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Domain 4:

Synthesis and Processing of Macromolecules

The Mosaic Type IV Secretion Systems

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  • Author: Peter J. Christie1
  • Editors: Susan T. Lovett2, Harris D. Bernstein3
  • VIEW AFFILIATIONS HIDE AFFILIATIONS
    Affiliations: 1: Department of Microbiology and Molecular Genetics, The University of Texas Medical School at Houston, Houston, TX 77030; 2: Brandeis University, Waltham, MA; 3: National Institutes of Health, Bethesda, MD
  • Received 01 December 2015 Accepted 05 May 2016 Published 04 August 2016
  • Address correspondence to Peter J. Christie, Peter.J.Christie@uth.tmc.edu
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  • Abstract:

    and other Gram-negative and -positive bacteria employ type IV secretion systems (T4SSs) to translocate DNA and protein substrates, generally by contact-dependent mechanisms, to other cells. The T4SSs functionally encompass two major subfamilies, the conjugation systems and the effector translocators. The conjugation systems are responsible for interbacterial transfer of antibiotic resistance genes, virulence determinants, and genes encoding other traits of potential benefit to the bacterial host. The effector translocators are used by many Gram-negative pathogens for delivery of potentially hundreds of virulence proteins termed effectors to eukaryotic cells during infection. In and other species of , T4SSs identified to date function exclusively in conjugative DNA transfer. In these species, the plasmid-encoded systems can be classified as the P, F, and I types. The P-type systems are the simplest in terms of subunit composition and architecture, and members of this subfamily share features in common with the paradigmatic VirB/VirD4 T4SS. This review will summarize our current knowledge of the systems and the P-type system, with emphasis on the structural diversity of the T4SSs. Ancestral P-, F-, and I-type systems were adapted throughout evolution to yield the extant effector translocators, and information about well-characterized effector translocators also is included to further illustrate the adaptive and mosaic nature of these highly versatile machines.

  • Citation: Christie P. 2016. The Mosaic Type IV Secretion Systems, EcoSal Plus 2016; doi:10.1128/ecosalplus.ESP-0020-2015

Key Concept Ranking

Bacterial Proteins
0.62644565
Mobile Genetic Elements
0.5922244
Bacterial Mobile Genetic Elements
0.45909563
Type VI Secretion System
0.44990832
Type II Secretion System
0.44269305
0.62644565

