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Journal of Bacteriology, August 2004, p. 5480-5485, Vol. 186, No. 16
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.16.5480-5485.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Tra Proteins Characteristic of F-Like Type IV Secretion Systems Constitute an Interaction Group by Yeast Two-Hybrid Analysis

Robin L. Harris and Philip M. Silverman*

Program in Molecular, Cell and Developmental Biology, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104

Received 20 February 2004/ Accepted 13 May 2004

Using yeast two-hybrid screens, we have defined an interaction group of six Tra proteins encoded by the F plasmid and required by F+ cells to elaborate F pili. The six proteins are TraH, TraF, TraW, TraU, TrbI, and TrbB. Except for TrbI, these proteins were all identified as hallmarks of F-like type IV secretion systems (TFSSs), with no homologues among TFSS genes of P-type or I-type systems (T. Lawley, W. Klimke, M. Gubbins, and L. Frost, FEMS Microbiol. Lett. 224:1-15, 2003). Also with the exception of TrbI, which is an inner membrane protein, the remaining proteins are or are predicted to be periplasmic. TrbI consists of one membrane-spanning segment near its N terminus and an 88-residue, hydrophilic domain that extends into the periplasm. Hence, the proteins of this group probably form a periplasmic cluster in Escherichia coli. The interaction network identifies TraH as the most highly connected node, with two-hybrid links to TrbI, TraU, and TraF. As measured by transcriptional activation of lacZ, the TrbI-TraH interaction in Saccharomyces cerevisiae requires the TraH amino acid segment from residues 193 to 225. The TraU and TraF interactions are localized to C-terminal segments of TraH (amino acids 315 to 458 for TraF and amino acids 341 to 458 for TraU). The TrbI-TraH interaction with full-length (less the signal peptide) TraH is weak but increases 40-fold with N-terminal TraH deletions; the first 50 amino acids appear to be critical for inhibiting TrbI binding in yeast. Previous studies by others have shown that, with the exception of trbB mutations, which do not affect the elaboration or function of F pili under laboratory conditions, a mutation in any of the other genes in this interaction group alters the number or length distribution of F pili. We propose a model whereby one function of the TraH interaction group is to control F-pilus extension and retraction.

* Corresponding author. Mailing address: Program in Molecular, Cell and Developmental Biology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104. Phone: (405) 271-7663. Fax: (405) 271-3153. E-mail: silvermanp{at}omrf.ouhsc.edu.

Journal of Bacteriology, August 2004, p. 5480-5485, Vol. 186, No. 16
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.16.5480-5485.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Clarke, M., Maddera, L., Harris, R. L., Silverman, P. M. (2008). F-pili dynamics by live-cell imaging. Proc. Natl. Acad. Sci. USA 105: 17978-17981 [Abstract] [Full Text]  
  • Abajy, M. Y., Kopec, J., Schiwon, K., Burzynski, M., Doring, M., Bohn, C., Grohmann, E. (2007). A Type IV-Secretion-Like System Is Required for Conjugative DNA Transport of Broad-Host-Range Plasmid pIP501 in Gram-Positive Bacteria. J. Bacteriol. 189: 2487-2496 [Abstract] [Full Text]  
  • Audette, G. F., Manchak, J., Beatty, P., Klimke, W. A., Frost, L. S. (2007). Entry exclusion in F-like plasmids requires intact TraG in the donor that recognizes its cognate TraS in the recipient. Microbiology 153: 442-451 [Abstract] [Full Text]  
  • Elton, T. C., Holland, S. J., Frost, L. S., Hazes, B. (2005). F-Like Type IV Secretion Systems Encode Proteins with Thioredoxin Folds That Are Putative DsbC Homologues. J. Bacteriol. 187: 8267-8277 [Abstract] [Full Text]  
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  • Daehnel, K., Harris, R., Maddera, L., Silverman, P. (2005). Fluorescence assays for F-pili and their application. Microbiology 151: 3541-3548 [Abstract] [Full Text]  


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