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Journal of Bacteriology, November 2008, p. 6961-6969, Vol. 190, No. 21
0021-9193/08/$08.00+0     doi:10.1128/JB.00996-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

PilF Is an Outer Membrane Lipoprotein Required for Multimerization and Localization of the Pseudomonas aeruginosa Type IV Pilus Secretin{triangledown}

Jason Koo,1,2 Stephanie Tammam,1,2 Shao-Yang Ku,1,2 Liliana M. Sampaleanu,2 Lori L. Burrows,2,3* and P. Lynne Howell1,2*

Department of Biochemistry, University of Toronto, Ontario, Canada,1 Program in Molecular Structure and Function, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada,2 Michael G. DeGroote Institute for Infectious Diseases Research and Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada3

Received 18 July 2008/ Accepted 25 August 2008

Type IV pili (T4P) are retractile appendages that contribute to the virulence of bacterial pathogens. PilF is a Pseudomonas aeruginosa lipoprotein that is essential for T4P biogenesis. Phenotypic characterization of a pilF mutant confirmed that T4P-mediated functions are abrogated: T4P were no longer present on the cell surface, twitching motility was abolished, and the mutant was resistant to infection by T4P retraction-dependent bacteriophage. The results of cellular fractionation studies indicated that PilF is the outer membrane pilotin required for the localization and multimerization of the secretin, PilQ. Mutation of the putative PilF lipidation site untethered the protein from the outer membrane, causing secretin assembly in both inner and outer membranes. T4P-mediated twitching motility and bacteriophage susceptibility were moderately decreased in the lipidation site mutant, while cell surface piliation was substantially reduced. The tethering of PilF to the outer membrane promotes the correct localization of PilQ and appears to be required for the formation of stable T4P. Our 2.0-Å structure of PilF revealed a superhelical arrangement of six tetratricopeptide protein-protein interaction motifs that may mediate the contacts with PilQ during secretin assembly. An alignment of pseudomonad PilF sequences revealed three highly conserved surfaces that may be involved in PilF function.

* Corresponding author. Mailing address for P. L. Howell: Program in Molecular Structure and Function, The Hospital for Sick Children, 555 University Avenue, Toronto M5G 1X8, ON, Canada. Phone: (416) 813-5378. Fax: (416) 813-5379. E-mail: howell{at}sickkids.ca. Mailing address for L. L. Burrows: Biochemistry and Biomedical Sciences, 4H18 Health Sciences Centre, McMaster University, 1200 Main Street West, Hamilton, ON L8N 3Z5, Canada. Phone: (905) 525-9140, ext. 22029. Fax: (905) 522-9033. E-mail: burrowsl{at}mcmaster.ca

{triangledown} Published ahead of print on 5 September 2008.

Journal of Bacteriology, November 2008, p. 6961-6969, Vol. 190, No. 21
0021-9193/08/$08.00+0     doi:10.1128/JB.00996-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Harvey, H., Habash, M., Aidoo, F., Burrows, L. L. (2009). Single-Residue Changes in the C-Terminal Disulfide-Bonded Loop of the Pseudomonas aeruginosa Type IV Pilin Influence Pilus Assembly and Twitching Motility. J. Bacteriol. 191: 6513-6524 [Abstract] [Full Text]  
  • Seo, J., Brencic, A., Darwin, A. J. (2009). Analysis of Secretin-Induced Stress in Pseudomonas aeruginosa Suggests Prevention Rather than Response and Identifies a Novel Protein Involved in Secretin Function. J. Bacteriol. 191: 898-908 [Abstract] [Full Text]  


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