References

1. Cascales E, Christie PJ. 2003. The versatile bacterial type IV secretion systems. Nat Rev Microbiol 1:137–149. [PubMed][CrossRef]
2. Alvarez-Martinez CE, Christie PJ. 2009. Biological diversity of prokaryotic type IV secretion systems. Microbiol Mol Biol Rev 73:775–808. [PubMed][CrossRef]
3. Cabezón E, Ripoll-Rozada J, Peña A, de la Cruz F, Arechaga I. 2015. Towards an integrated model of bacterial conjugation. FEMS Microbiol Rev 39:81–95. [PubMed]
4. Juhas M. 2015. Horizontal gene transfer in human pathogens. Crit Rev Microbiol 41:101–108. [PubMed][CrossRef]
5. Guglielmini J, de la Cruz F, Rocha EP. 2013. Evolution of conjugation and type IV secretion systems. Mol Biol Evol 30:315–331. [PubMed][CrossRef]
6. Christie PJ, Whitaker N, González-Rivera C. 2014. Mechanism and structure of the bacterial type IV secretion systems. Biochim Biophys Acta 1843:1578–1591. [PubMed][CrossRef]
7. Chandran Darbari V, Waksman G. 2015. Structural biology of bacterial type IV secretion systems. Annu Rev Biochem 84:603–629. [PubMed][CrossRef]
8. Bhatty M, Laverde Gomez JA, Christie PJ. 2013. The expanding bacterial type IV secretion lexicon. Res Microbiol 164:620–639. [PubMed][CrossRef]
9. Kubori T, Nagai H. 2016. The Type IVB secretion system: an enigmatic chimera. Curr Opin Microbiol 29:22–29. [PubMed][CrossRef]
10. Asrat S, Davis KM, Isberg RR. 2015. Modulation of the host innate immune and inflammatory response by translocated bacterial proteins. Cell Microbiol 17:785–795. [PubMed][CrossRef]
11. Locht C, Coutte L, Mielcarek N. 2011. The ins and outs of pertussis toxin. FEBS J 278:4668–4682. [PubMed][CrossRef]
12. Ramsey ME, Woodhams KL, Dillard JP. 2011. The gonococcal genetic island and type IV secretion in the pathogenic Neisseria. Front Microbiol 2:61. [PubMed][CrossRef]
13. Stingl K, Müller S, Scheidgen-Kleyboldt G, Clausen M, Maier B. 2010. Composite system mediates two-step DNA uptake into Helicobacter pylori. Proc Natl Acad Sci USA 107:1184–1189. [PubMed][CrossRef]
14. Arutyunov D, Frost LS. 2013. F conjugation: back to the beginning. Plasmid 70:18–32. [PubMed][CrossRef]
15. Clarke M, Maddera L, Harris RL, Silverman PM. 2008. F-pili dynamics by live-cell imaging. Proc Natl Acad Sci USA 105:17978–17981. [PubMed][CrossRef]
16. Silverman PM, Clarke MB. 2010. New insights into F-pilus structure, dynamics, and function. Integr Biol Camb 2:25–31. [PubMed][CrossRef]
17. Christie PJ, Atmakuri K, Krishnamoorthy V, Jakubowski S, Cascales E. 2005. Biogenesis, architecture, and function of bacterial type IV secretion systems. Annu Rev Microbiol 59:451–485. [PubMed][CrossRef]
18. Costa TR, Felisberto-Rodrigues C, Meir A, Prevost MS, Redzej A, Trokter M, Waksman G. 2015. Secretion systems in Gram-negative bacteria: structural and mechanistic insights. Nat Rev Microbiol 13:343–359. [PubMed][CrossRef]
19. Sampei G, Furuya N, Tachibana K, Saitou Y, Suzuki T, Mizobuchi K, Komano T. 2010. Complete genome sequence of the incompatibility group I1 plasmid R64. Plasmid 64:92–103. [PubMed][CrossRef]
20. Nagai H, Kubori T. 2011. Type IVB secretion systems of Legionella and other Gram-negative bacteria. Front Microbiol 2:136. doi:10.3389/fmicb.2011.00136. [PubMed][CrossRef]
21. Christie PJ. 2004. Type IV secretion: the Agrobacterium VirB/D4 and related conjugation systems. Biochim Biophys Acta 1694:219–234. [PubMed][CrossRef]
22. Lawley TD, Klimke WA, Gubbins MJ, Frost LS. 2003. F factor conjugation is a true type IV secretion system. FEMS Microbiol Lett 224:1–15. [PubMed][CrossRef]
23. Cascales E, Christie PJ. 2004. Definition of a bacterial type IV secretion pathway for a DNA substrate. Science 304:1170–1173. [PubMed][CrossRef]
24. Fronzes R, Schäfer E, Wang L, Saibil HR, Orlova EV, Waksman G. 2009. Structure of a type IV secretion system core complex. Science 323:266–268. [PubMed][CrossRef]
25. Chandran V, Fronzes R, Duquerroy S, Cronin N, Navaza J, Waksman G. 2009. Structure of the outer membrane complex of a type IV secretion system. Nature 462:1011–1015. [PubMed][CrossRef]
26. Low HH, Gubellini F, Rivera-Calzada A, Braun N, Connery S, Dujeancourt A, Lu F, Redzej A, Fronzes R, Orlova EV, Waksman G. 2014. Structure of a type IV secretion system. Nature 508:550–553. [PubMed][CrossRef]
27. Trokter M, Felisberto-Rodrigues C, Christie PJ, Waksman G. 2014. Recent advances in the structural and molecular biology of type IV secretion systems. Curr Opin Struct Biol 27:16–23. [PubMed][CrossRef]
28. Zechner EL, Lang S, Schildbach JF. 2012. Assembly and mechanisms of bacterial type IV secretion machines. Philos Trans R Soc Lond B Biol Sci 367:1073–1087. [PubMed][CrossRef]
29. Mihajlovic S, Lang S, Sut MV, Strohmaier H, Gruber CJ, Koraimann G, Cabezón E, Moncalián G, de la Cruz F, Zechner EL. 2009. Plasmid R1 conjugative DNA processing is regulated at the coupling protein interface. J Bacteriol 191:6877–6887. [PubMed][CrossRef]
30. Sut MV, Mihajlovic S, Lang S, Gruber CJ, Zechner EL. 2009. Protein and DNA effectors control the TraI conjugative helicase of plasmid R1. J Bacteriol 191:6888–6899. [PubMed][CrossRef]
31. Vincent CD, Friedman JR, Jeong KC, Sutherland MC, Vogel JP. 2012. Identification of the DotL coupling protein subcomplex of the Legionella Dot/Icm type IV secretion system. Mol Microbiol 85:378–391. [PubMed][CrossRef]
32. Lang S, Gruber K, Mihajlovic S, Arnold R, Gruber CJ, Steinlechner S, Jehl MA, Rattei T, Fröhlich KU, Zechner EL. 2010. Molecular recognition determinants for type IV secretion of diverse families of conjugative relaxases. Mol Microbiol 78:1539–1555. [PubMed][CrossRef]
33. Redzej A, Ilangovan A, Lang S, Gruber CJ, Topf M, Zangger K, Zechner EL, Waksman G. 2013. Structure of a translocation signal domain mediating conjugative transfer by type IV secretion systems. Mol Microbiol 89:324–333. [PubMed][CrossRef]
34. Parker C, Meyer RJ. 2007. The R1162 relaxase/primase contains two, type IV transport signals that require the small plasmid protein MobB. Mol Microbiol 66:252–261. [PubMed][CrossRef]
35. Alperi A, Larrea D, Fernández-González E, Dehio C, Zechner EL, Llosa M. 2013. A translocation motif in relaxase TrwC specifically affects recruitment by its conjugative type IV secretion system. J Bacteriol 195:4999–5006. [PubMed][CrossRef]
