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Journal of Bacteriology, September 2004, p. 6186-6197, Vol. 186, No. 18
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.18.6186-6197.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

New Protein-Protein Interactions Identified for the Regulatory and Structural Components and Substrates of the Type III Secretion System of the Phytopathogen Xanthomonas axonopodis Pathovar citri

Marcos C. Alegria,¹ Cassia Docena,¹ Leticia Khater,^2,3 Carlos H. I. Ramos,^2,3 Ana C. R. da Silva,¹ and Chuck S. Farah^1*

Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo,¹ Centro de Biologia Molecular Estrutural, Laboratório Nacional de Luz Síncrotron,² Departamento de Bioquímica, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, Brazil³

Received 12 March 2004/ Accepted 11 June 2004

We have initiated a project to identify protein-protein interactions involved in the pathogenicity of the bacterial plant pathogen Xanthomonas axonopodis pv. citri. Using a yeast two-hybrid system based on Gal4 DNA-binding and activation domains, we have focused on identifying interactions involving subunits, regulators, and substrates of the type III secretion system coded by the hrp (for hypersensitive response and pathogenicity), hrc (for hrp conserved), and hpa (for hrp associated) genes. We have identified several previously uncharacterized interactions involving (i) HrpG, a two-component system response regulator responsible for the expression of X. axonopodis pv. citri hrp operons, and XAC0095, a previously uncharacterized protein encountered only in Xanthomonas spp.; (ii) HpaA, a protein secreted by the type III secretion system, HpaB, and the C-terminal domain of HrcV; (iii) HrpB1, HrpD6, and HrpW; and (iv) HrpB2 and HrcU. Homotropic interactions were also identified for the ATPase HrcN. These newly identified protein-protein interactions increase our understanding of the functional integration of phytopathogen-specific type III secretion system components and suggest new hypotheses regarding the molecular mechanisms underlying Xanthomonas pathogenicity.

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* Corresponding author. Mailing address: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes, 748, CEP 05599-970 São Paulo-SP, Brazil. Phone: 55-11-3091-3312. Fax: 55-11-3815-5579. E-mail: chsfarah{at}iq.usp.br.

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Journal of Bacteriology, September 2004, p. 6186-6197, Vol. 186, No. 18
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.18.6186-6197.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Lorenz, C., Buttner, D. (2009). Functional Characterization of the Type III Secretion ATPase HrcN from the Plant Pathogen Xanthomonas campestris pv. vesicatoria. J. Bacteriol. 191: 1414-1428 [Abstract] [Full Text]  
• Alegria, M. C., Souza, D. P., Andrade, M. O., Docena, C., Khater, L., Ramos, C. H. I., da Silva, A. C. R., Farah, C. S. (2005). Identification of New Protein-Protein Interactions Involving the Products of the Chromosome- and Plasmid-Encoded Type IV Secretion Loci of the Phytopathogen Xanthomonas axonopodis pv. citri. J. Bacteriol. 187: 2315-2325 [Abstract] [Full Text]