secretion system. Proc Natl Acad Sci U S A 2007; 104:1673-8. [PMID: 17244707 PMCID: PMC1785264 DOI: 10.1073/pnas.0609535104] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2006] [Indexed: 11/18/2022] Open
Abstract
Type IV secretion (T4S) systems translocate DNA and protein effectors through the double membrane of Gram-negative bacteria. The paradigmatic T4S system in Agrobacterium tumefaciens is assembled from 11 VirB subunits and VirD4. Two subunits, VirB9 and VirB7, form an important stabilizing complex in the outer membrane. We describe here the NMR structure of a complex between the C-terminal domain of the VirB9 homolog TraO (TraO(CT)), bound to VirB7-like TraN from plasmid pKM101. TraO(CT) forms a beta-sandwich around which TraN winds. Structure-based mutations in VirB7 and VirB9 of A. tumefaciens show that the heterodimer interface is conserved. Opposite this interface, the TraO structure shows a protruding three-stranded beta-appendage, and here, we supply evidence that the corresponding region of VirB9 of A. tumefaciens inserts in the membrane and protrudes extracellularly. This complex structure elucidates the molecular basis for the interaction between two essential components of a T4S system.
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Affiliation(s)
- Richard Bayliss
- *Institute of Structural Molecular Biology, University College London/Birkbeck, Malet Street, London WC1E 7HX, United Kingdom
| | - Richard Harris
- Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom; and
| | - Loic Coutte
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, 6431 Fannin Street, Houston, TX 77030
| | - Amy Monier
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, 6431 Fannin Street, Houston, TX 77030
| | - Remi Fronzes
- *Institute of Structural Molecular Biology, University College London/Birkbeck, Malet Street, London WC1E 7HX, United Kingdom
| | - Peter J. Christie
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, 6431 Fannin Street, Houston, TX 77030
| | - Paul C. Driscoll
- *Institute of Structural Molecular Biology, University College London/Birkbeck, Malet Street, London WC1E 7HX, United Kingdom
- Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom; and
| | - Gabriel Waksman
- *Institute of Structural Molecular Biology, University College London/Birkbeck, Malet Street, London WC1E 7HX, United Kingdom
- Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom; and
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56
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Graham RLJ, Pollock CE, O'Loughlin SN, Ternan NG, Weatherly DB, Jackson PJ, Tarleton RL, McMullan G. Multidimensional proteomic analysis of the soluble subproteome of the emerging nosocomial pathogen Ochrobactrum anthropi. J Proteome Res 2007; 5:3145-53. [PMID: 17081066 DOI: 10.1021/pr060293g] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report the first large-scale gel-free proteomic analysis of the soluble subproteome of the emerging pathogen Ochrobactrum anthropi. Utilizing our robust offline multidimensional protein identification protocol, a total of 57 280 peptides were initially identified utilizing automated MS/MS analysis software. We describe our investigation of the heuristic protein validation tool PROVALT and demonstrate its ability to increase the speed and accuracy of the curation process of large-scale proteomic datasets. PROVALT reduced our peptide list to 8517 identified peptides and further manual curation of these peptides led to a final list of 984 uniquely identified peptides that resulted in the positive identification of 249 proteins. These identified proteins were functionally classified and physiochemically characterized. A variety of typical "housekeeping" functions identified within the proteome included nucleic acid, amino and fatty acid anabolism and catabolism, glycolysis, TCA cycle, and pyruvate and selenoamino acid metabolism. In addition, a number of potential virulence factors of relevance to both plant and human disease were identified.
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Affiliation(s)
- Robert Leslie James Graham
- School of Biomedical Sciences, University of Ulster, Coleraine, County Londonderry, BT52 1SA, United Kingdom.
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57
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Hare S, Bayliss R, Baron C, Waksman G. A large domain swap in the VirB11 ATPase of Brucella suis leaves the hexameric assembly intact. J Mol Biol 2006; 360:56-66. [PMID: 16730027 DOI: 10.1016/j.jmb.2006.04.060] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2006] [Revised: 04/25/2006] [Accepted: 04/26/2006] [Indexed: 11/28/2022]
Abstract
VirB11 ATPases are hexameric assemblies that power type IV secretion systems in bacteria. The hexamer of Brucella suis VirB11 (BsB11), like that of the Helicobacter pylori VirB11 (Hp0525), consists of a double ring structure formed by the N-terminal and C-terminal domains of each monomer. However, the monomer differs dramatically from that of Hp0525 by a large domain swap that leaves the hexameric assembly intact but profoundly alters the nucleotide-binding site and the interface between subunits.