36. Meyer R. 2015. Mapping type IV secretion signals on the primase encoded by the broad-host-range plasmid R1162 (RSF1010). J Bacteriol 197:3245–3254. [PubMed][CrossRef]
37. Vergunst AC, Schrammeijer B, den Dulk-Ras A, de Vlaam CM, Regensburg-Tuïnk TJ, Hooykaas PJ. 2000. VirB/D4-dependent protein translocation from Agrobacterium into plant cells. Science 290:979–982. [PubMed][CrossRef]
38. Vergunst AC, van Lier MC, den Dulk-Ras A, Stüve TA, Ouwehand A, Hooykaas PJ. 2005. Positive charge is an important feature of the C-terminal transport signal of the VirB/D4-translocated proteins of Agrobacterium. Proc Natl Acad Sci USA 102:832–837. [PubMed][CrossRef]
39. Cabezón E, Sastre JI, de la Cruz F. 1997. Genetic evidence of a coupling role for the TraG protein family in bacterial conjugation. Mol Gen Genet 254:400–406. [PubMed][CrossRef]
40. Schröder G, Lanka E. 2003. TraG-like proteins of type IV secretion systems: functional dissection of the multiple activities of TraG (RP4) and TrwB (R388). J Bacteriol 185:4371–4381. [PubMed][CrossRef]
41. Gomis-Rüth FX, Moncalián G, Pérez-Luque R, González A, Cabezón E, de la Cruz F, Coll M. 2001. The bacterial conjugation protein TrwB resembles ring helicases and F1-ATPase. Nature 409:637–641. [PubMed][CrossRef]
42. Hormaeche I, Alkorta I, Moro F, Valpuesta JM, Goni FM, De La Cruz F. 2002. Purification and properties of TrwB, a hexameric, ATP-binding integral membrane protein essential for R388 plasmid conjugation. J Biol Chem 277:46456–46462. [PubMed][CrossRef]
43. Gomis-Rüth FX, Coll M. 2001. Structure of TrwB, a gatekeeper in bacterial conjugation. Int J Biochem Cell Biol 33:839–843. [PubMed][CrossRef]
44. Schröder G, Krause S, Zechner EL, Traxler B, Yeo HJ, Lurz R, Waksman G, Lanka E. 2002. TraG-like proteins of DNA transfer systems and of the Helicobacter pylori type IV secretion system: inner membrane gate for exported substrates? J Bacteriol 184:2767–2779. [PubMed][CrossRef]
45. de Paz HD, Larrea D, Zunzunegui S, Dehio C, de la Cruz F, Llosa M. 2010. Functional dissection of the conjugative coupling protein TrwB. J Bacteriol 192:2655–2669. [PubMed][CrossRef]
46. Whitaker N, Chen Y, Jakubowski SJ, Sarkar MK, Li F, Christie PJ. 2015. The all-alpha domains of coupling proteins from the Agrobacterium tumefaciens VirB/VirD4 and Enterococcus faecalis pCF10-encoded type IV secretion systems confer specificity to binding of cognate DNA substrates. J Bacteriol 197:2335–2349. [PubMed][CrossRef]
47. van Kregten M, Lindhout BI, Hooykaas PJ, van der Zaal BJ. 2009. Agrobacterium-mediated T-DNA transfer and integration by minimal VirD2 consisting of the relaxase domain and a type IV secretion system translocation signal. Mol Plant Microbe Interact 22:1356–1365. [PubMed][CrossRef]
48. Atmakuri K, Cascales E, Burton OT, Banta LM, Christie PJ. 2007. Agrobacterium ParA/MinD-like VirC1 spatially coordinates early conjugative DNA transfer reactions. EMBO J 26:2540–2551. [PubMed][CrossRef]
49. Cascales E, Atmakuri K, Sarkar MK, Christie PJ. 2013. DNA substrate-induced activation of the Agrobacterium VirB/VirD4 type IV secretion system. J Bacteriol 195:2691–2704. [PubMed][CrossRef]
50. Sastre JI, Cabezón E, de la Cruz F. 1998. The carboxyl terminus of protein TraD adds specificity and efficiency to F-plasmid conjugative transfer. J Bacteriol 180:6039–6042. [PubMed]
51. Beranek A, Zettl M, Lorenzoni K, Schauer A, Manhart M, Koraimann G. 2004. Thirty-eight C-terminal amino acids of the coupling protein TraD of the F-like conjugative resistance plasmid R1 are required and sufficient to confer binding to the substrate selector protein TraM. J Bacteriol 186:6999–7006. [PubMed][CrossRef]
52. Lu J, Wong JJ, Edwards RA, Manchak J, Frost LS, Glover JN. 2008. Structural basis of specific TraD-TraM recognition during F plasmid-mediated bacterial conjugation. Mol Microbiol 70:89–99. [PubMed][CrossRef]
53. Lu J, Frost LS. 2005. Mutations in the C-terminal region of TraM provide evidence for in vivo TraM-TraD interactions during F-plasmid conjugation. J Bacteriol 187:4767–4773. [PubMed][CrossRef]
54. Atmakuri K, Cascales E, Christie PJ. 2004. Energetic components VirD4, VirB11 and VirB4 mediate early DNA transfer reactions required for bacterial type IV secretion. Mol Microbiol 54:1199–1211. [PubMed][CrossRef]
55. Llosa M, Zunzunegui S, de la Cruz F. 2003. Conjugative coupling proteins interact with cognate and heterologous VirB10-like proteins while exhibiting specificity for cognate relaxosomes. Proc Natl Acad Sci USA 100:10465–10470. [PubMed][CrossRef]
56. de Paz HD, Sangari FJ, Bolland S, García-Lobo JM, Dehio C, de la Cruz F, Llosa M. 2005. Functional interactions between type IV secretion systems involved in DNA transfer and virulence. Microbiology 151:3505–3516. [PubMed][CrossRef]
57. Tato I, Zunzunegui S, de la Cruz F, Cabezon E. 2005. TrwB, the coupling protein involved in DNA transport during bacterial conjugation, is a DNA-dependent ATPase. Proc Natl Acad Sci USA 102:8156–8161. [PubMed][CrossRef]
58. Tato I, Matilla I, Arechaga I, Zunzunegui S, de la Cruz F, Cabezon E. 2007. The ATPase activity of the DNA transporter TrwB is modulated by protein TrwA: implications for a common assembly mechanism of DNA translocating motors. J Biol Chem 282:25569–25576. [PubMed][CrossRef]
59. Ripoll-Rozada J, Zunzunegui S, de la Cruz F, Arechaga I, Cabezón E. 2013. Functional interactions of VirB11 traffic ATPases with VirB4 and VirD4 molecular motors in type IV secretion systems. J Bacteriol 195:4195–4201. [PubMed][CrossRef]
60. Berger BR, Christie PJ. 1994. Genetic complementation analysis of the Agrobacterium tumefaciens virB operon: virB2 through virB11 are essential virulence genes. J Bacteriol 176:3646–3660. [PubMed]
61. Haase J, Lurz R, Grahn AM, Bamford DH, Lanka E. 1995. Bacterial conjugation mediated by plasmid RP4: RSF1010 mobilization, donor-specific phage propagation, and pilus production require the same Tra2 core components of a proposed DNA transport complex. J Bacteriol 177:4779–4791. [PubMed]
62. Sagulenko E, Sagulenko V, Chen J, Christie PJ. 2001. Role of Agrobacterium VirB11 ATPase in T-pilus assembly and substrate selection. J Bacteriol 183:5813–5825. [PubMed][CrossRef]
63. Savvides SN, Yeo HJ, Beck MR, Blaesing F, Lurz R, Lanka E, Buhrdorf R, Fischer W, Haas R, Waksman G. 2003. VirB11 ATPases are dynamic hexameric assemblies: new insights into bacterial type IV secretion. EMBO J 22:1969–1980. [PubMed][CrossRef]
