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Journal of Bacteriology, May 2009, p. 2985-2992, Vol. 191, No. 9
0021-9193/09/$08.00+0     doi:10.1128/JB.01426-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Interactions between Brucella suis VirB8 and Its Homolog TraJ from the Plasmid pSB102 Underline the Dynamic Nature of Type IV Secretion Systems{triangledown} ,{dagger}

Gisèle Bourg, Romain Sube, David O'Callaghan, and Gilles Patey*

INSERM ESPRI 26, Université Montpellier 1 ERA 4204, Faculté de Médecine, Avenue Kennedy, CS 83021, 30908 Nîmes Cédex 2, France

Received 10 October 2008/ Accepted 6 February 2009

The proteinVirB8 plays a critical role in the assembly and function of the Agrobacterium tumefaciens virB type IV secretion system (T4SS). The structure of the periplasmic domain of both A. tumefaciens and Brucella suis VirB8 has been determined, and site-directed mutagenesis has revealed amino acids involved in the dimerization of VirB8 and interactions with VirB4 and VirB10. We have shown previously that TraJ, the VirB8 homologue from pSB102, and the chimeric protein TraJB8, encompassing the cytoplasmic and transmembrane (TM) domains of TraJ and the periplasmic domain of VirB8, were unable to complement a B. suis mutant containing an in-frame deletion of the virB8 gene. This suggested that the presence of the TraJ cytoplasmic and TM domains could block VirB8 dimerization or assembly in the inner membrane. By bacterial two-hybrid analysis, we found that VirB8, TraJ, and the chimeras can all interact to form both homo- and heterodimers. However, the presence of the TM domain of TraJ resulted in much stronger interactions in both the homo- and heterodimers. We expressed the wild-type and chimeric proteins in wild-type B. suis. The presence of proteins carrying the TM domain of TraJ had a dominant negative effect, leading to complete loss of virulence. This suggests that the T4SS is a dynamic structure and that strong interactions block the spatial flexibility required for correct assembly and function.

* Corresponding author. Mailing address: INSERM ESPRI 26, Université Montpellier 1 ERA 4204, Faculté de Médecine, Avenue Kennedy, CS 83021, 30908 Nîmes Cédex 2, France. Phone: 33 4 66 02 81 49. Fax: 33 4 66 02 81 48. E-mail: gilles.patey{at}univ-montpl.fr

{triangledown} Published ahead of print on 27 February 2009.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, May 2009, p. 2985-2992, Vol. 191, No. 9
0021-9193/09/$08.00+0     doi:10.1128/JB.01426-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Alvarez-Martinez, C. E., Christie, P. J. (2009). Biological Diversity of Prokaryotic Type IV Secretion Systems. Microbiol. Mol. Biol. Rev. 73: 775-808 [Abstract] [Full Text]  


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