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Affiliation(s)
- Stephen Hare
- School of Crystallography, Birkbeck College, Malet Street, London, WC1E 7HX, UK
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58
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Paschos A, Patey G, Sivanesan D, Gao C, Bayliss R, Waksman G, O'Callaghan D, Baron C. Dimerization and interactions of Brucella suis VirB8 with VirB4 and VirB10 are required for its biological activity. Proc Natl Acad Sci U S A 2006; 103:7252-7. [PMID: 16648257 PMCID: PMC1464329 DOI: 10.1073/pnas.0600862103] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
VirB8-like proteins are essential components of type IV secretion systems, bacterial virulence factors that mediate the translocation of effector molecules from many bacterial pathogens into eukaryotic cells. Based on cell biological, genetic, and x-ray crystallographic data, VirB8 was proposed to undergo multiple protein-protein interactions to mediate assembly of the translocation machinery. Here we report the results of a structure-function analysis of the periplasmic domain of VirB8 from the mammalian pathogen Brucella suis, which identifies amino acid residues required for three protein-protein interactions. VirB8 variants changed at residues proposed to be involved in dimerization, and protein-protein interactions were purified and characterized in vitro and in vivo. Changes at M102, Y105, and E214 affected the self-association as measured by analytical ultracentrifugation and gel filtration. The interaction with B. suis VirB10 was reduced by changes at T201, and change at R230 inhibited the interaction with VirB4 in vitro. The in vivo functionality of VirB8 variants was determined by complementation of growth in macrophages by a B. suis virB8 mutant and by using a heterologous assay of type IV secretion system assembly in Agrobacterium tumefaciens. Changes at Y105, T201, R230, and at several other residues impaired the in vivo function of VirB8, suggesting that we have identified interaction sites of relevance in the natural biological context.
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Affiliation(s)
- Athanasios Paschos
- *Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON, Canada L8S 4K1
| | - Gilles Patey
- Institut National de la Santé et de la Recherche Médicale U431, Faculté de Médecine, Avenue Kennedy, F-30900 Nîmes, France
| | - Durga Sivanesan
- *Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON, Canada L8S 4K1
| | - Chan Gao
- *Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON, Canada L8S 4K1
| | - Richard Bayliss
- School of Crystallography, Birkbeck College, Malet Street, London WC1E 7HX, United Kingdom
- Institute of Structural Molecular Biology, University College London/Birkbeck, Malet Street, London WC1E 7HX, United Kingdom
| | - Gabriel Waksman
- School of Crystallography, Birkbeck College, Malet Street, London WC1E 7HX, United Kingdom
- Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom; and
- Institute of Structural Molecular Biology, University College London/Birkbeck, Malet Street, London WC1E 7HX, United Kingdom
| | - David O'Callaghan
- Institut National de la Santé et de la Recherche Médicale U431, Faculté de Médecine, Avenue Kennedy, F-30900 Nîmes, France
| | - Christian Baron
- *Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON, Canada L8S 4K1
- **To whom correspondence should be addressed. E-mail:
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59
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Carle A, Höppner C, Ahmed Aly K, Yuan Q, den Dulk-Ras A, Vergunst A, O'Callaghan D, Baron C. The Brucella suis type IV secretion system assembles in the cell envelope of the heterologous host Agrobacterium tumefaciens and increases IncQ plasmid pLS1 recipient competence. Infect Immun 2006; 74:108-17. [PMID: 16368963 PMCID: PMC1346655 DOI: 10.1128/iai.74.1.108-117.2006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pathogenic Brucella species replicate within mammalian cells, and their type IV secretion system is essential for intracellular survival and replication. The options for biochemical studies on the Brucella secretion system are limited due to the rigidity of the cells and biosafety concerns, which preclude large-scale cell culture and fractionation. To overcome these problems, we heterologously expressed the Brucella suis virB operon in the closely related alpha(2)-proteobacterium Agrobacterium tumefaciens and showed that the VirB proteins assembled into a complex. Eight of the twelve VirB proteins were detected in the membranes of the heterologous host with specific antisera. Cross-linking indicated protein-protein interactions similar to those in other type IV secretion systems, and the results of immunofluorescence analysis supported the formation of VirB protein complexes in the cell envelope. Production of a subset of the B. suis VirB proteins (VirB3-VirB12) in A. tumefaciens strongly increased its ability to receive IncQ plasmid pLS1 in conjugation experiments, and production of VirB1 further enhanced the conjugation efficiency. Plasmid recipient competence correlated with periplasmic leakage and the detergent sensitivity of A. tumefaciens, suggesting a weakening of the cell envelope. Heterologous expression thus permits biochemical characterization of B. suis type IV secretion system assembly.