64. Hare S, Bayliss R, Baron C, Waksman G. 2006. A large domain swap in the VirB11 ATPase of Brucella suis leaves the hexameric assembly intact. J Mol Biol 360:56–66. [PubMed][CrossRef]
65. Savvides SN. 2007. Secretion superfamily ATPases swing big. Structure 15:255–257. [PubMed][CrossRef]
66. Akeda Y, Galán JE. 2005. Chaperone release and unfolding of substrates in type III secretion. Nature 437:911–915. [PubMed][CrossRef]
67. Middleton R, Sjölander K, Krishnamurthy N, Foley J, Zambryski P. 2005. Predicted hexameric structure of the Agrobacterium VirB4 C terminus suggests VirB4 acts as a docking site during type IV secretion. Proc Natl Acad Sci USA 102:1685–1690. [PubMed][CrossRef]
68. Yuan Q, Carle A, Gao C, Sivanesan D, Aly KA, Höppner C, Krall L, Domke N, Baron C. 2005. Identification of the VirB4-VirB8-VirB5-VirB2 pilus assembly sequence of type IV secretion systems. J Biol Chem 280:26349–26359. [PubMed][CrossRef]
69. Li F, Alvarez-Martinez C, Chen Y, Choi KJ, Yeo HJ, Christie PJ. 2012. Enterococcus faecalis PrgJ, a VirB4-like ATPase, mediates pCF10 conjugative transfer through substrate binding. J Bacteriol 194:4041–4051. [PubMed][CrossRef]
70. Peña A, Matilla I, Martín-Benito J, Valpuesta JM, Carrascosa JL, de la Cruz F, Cabezón E, Arechaga I. 2012. The hexameric structure of a conjugative VirB4 protein ATPase provides new insights for a functional and phylogenetic relationship with DNA translocases. J Biol Chem 287:39925–39932. [PubMed][CrossRef]
71. Durand E, Oomen C, Waksman G. 2010. Biochemical dissection of the ATPase TraB, the VirB4 homologue of the Escherichia coli pKM101 conjugation machinery. J Bacteriol 192:2315–2323. [PubMed][CrossRef]
72. Jakubowski SJ, Krishnamoorthy V, Cascales E, Christie PJ. 2004. Agrobacterium tumefaciens VirB6 domains direct the ordered export of a DNA substrate through a type IV secretion system. J Mol Biol 341:961–977. [PubMed][CrossRef]
73. Rees CE, Wilkins BM. 1989. Transfer of Tra proteins into the recipient cell during bacterial conjugation mediated by plasmid ColIb-P9. J Bacteriol 171:3152–3157. [PubMed]
74. Rees CED, Wilkins BM. 1990. Protein transfer into the recipient cell during bacterial conjugation: studies with F and RP4. Mol Microbiol 4:1199–1205. [PubMed][CrossRef]
75. Ninio S, Roy CR. 2007. Effector proteins translocated by Legionella pneumophila: strength in numbers. Trends Microbiol 15:372–380. [PubMed][CrossRef]
76. Zhu W, Banga S, Tan Y, Zheng C, Stephenson R, Gately J, Luo ZQ. 2011. Comprehensive identification of protein substrates of the Dot/Icm type IV transporter of Legionella pneumophila. PLoS One 6:e17638. doi:10.1371/journal.pone.0017638. [CrossRef]
77. Kumar RB, Das A. 2001. Functional analysis of the Agrobacterium tumefaciens T-DNA transport pore protein VirB8. J Bacteriol 183:3636–3641. [PubMed][CrossRef]
78. Terradot L, Bayliss R, Oomen C, Leonard GA, Baron C, Waksman G. 2005. Structures of two core subunits of the bacterial type IV secretion system, VirB8 from Brucella suis and ComB10 from Helicobacter pylori. Proc Natl Acad Sci USA 102:4596–4601. [PubMed][CrossRef]
79. Bailey S, Ward D, Middleton R, Grossmann JG, Zambryski PC. 2006. Agrobacterium tumefaciens VirB8 structure reveals potential protein-protein interaction sites. Proc Natl Acad Sci USA 103:2582–2587. [PubMed][CrossRef]
80. Porter CJ, Bantwal R, Bannam TL, Rosado CJ, Pearce MC, Adams V, Lyras D, Whisstock JC, Rood JI. 2012. The conjugation protein TcpC from Clostridium perfringens is structurally related to the type IV secretion system protein VirB8 from Gram-negative bacteria. Mol Microbiol 83:275–288. [PubMed][CrossRef]
81. Goessweiner-Mohr N, Grumet L, Arends K, Pavkov-Keller T, Gruber CC, Gruber K, Birner-Gruenberger R, Kropec-Huebner A, Huebner J, Grohmann E, Keller W. 2013. The 2.5 Å structure of the Enterococcus conjugation protein TraM resembles VirB8 type IV secretion proteins. J Biol Chem 288:2018–2028. [PubMed][CrossRef]
82. Kuroda T, Kubori T, Thanh Bui X, Hyakutake A, Uchida Y, Imada K, Nagai H. 2015. Molecular and structural analysis of Legionella DotI gives insights into an inner membrane complex essential for type IV secretion. Sci Rep 5:10912. doi:10.1038/srep10912. [CrossRef]
83. Paschos A, den Hartigh A, Smith MA, Atluri VL, Sivanesan D, Tsolis RM, Baron C. 2011. An in vivo high-throughput screening approach targeting the type IV secretion system component VirB8 identified inhibitors of Brucella abortus 2308 proliferation. Infect Immun 79:1033–1043. [PubMed][CrossRef]
84. Sarkar MK, Husnain SI, Jakubowski SJ, Christie PJ. 2013. Isolation of bacterial type IV machine subassemblies. Methods Mol Biol 966:187–204. [PubMed][CrossRef]
85. Jakubowski SJ, Kerr JE, Garza I, Krishnamoorthy V, Bayliss R, Waksman G, Christie PJ. 2009. Agrobacterium VirB10 domain requirements for type IV secretion and T pilus biogenesis. Mol Microbiol 71:779–794. [PubMed][CrossRef]
86. Fronzes R, Christie PJ, Waksman G. 2009. The structural biology of type IV secretion systems. Nat Rev Microbiol 7:703–714. [PubMed][CrossRef]
87. Winans SC, Burns DL, Christie PJ. 1996. Adaptation of a conjugal transfer system for the export of pathogenic macromolecules. Trends Microbiol 4:64–68. [PubMed][CrossRef]
88. de Jong MF, Sun YH, den Hartigh AB, van Dijl JM, Tsolis RM. 2008. Identification of VceA and VceC, two members of the VjbR regulon that are translocated into macrophages by the Brucella type IV secretion system. Mol Microbiol 70:1378–1396. [PubMed][CrossRef]
89. Myeni S, Child R, Ng TW, Kupko JJ III, Wehrly TD, Porcella SF, Knodler LA, Celli J. 2013. Brucella modulates secretory trafficking via multiple type IV secretion effector proteins. PLoS Pathog 9:e1003556. doi:10.1371/journal.ppat.1003556. [CrossRef]
90. Ke Y, Wang Y, Li W, Chen Z. 2015. Type IV secretion system of Brucella spp. and its effectors. Front Cell Infect Microbiol 5:72. doi:10.3389/fcimb.2015.00072. [PubMed][CrossRef]
91. Ou JT. 1975. Mating signal and DNA penetration deficiency in conjugation between male Escherichia coli and minicells. Proc Natl Acad Sci USA 72:3721–3725. [PubMed][CrossRef]
92. Lang S, Kirchberger PC, Gruber CJ, Redzej A, Raffl S, Zellnig G, Zangger K, Zechner EL. 2011. An activation domain of plasmid R1 TraI protein delineates stages of gene transfer initiation. Mol Microbiol 82:1071–1085. [PubMed][CrossRef]
