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Infection and Immunity, March 2002, p. 1193-1201, Vol. 70, No. 3
0019-9567/02/$04.00+0     DOI: 10.1128/IAI.70.3.1193-1201.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Membrane Localization of the S1 Subunit of Pertussis Toxin in Bordetella pertussis and Implications for Pertussis Toxin Secretion

Karen M. Farizo,{dagger}, Stefanie Fiddner, Anissa M. Cheung, and Drusilla L. Burns*

Laboratory of Respiratory and Special Pathogens, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892

Received 22 August 2001/ Returned for modification 16 October 2001/ Accepted 3 November 2001

Pertussis toxin is secreted from Bordetella pertussis with the assistance of the Ptl transport system, a member of the type IV family of macromolecular transporters. The S1 subunit and the B oligomer combine to form the holotoxin prior to export from the bacterial cell, although the site of assembly is not known. To better understand the pathway of pertussis toxin assembly and secretion, we examined the subcellular location of the S1 subunit, expressed with or without the B oligomer and the Ptl proteins. In wild-type B. pertussis, the majority of the S1 subunit that remained cell associated localized to the bacterial membranes. In mutants of B. pertussis that do not express pertussis toxin and/or the Ptl proteins, full-length S1, expressed from a plasmid, partitioned almost entirely to the bacterial membranes. Several lines of evidence strongly suggest that the S1 subunit localizes to the outer membrane of B. pertussis. First, we found that membrane-bound full-length S1 was almost completely insoluble in Triton X-100. Second, recombinant S1 previously has been shown to localize to the outer membrane of Escherichia coli (J. T. Barbieri, M. Pizza, G. Cortina, and R. Rappuoli, Infect. Immun. 58:999-1003, 1990). Third, the S1 subunit possesses a distinctive amino acid motif at its carboxy terminus, including a terminal phenylalanine, which is highly conserved among bacterial outer membrane proteins. By using site-directed mutagenesis, we determined that the terminal phenylalanine is critical for stable expression of the S1 subunit. Our findings provide evidence that prior to assembly with the B oligomer and independent of the Ptl proteins, the S1 subunit localizes to the outer membrane of B. pertussis. Thus, outer membrane-bound S1 may serve as a nucleation site for assembly with the B oligomer and for interactions with the Ptl transport system.

* Corresponding author. Mailing address: CBER, FDA, HFM-434, Building 29, Room 124, 8800 Rockville Pike, Bethesda, MD 20892. Phone: (301) 402-3553. Fax: (301) 402-2776. E-mail: burns{at}cber.fda.gov.

{dagger} Present address: Center for Biologics Evaluation and Research, Food and Drug Administration, Rockville, MD 20852.

Infection and Immunity, March 2002, p. 1193-1201, Vol. 70, No. 3
0019-9567/02/$04.00+0     DOI: 10.1128/IAI.70.3.1193-1201.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Burns, D. L., Fiddner, S., Cheung, A. M., Verma, A. (2004). Analysis of Subassemblies of Pertussis Toxin Subunits In Vivo and Their Interaction with the Ptl Transport Apparatus. Infect. Immun. 72: 5365-5372 [Abstract] [Full Text]  
  • Rambow-Larsen, A. A., Weiss, A. A. (2004). Temporal Expression of Pertussis Toxin and Ptl Secretion Proteins by Bordetella pertussis. J. Bacteriol. 186: 43-50 [Abstract] [Full Text]  
  • Stenson, T. H., Patton, A. K., Weiss, A. A. (2003). Reduced Glutathione Is Required for Pertussis Toxin Secretion by Bordetella pertussis. Infect. Immun. 71: 1316-1320 [Abstract] [Full Text]  


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