Identification of New Protein-Protein Interactions Involving the Products of the Chromosome- and Plasmid-Encoded Type IV Secretion Loci of the PhytopathogenXanthomonas axonopodispv. citri

• DOI: 10.1128/jb.187.7.2315-2325.2005
• Publication Date: 2005-03-17T21:41:33Z
• Authors: Marcos C. Alegria; Diorge P. Souza; Maxuel O. Andrade; Cassia Docena; Leticia Khater; Carlos H. I. Ramos; Ana C. R. da Silva; Chuck S. Farah
• Keywords: 0303 health sciences; Xanthomonas; Base Sequence; Molecular Sequence Data; Chromosome Mapping; Chromosomes, Bacterial; 03 medical and health sciences; Bacterial Proteins; Genes, Bacterial; Two-Hybrid System Techniques; Amino Acid Sequence; Sequence Alignment; Plasmids; Protein Binding

ABSTRACTThe recently sequenced genome of the bacterial plant pathogenXanthomonas axonopodispv. citri contains twovirBgene clusters, one on the chromosome and one on a 64-kb plasmid, each of which codes for a previously uncharacterized type IV secretion system (T4SS). Here we used a yeast two-hybrid assay to identify protein-protein interactions in these two systems. Our results revealed interactions between known T4SS components as well as previously uncharacterized interactions involving hypothetical proteins coded by open reading frames in the twoX. axonopodispv. citrivirBloci. Our results indicate that both loci may code for previously unidentified VirB7 proteins, which we show interact with either VirB6 or VirB9 or with a hypothetical protein coded by the same locus. Furthermore, a set of previously uncharacterizedXanthomonasproteins have been found to interact with VirD4, whose gene is adjacent to the chromosomalvirBlocus. The gene for one member of this family is found within the chromosomalvirBlocus. All these uncharacterized proteins possess a conserved 120-amino-acid domain in their C termini and may represent a family of cofactors or substrates of theXanthomonasT4SS.