93. Cascales E, Christie PJ. 2004. Agrobacterium VirB10, an ATP energy sensor required for type IV secretion. Proc Natl Acad Sci USA 101:17228–17233. [PubMed][CrossRef]
94. Banta LM, Kerr JE, Cascales E, Giuliano ME, Bailey ME, McKay C, Chandran V, Waksman G, Christie PJ. 2011. An Agrobacterium VirB10 mutation conferring a type IV secretion system gating defect. J Bacteriol 193:2566–2574. [PubMed][CrossRef]
95. Anthony KG, Klimke WA, Manchak J, Frost LS. 1999. Comparison of proteins involved in pilus synthesis and mating pair stabilization from the related plasmids F and R100-1: insights into the mechanism of conjugation. J Bacteriol 181:5149–5159. [PubMed]
96. Audette GF, Manchak J, Beatty P, Klimke WA, Frost LS. 2007. Entry exclusion in F-like plasmids requires intact TraG in the donor that recognizes its cognate TraS in the recipient. Microbiology 153:442–451. [PubMed][CrossRef]
97. Marrero J, Waldor MK. 2007. Determinants of entry exclusion within Eex and TraG are cytoplasmic. J Bacteriol 189:6469–6473. [PubMed][CrossRef]
98. Gillespie JJ, Ammerman NC, Dreher-Lesnick SM, Rahman MS, Worley MJ, Setubal JC, Sobral BS, Azad AF. 2009. An anomalous type IV secretion system in Rickettsia is evolutionarily conserved. PLoS One 4:e4833. doi:10.1371/journal.pone.0004833. [PubMed][CrossRef]
99. Gillespie JJ, Brayton KA, Williams KP, Diaz MA, Brown WC, Azad AF, Sobral BW. 2010. Phylogenomics reveals a diverse Rickettsiales type IV secretion system. Infect Immun 78:1809–1823. [PubMed][CrossRef]
100. Rancès E, Voronin D, Tran-Van V, Mavingui P. 2008. Genetic and functional characterization of the type IV secretion system in Wolbachia. J Bacteriol 190:5020–5030. [PubMed][CrossRef]
101. Nagai H, Roy CR. 2001. The DotA protein from Legionella pneumophila is secreted by a novel process that requires the Dot/Icm transporter. EMBO J 20:5962–5970. [PubMed][CrossRef]
102. Fischer W. 2011. Assembly and molecular mode of action of the Helicobacter pylori Cag type IV secretion apparatus. FEBS J 278:1203–1212. [PubMed][CrossRef]
103. Terradot L, Waksman G. 2011. Architecture of the Helicobacter pylori Cag-type IV secretion system. FEBS J 278:1213–1222. [PubMed][CrossRef]
104. Nakano N, Kubori T, Kinoshita M, Imada K, Nagai H. 2010. Crystal structure of Legionella DotD: insights into the relationship between type IVB and type II/III secretion systems. PLoS Pathog 6:e1001129. doi:10.1371/journal.ppat.1001129. [PubMed][CrossRef]
105. Souza DP, Andrade MO, Alvarez-Martinez CE, Arantes GM, Farah CS, Salinas RK. 2011. A component of the Xanthomonadaceae type IV secretion system combines a VirB7 motif with a N0 domain found in outer membrane transport proteins. PLoS Pathog 7:e1002031. doi:10.1371/journal.ppat.1002031. [CrossRef]
106. Ding H, Zeng H, Huang L, Dong Y, Duan Y, Mao X, Guo G, Zou Q. 2012. Helicobacter pylori chaperone-like protein CagT plays an essential role in the translocation of CagA into host cells. J Microbiol Biotechnol 22:1343–1349. [PubMed][CrossRef]
107. Johnson EM, Gaddy JA, Voss BJ, Hennig EE, Cover TL. 2014. Genes required for assembly of pili associated with the Helicobacter pylori cag type IV secretion system. Infect Immun 82:3457–3470. [PubMed][CrossRef]
108. Aras RA, Fischer W, Perez-Perez GI, Crosatti M, Ando T, Haas R, Blaser MJ. 2003. Plasticity of repetitive DNA sequences within a bacterial (Type IV) secretion system component. J Exp Med 198:1349–1360. [PubMed][CrossRef]
109. Rohde M, Püls J, Buhrdorf R, Fischer W, Haas R. 2003. A novel sheathed surface organelle of the Helicobacter pylori cag type IV secretion system. Mol Microbiol 49:219–234. [PubMed][CrossRef]
110. Barrozo RM, Cooke CL, Hansen LM, Lam AM, Gaddy JA, Johnson EM, Cariaga TA, Suarez G, Peek RM Jr, Cover TL, Solnick JV. 2013. Functional plasticity in the type IV secretion system of Helicobacter pylori. PLoS Pathog 9:e1003189. doi:10.1371/journal.ppat.1003189. [PubMed]
111. Segal G, Purcell M, Shuman HA. 1998. Host cell killing and bacterial conjugation require overlapping sets of genes within a 22-kb region of the Legionella pneumophila genome. Proc Natl Acad Sci USA 95:1669–1674. [PubMed][CrossRef]
112. Vogel JP, Andrews HL, Wong SK, Isberg RR. 1998. Conjugative transfer by the virulence system of Legionella pneumophila. Science 279:873–876. [PubMed][CrossRef]
113. Kelley LA, Sternberg MJ. 2009. Protein structure prediction on the Web: a case study using the Phyre server. Nat Protoc 4:363–371. [PubMed][CrossRef]
114. Henry T, Couillault C, Rockenfeller P, Boucrot E, Dumont A, Schroeder N, Hermant A, Knodler LA, Lecine P, Steele-Mortimer O, Borg JP, Gorvel JP, Méresse S. 2006. The Salmonella effector protein PipB2 is a linker for kinesin-1. Proc Natl Acad Sci USA 103:13497–13502. [PubMed][CrossRef]
115. Baisón-Olmo F, Cardenal-Muñoz E, Ramos-Morales F. 2012. PipB2 is a substrate of the Salmonella pathogenicity island 1-encoded type III secretion system. Biochem Biophys Res Commun 423:240–246. [PubMed][CrossRef]
116. Diao J, Zhang Y, Huibregtse JM, Zhou D, Chen J. 2008. Crystal structure of SopA, a Salmonella effector protein mimicking a eukaryotic ubiquitin ligase. Nat Struct Mol Biol 15:65–70. [PubMed][CrossRef]
117. Bernstein HD. 2010. Type V secretion: the autotransporter and two-partner secretion pathways. Ecosal Plus 4. doi:10.1128/ecosalplus.4.3.6. [PubMed]
118. Harrington LC, Rogerson AC. 1990. The F pilus of Escherichia coli appears to support stable DNA transfer in the absence of wall-to-wall contact between cells. J Bacteriol 172:7263–7264. [PubMed]
119. Babic A, Lindner AB, Vulic M, Stewart EJ, Radman M. 2008. Direct visualization of horizontal gene transfer. Science 319:1533–1536. [PubMed][CrossRef]
120. Lawley TD, Gordon GS, Wright A, Taylor DE. 2002. Bacterial conjugative transfer: visualization of successful mating pairs and plasmid establishment in live Escherichia coli. Mol Microbiol 44:947–956. [PubMed][CrossRef]
121. Jakubowski SJ, Cascales E, Krishnamoorthy V, Christie PJ. 2005. Agrobacterium tumefaciens VirB9, an outer-membrane-associated component of a type IV secretion system, regulates substrate selection and T-pilus biogenesis. J Bacteriol 187:3486–3495. [PubMed][CrossRef]