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Affiliation(s)
- Anna Carle
- McMaster University, Department of Biology, 1280 Main Street West, Hamilton, Ontario LS8 4K1, Canada
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60
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Baron C. From bioremediation to biowarfare: On the impact and mechanism of type IV secretion systems. FEMS Microbiol Lett 2005; 253:163-70. [PMID: 16239080 DOI: 10.1016/j.femsle.2005.09.030] [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] [Received: 08/08/2005] [Revised: 09/21/2005] [Accepted: 09/21/2005] [Indexed: 11/28/2022] Open
Abstract
Type IV secretion systems are employed by a wide variety of Gram-negative microorganisms for the translocation of macromolecules across the cell envelope. The translocated substrates (proteins, protein-DNA complexes and DNA) are as diverse as the organisms on the donor and recipient side of the translocation process. Over the course of evolution, these macromolecular transporters were adapted to many different purposes, but their basic mechanism was conserved. They impact human life in various ways, as there are driving forces of horizontal gene transfer, which spreads biodegradative capabilities of environmental bacteria as well as antibiotic resistance of pathogens in hospitals. Also, they translocate toxins and other effectors, which have an effect on host cell metabolism and are essential for the virulence of bacterial pathogens. We here present recent developments of research on the mechanism of type IV secretion focusing on the energetization of transport and assembly processes, formation of the translocation channel and of surface-exposed pili, which initiate host cell interactions.
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Affiliation(s)
- Christian Baron
- McMaster University, Department of Biology, 1280 Main Street, West Hamilton, ON, Canada.
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61
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Zahrl D, Wagner M, Bischof K, Bayer M, Zavecz B, Beranek A, Ruckenstuhl C, Zarfel GE, Koraimann G. Peptidoglycan degradation by specialized lytic transglycosylases associated with type III and type IV secretion systems. Microbiology (Reading) 2005; 151:3455-3467. [PMID: 16272370 DOI: 10.1099/mic.0.28141-0] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Specialized lytic transglycosylases are muramidases capable of locally degrading the peptidoglycan meshwork of Gram-negative bacteria. Specialized lytic transglycosylase genes are present in clusters encoding diverse macromolecular transport systems. This paper reports the analysis of selected members of the specialized lytic transglycosylase family from type III and type IV secretion systems. These proteins were analysedin vivoby assaying their ability to complement the DNA transfer defect of the conjugative F-like plasmid R1-16 lacking a functional P19 protein, the specialized lytic transglycosylase of this type IV secretion system. Heterologous complementation was accomplished using IpgF from the plasmid-encoded type III secretion system ofShigella sonneiand TrbN from the type IV secretion system of the conjugative plasmid RP4. In contrast, neither VirB1 proteins (Agrobacterium tumefaciens,Brucella suis) nor IagB (Salmonella enterica) could functionally replace P19.In vitro, IpgF, IagB, both VirB1 proteins, HP0523 (Helicobacter pylori) and P19 displayed peptidoglycanase activity in zymogram analyses. Using an established test system and a newly developed assay it was shown that IpgF degraded peptidoglycan in solution. IpgF was active only after removal of the chaperonin GroEL, which co-purified with IpgF and inhibited its enzymic activity. A mutant IpgF protein in which the predicted catalytic amino acid, Glu42, was replaced by Gln, was completely inactive. IpgF-catalysed peptidoglycan degradation was optimal at pH 6 and was inhibited by the lytic transglycosylase inhibitors hexa-N-acetylchitohexaose and bulgecin A.
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Affiliation(s)
- Doris Zahrl
- Institut für Molekulare Biowissenschaften (IMB), Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria
| | - Maria Wagner
- Institut für Molekulare Biowissenschaften (IMB), Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria
| | - Karin Bischof
- Institut für Molekulare Biowissenschaften (IMB), Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria
| | - Michaela Bayer
- Institut für Molekulare Biowissenschaften (IMB), Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria
| | - Barbara Zavecz
- Institut für Molekulare Biowissenschaften (IMB), Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria
| | - Andreas Beranek
- Institut für Molekulare Biowissenschaften (IMB), Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria
| | - Christoph Ruckenstuhl
- Institut für Molekulare Biowissenschaften (IMB), Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria
| | - Gernot E Zarfel
- Institut für Molekulare Biowissenschaften (IMB), Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria
| | - Günther Koraimann
- Institut für Molekulare Biowissenschaften (IMB), Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010 Graz, Austria
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