Recruitment of conjugative DNA transfer substrate to Agrobacterium type IV secretion apparatus

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 104; no. 50; pp. 20019 - 20024
• Main Authors: Guo, Minliang, Jin, Shouguang, Sun, Deying, Hew, Choy L, Pan, Shen Q
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 11-12-2007; National Acad Sciences
• Subjects: Agrobacterium tumefaciens; Agrobacterium tumefaciens - classification; Agrobacterium tumefaciens - genetics; Agrobacterium tumefaciens - metabolism; Amino Acid Sequence; Antibodies; Bacteria; bacterial diseases of plants; bacterial proteins; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; binding proteins; Binding sites; Biological Sciences; Biological Transport; Bryophyllum daigremontianum; conjugation; Conserved Sequence; Deoxyribonucleic acid; DNA; DNA, Bacterial - genetics; Eukaryotes; Eukaryotic cells; Genetic mutation; Membranes; Molecular Sequence Data; Mutation - genetics; Nucleoproteins; Plant cells; plant tumors; Plasmids; Plasmids - genetics; Protein Binding; protein-protein interactions; Proteins; Secretion; Sequence Alignment; Threonine - genetics; Threonine - metabolism; Transfection; transfer DNA; transporters; type IV secretion system; VirD2-binding protein
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0701738104

Bacterial type IV secretion system (T4SS) belongs to a growing class of evolutionarily conserved transporters that translocate DNA and proteins into a wide variety of organisms including bacterial and eukaryotic cells. Archetypal is the Agrobacterium tumefaciens VirB/D4 T4SS that transfers oncogenic T-DNA to various eukaryotic cells, which is transferred as a nucleoprotein T-complex with VirD2 as the pilot protein. As a derivative of plasmid conjugation systems, the VirB/D4 T4SS can also transfer certain mobilizable plasmids and bacterial proteins like VirE2 and VirF, although it is unknown how the membrane-bound T4SS recruits different transfer substrates. Here, we show that a cytoplasmic VirD2-binding protein (VBP) is involved in the recruitment of the T-complex to the energizing components of the T4SS, including VirD4, VirB4, and VirB11. VBP is also important for the recruitment of a conjugative plasmid to a different transfer system independent of VirB/D4. These data indicate that VBP functions as a previously unrecognized recruiting protein that helps couple nucleoprotein substrates to the appropriate transport sites for conjugative DNA transfers. VBP has three functionally redundant homologs, and similar homologs can be found in different bacterial genomes, suggesting a previously uncharacterized class of proteins involved in conjugative DNA transfers.