122. Bradley DE. 1980. Morphological and serological relationships of conjugative pili. Plasmid 4:155–169. [PubMed][CrossRef]
123. Bradley DE, Taylor DE, Cohen DR. 1980. Specification of surface mating systems among conjugative drug resistance plasmids in Escherichia coli K-12. J Bacteriol 143:1466–1470. [PubMed]
124. Paranchych W, Frost LS. 1988. The physiology and biochemistry of pili. Adv Microb Physiol 29:53–114. [PubMed][CrossRef]
125. Bayer M, Eferl R, Zellnig G, Teferle K, Dijkstra A, Koraimann G, Högenauer G. 1995. Gene 19 of plasmid R1 is required for both efficient conjugative DNA transfer and bacteriophage R17 infection. J Bacteriol 177:4279–4288. [PubMed]
126. Zupan J, Hackworth CA, Aguilar J, Ward D, Zambryski P. 2007. VirB1* promotes T-pilus formation in the vir-Type IV secretion system of Agrobacterium tumefaciens. J Bacteriol 189:6551–6563. [PubMed][CrossRef]
127. Majdalani N, Moore D, Maneewannakul S, Ippen-Ihler K. 1996. Role of the propilin leader peptide in the maturation of F pilin. J Bacteriol 178:3748–3754. [PubMed]
128. Majdalani N, Ippen-Ihler K. 1996. Membrane insertion of the F-pilin subunit is Sec independent but requires leader peptidase B and the proton motive force. J Bacteriol 178:3742–3747. [PubMed]
129. Maneewannakul K, Maneewannakul S, Ippen-Ihler K. 1993. Synthesis of F pilin. J Bacteriol 175:1384–1391. [PubMed]
130. Eisenbrandt R, Kalkum M, Lai EM, Lurz R, Kado CI, Lanka E. 1999. Conjugative pili of IncP plasmids, and the Ti plasmid T pilus are composed of cyclic subunits. J Biol Chem 274:22548–22555. [PubMed][CrossRef]
131. Eisenbrandt R, Kalkum M, Lurz R, Lanka E. 2000. Maturation of IncP pilin precursors resembles the catalytic Dyad-like mechanism of leader peptidases. J Bacteriol 182:6751–6761. [PubMed][CrossRef]
132. Paiva WD, Grossman T, Silverman PM. 1992. Characterization of F-pilin as an inner membrane component of Escherichia coli K12. J Biol Chem 267:26191–26197. [PubMed]
133. Paiva WD, Silverman PM. 1996. Effects of F-encoded components and F-pilin domains on the synthesis and membrane insertion of TraA-'PhoA fusion proteins. Mol Microbiol 19:1277–1286. [PubMed][CrossRef]
134. Kerr JE, Christie PJ. 2010. Evidence for VirB4-mediated dislocation of membrane-integrated VirB2 pilin during biogenesis of the Agrobacterium VirB/VirD4 type IV secretion system. J Bacteriol 192:4923–4934. [PubMed][CrossRef]
135. Frost LS. 2009. Conjugation, bacterial, p 294–308. In Schaechter M (ed), Desk Encyclopedia of Microbiology, 2nd ed, Academic Press, San Diego, CA. [CrossRef]
136. Wang YA, Yu X, Silverman PM, Harris RL, Egelman EH. 2009. The structure of F-pili. J Mol Biol 385:22–29. [PubMed][CrossRef]
137. Gilmour MW, Lawley TD, Rooker MM, Newnham PJ, Taylor DE. 2001. Cellular location and temperature-dependent assembly of IncHI1 plasmid R27-encoded TrhC-associated conjugative transfer protein complexes. Mol Microbiol 42:705–715. [PubMed][CrossRef]
138. Aly KA, Baron C. 2007. The VirB5 protein localizes to the T-pilus tips in Agrobacterium tumefaciens. Microbiology 153:3766–3775. [PubMed][CrossRef]
139. Harris RL, Silverman PM. 2004. Tra proteins characteristic of F-like type IV secretion systems constitute an interaction group by yeast two-hybrid analysis. J Bacteriol 186:5480–5485. [PubMed][CrossRef]
140. Arutyunov D, Arenson B, Manchak J, Frost LS. 2010. F plasmid TraF and TraH are components of an outer membrane complex involved in conjugation. J Bacteriol 192:1730–1734. [PubMed][CrossRef]
141. Harris RL, Hombs V, Silverman PM. 2001. Evidence that F-plasmid proteins TraV, TraK and TraB assemble into an envelope-spanning structure in Escherichia coli. Mol Microbiol 42:757–766. [PubMed][CrossRef]
142. Maneewannakul S, Maneewannakul K, Ippen-Ihler K. 1992. Characterization, localization, and sequence of F transfer region products: the pilus assembly gene product TraW and a new product, TrbI. J Bacteriol 174:5567–5574. [PubMed]
143. Dürrenberger MB, Villiger W, Bächi T. 1991. Conjugational junctions: morphology of specific contacts in conjugating Escherichia coli bacteria. J Struct Biol 107:146–156. [PubMed][CrossRef]
144. Achtman M, Kennedy N, Skurray R. 1977. Cell–cell interactions in conjugating Escherichia coli: role of traT protein in surface exclusion. Proc Natl Acad Sci USA 74:5104–5108. [PubMed][CrossRef]
145. Klimke WA, Rypien CD, Klinger B, Kennedy RA, Rodriguez-Maillard JM, Frost LS. 2005. The mating pair stabilization protein, TraN, of the F plasmid is an outer-membrane protein with two regions that are important for its function in conjugation. Microbiology 151:3527–3540. [PubMed][CrossRef]
146. Low B, Wood TH. 1965. A quick and efficient method for interruption of bacterial conjugation. Genet Res 6:300–303. [PubMed][CrossRef]
147. Anthony KG, Sherburne C, Sherburne R, Frost LS. 1994. The role of the pilus in recipient cell recognition during bacterial conjugation mediated by F-like plasmids. Mol Microbiol 13:939–953. [PubMed][CrossRef]
148. Firth N, Skurray R. 1992. Characterization of the F plasmid bifunctional conjugation gene, traG. Mol Gen Genet 232:145–153. [PubMed][CrossRef]
149. Samuels AL, Lanka E, Davies JE. 2000. Conjugative junctions in RP4-mediated mating of Escherichia coli. J Bacteriol 182:2709–2715. [PubMed][CrossRef]
150. Heinemann JA, Sprague GFJ Jr. 1989. Bacterial conjugative plasmids mobilize DNA transfer between bacteria and yeast. Nature 340:205–209. [PubMed][CrossRef]
151. Bates S, Cashmore AM, Wilkins BM. 1998. IncP plasmids are unusually effective in mediating conjugation of Escherichia coli and Saccharomyces cerevisiae: involvement of the tra2 mating system. J Bacteriol 180:6538–6543. [PubMed]
152. Waters VL. 2001. Conjugation between bacterial and mammalian cells. Nat Genet 29:375–376. [PubMed][CrossRef]
153. Silby MW, Ferguson GC, Billington C, Heinemann JA. 2007. Localization of the plasmid-encoded proteins TraI and MobA in eukaryotic cells. Plasmid 57:118–130. [PubMed][CrossRef]
154. Guynet C, Cuevas A, Moncalián G, de la Cruz F. 2011. The stb operon balances the requirements for vegetative stability and conjugative transfer of plasmid R388. PLoS Genet 7:e1002073. doi:10.1371/journal.pgen.1002073. [PubMed][CrossRef]
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/content/journal/ecosalplus/10.1128/ecosalplus.ESP-0020-2015
2016-08-04
2017-03-29

