@article{mbs:/content/journal/micro/10.1099/mic.0.2007/010462-0, author = "Aly, Khaled A. and Baron, Christian", title = "The VirB5 protein localizes to the T-pilus tips in Agrobacterium tumefaciens", journal= "Microbiology", year = "2007", volume = "153", number = "11", pages = "3766-3775", doi = "https://doi.org/10.1099/mic.0.2007/010462-0", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.2007/010462-0", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", keywords = "T4SS, type IV secretion system", keywords = "immuno-EM, immuno-electron microscopy", keywords = "EM, electron microscopy", keywords = "AS, acetosyringone", keywords = "T-DNA, transferred DNA", keywords = "TEM, transmission electron microscopy", abstract = "The Agrobacterium tumefaciens VirB/D4 type IV secretion system (T4SS) mediates the transfer of single-stranded DNA and protein virulence factors into plant cells, and also determines the assembly of the T-pilus, which is believed to play a role in host recognition. The T-pilus is composed of the major component VirB2 and the minor component VirB5. Using immuno-electron microscopy we detected the major component VirB2 along the entire length of detached T-pili, but not on cell-bound T-pili or on the cell surface. In contrast, the minor T-pilus component VirB5 was detected on the tips of cell-bound T-pili as well as on the ends of detached T-pili and on the cell surface. To gain further insights into the role of VirB5 we introduced changes at its C terminus. C-terminal deletions of up to four amino acids and alanine replacements did not abolish T-pilus formation and incorporation of the VirB5 variants at the tip, although they did impact the length of T-pili. Also, these changes differentially affected the ability of the T4SS to transfer DNA into plant and bacterial recipients, suggesting differential effects on host-cell specificity. The data presented here suggest that VirB5 localizes at the T-pilus tip, and provide novel insights into its role during the type IV secretion process.", }