Abstract:

and other Gram-negative and -positive bacteria employ type IV secretion systems (T4SSs) to translocate DNA and protein substrates, generally by contact-dependent mechanisms, to other cells. The T4SSs functionally encompass two major subfamilies, the conjugation systems and the effector translocators. The conjugation systems are responsible for interbacterial transfer of antibiotic resistance genes, virulence determinants, and genes encoding other traits of potential benefit to the bacterial host. The effector translocators are used by many Gram-negative pathogens for delivery of potentially hundreds of virulence proteins termed effectors to eukaryotic cells during infection. In and other species of , T4SSs identified to date function exclusively in conjugative DNA transfer. In these species, the plasmid-encoded systems can be classified as the P, F, and I types. The P-type systems are the simplest in terms of subunit composition and architecture, and members of this subfamily share features in common with the paradigmatic VirB/VirD4 T4SS. This review will summarize our current knowledge of the systems and the P-type system, with emphasis on the structural diversity of the T4SSs. Ancestral P-, F-, and I-type systems were adapted throughout evolution to yield the extant effector translocators, and information about well-characterized effector translocators also is included to further illustrate the adaptive and mosaic nature of these highly versatile machines.

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Figures

Image of Figure 1
Figure 1

(P type) The VirB/VirD4 reference system with subunit enzymatic functions and associations with inner membrane complex (IMC), outer membrane complex (OMC), or pilus. PG Hydrolase, peptidoglycan hydrolase; T4CP, type IV coupling protein. (F type) Genes related to the genes are color coded. Genes encoding functions required for F pilus/retraction are shaded in dark gray, and for mating pair stabilization (Mps) or surface exclusion in light gray (VirB6-like TraG also functions in mating pair stabilization). Uppercase letters are genes, lowercase letters are genes. (I type) -like genes are color coded. Genes unique to the I-type systems encoding inner membrane proteins are in beige; genes encoding subunits that functionally interact with the DotL T4CP are in light-shaded purple. P- and I-type systems employ three ATPases related to VirD4, VirB4, and VirB11; F-type systems employ only homologs of VirD4 and VirB4. Unless otherwise indicated, the systems shown are functional in .

Citation: Christie P. 2016. The Mosaic Type IV Secretion Systems, EcoSal Plus 2016; doi:10.1128/ecosalplus.ESP-0020-2015
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Image of Figure 2
Figure 2

The R388 T4SS structure ( 26 ), presented schematically using the VirB/VirD4 reference nomenclature and as visualized by transmission electron microscopy. (A) The T4SS is composed of an extracellular pilus, an outer membrane complex (OMC), and inner membrane complex (IMC), the VirD4-like T4CP (substrate receptor) and, for most systems, a VirB11 ATPase. Substructures of the T4SS: The conjugative pilus was not part of the solved T4SS structure, but is postulated to associate with the structure as depicted. In the VirB/VirD4 T4SS, the pilus is composed of a fragment of the VirB1 transglycosylase (VirB1*), VirB2 pilin, and VirB5 tip protein ( 126 , 138 ). The OMC is composed of the VirB7, VirB9, and VirB10 subunits in copy numbers listed in parentheses ( 26 ). The VirB1 transglycosylase is required for pilus assembly but not for elaboration of the translocation channel. The IMC is composed of the VirB5, VirB8, VirB6, VirB3, and VirB4 subunits with copy numbers listed in parentheses ( 26 ). Other ATPases, including VirD4 and VirB11, were not part of the solved T4SS structure, but are postulated to associate with the IMC as depicted. Color-coding of the subunits matches that for the corresponding genes in Fig. 1 . (B) The subunits shown to form formaldehyde cross-links with the T-DNA substrate during transfer through the VirB/VirD4 T4SS with the TrIP assay. Red arrows denote the proposed translocation pathway ( 23 ). (C) The R388 structure solved by transmission electron microscopy, reproduced with permission by reference 26 . The OMC is postulated to house the translocation channel that extends through the periplasm and across the outer membrane. The OMC is connected to the IMC by a narrow stalk. Two hexamers of VirB4 extend into the cytoplasm and are postulated to establish contacts with the VirD4 T4CP and the VirB11 ATPase. (A and C) For both the schematic and solved T4SS structure, three possible routes of substrate translocation across the inner membrane are depicted in red dashed lines. A single route is postulated, in a red dashed line, through the OMC for substrate passage to the cell exterior (see text for details). IM, inner membrane; P, periplasm; OM, outer membrane.

Citation: Christie P. 2016. The Mosaic Type IV Secretion Systems, EcoSal Plus 2016; doi:10.1128/ecosalplus.ESP-0020-2015
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Figure 3

(A) The structural prototype of the T4CPs, R388-encoded TrwB, is a hexamer with a stem composed of the N-terminal transmembrane domains (NTDs) of the 6 protomers and a ball composed of the nucleotide binding domains (NBDs) and all-alpha-domains (AADs). (Left) A space-filling model of the TrwB hexamer showing the Connolly surface (red, negatively charged; blue, positively charged) and central channel connecting the cytoplasm to the periplasm. IM, inner membrane. (Right) A ribbon diagram of the NBD (multicolored) and AAD (green). In the assembled hexamer, the AAD sits at the entrance of the hexamer lumen. Images reproduced with permission by reference 43 . (B) Schematics display the domain architectures of P-types TrwB and VirD4 and F-type TraD; numbers represent domain junctions with residue numbers relative to the start codon. The AAD is boxed. Known or predicted properties are listed above each domain. TrwB lacks a C-terminal domain (CTD), but such domains are carried by other VirD4 homologs including F-type TraD. (C) The TraD T4CP in the inner membrane with the various domains listed. The extreme C terminus of the CTD (residues in parentheses) is negatively charged and forms specific contacts with C-terminal α-helical domains (purple cylinders) of the TraM Dtr accessory protein. TraM’s N-terminal ribbon-helix-helix domain (RHH; purple dots) mediates binding to sites located within the F plasmid sequence. The TraD-TraM interaction specifies F plasmid transfer through the F-encoded T4SS. IM, inner membrane.

Citation: Christie P. 2016. The Mosaic Type IV Secretion Systems, EcoSal Plus 2016; doi:10.1128/ecosalplus.ESP-0020-2015
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Figure 4

Polytopic VirB6 subunits with lengths of ∼300 residues are components of the IMC. Many T4SSs have larger forms of these subunits, designated extended-VirB6. These forms of VirB6 are composed of a polytopic VirB6-like domain and a hydrophilic domain as large as ∼1,000 residues. (Left) F-type F plasmids of encode large VirB6-like TraG subunits. These subunits participate in entry exclusion, which prevents nonproductive plasmid transfer between donor cells. TraG’s C-terminal domain extends or is delivered via the T4SS across the donor-donor cell junction, where it binds the entry exclusion protein TraS located in the inner membrane of the paired donor. This interaction might transduce a signal resulting in a conformational change in the T4SS that blocks nonproductive F plasmid transfer to other F-carrying cells ( 96 ). (Middle) Rickettsial P-type T4SSs are composed of 4 or more large VirB6 subunits whose hydrophilic domains are unrelated in sequence and which might be surface-displayed for target cell binding or immune evasion ( 98 , 99 , 100 ). (Right) The I-type Dot/Icm system of secretes the highly hydrophobic DotA (∼1,000 residues) to the milieu where it assembles as large ring-shaped complexes. DotA has a canonical signal sequence, which is thought to mediate DotA delivery through the General Secretory Pathway (GSP) across the inner membrane. In the periplasm, DotA is then recruited to the Dot/Icm T4SS for delivery across the outer membrane to the cell exterior ( 101 ).

Citation: Christie P. 2016. The Mosaic Type IV Secretion Systems, EcoSal Plus 2016; doi:10.1128/ecosalplus.ESP-0020-2015
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Figure 5

The outer membrane complexes (OMCs) of paradigmatic T4SSs are composed of the small (∼5-kDa) lipoprotein VirB7, outer membrane-associated VirB9, and envelope-spanning VirB10 (∼50-kDa). Many T4SSs have larger forms of the VirB7- and VirB10-like subunits that carry surface-displayed domains of functional importance. (Left) P-type T4SSs carry larger forms of VirB7-like CagT and VirB10-like CagY with repeat domains that are exposed on the cell surface. TM, transmembrane domain. (Middle) I-type T4SSs also carry larger forms of the VirB7- and VirB10-like proteins. VirB7-like DotD has an N0 domain that is thought to form an extra ring of structural importance for the OMC. DotG has an N-terminal transmembrane domain (TM), a C-terminal VirB10 structural fold ( 20 ), and internal structural folds similar to that of T3SS effector PipB2 and the effector SopA ( 114 , 116 ), as determined by Phyre2 structural modeling ( 113 ). It is proposed that these domains of DotG protrude through the OMC or are proteolytically released from the VirB10 scaffold domain for delivery into the eukaryotic cell where they exert effector activities. (Right) F-type T4SSs carry novel subcomplexes that may or may not be physically associated with the T4SS at the cell surface. The TraW/U/F/B/F/TrbI subunits mediate F pilus extension and retraction, TraN and VirB10-like TraG stabilize mating pairs and the TraT lipoprotein prevents redundant F plasmid transfer among donor cells through surface exclusion (see reference 22 ).

Citation: Christie P. 2016. The Mosaic Type IV Secretion Systems, EcoSal Plus 2016; doi:10.1128/ecosalplus.ESP-0020-2015
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