The Export of Coat Protein from Enteroaggregative Escherichia coli by a Specific ATP-binding Cassette Transporter System*
- Junichiro Nishi‡§,
- Jalaluddin Sheikh‡,
- Kenji Mizuguchi¶∥,
- Ben Luisi¶∥,
- Valerie Burland**,
- Adam Boutin**,
- Debra J. Rose**,
- Frederick R. Blattner** and
- James P. Nataro‡‡‡§§
- Center for Vaccine Development, ‡Departments of Pediatrics, ‡‡Medicine, and §§Microbiology & Immunology, University of Maryland School of Medicine, Baltimore, Maryland 21201, the ¶Department of Biochemistry, University of Cambridge, 80 Tennis Court Rd., Cambridge CB2 1GA, United Kingdom, and the **Laboratory for Molecular and Computational Genomics, University of Wisconsin-Madison, Madison, Wisconsin 53706
- § To whom correspondence should be addressed (present address): Dept. of Pediatrics, Graduate School of Medical and Dental Sciences, Kagoshima University, Sakuragaoka 8-35-1, Kagoshima 890-8520, Japan. Tel.: 81-99-275-5354; Fax: 81-99-265-7196; E-mail: nishi1{at}m2.kufm.kagoshima-u.ac.jp.
Abstract
Enteroaggregative Escherichia coli (EAEC) is an emerging enteric pathogen characterized by aggregative adherence (AA) to cultured human mucosal epithelium cells. We have recently characterized a 10.2-kDa protein, called dispersin, which is exported from the bacteria and which promotes dispersal of EAEC across the intestinal mucosa. Here, we present evidence that dispersin is exported by a putative ABC transporter complex, which is encoded by a genetic locus of the EAEC virulence plasmid pAA2. We demonstrate that the locus comprises a cluster of five genes (designated aat-PABCD), including homologs of an inner-membrane permease (AatP), an ATP-binding cassette protein (AatC) and the outer membrane protein TolC (AatA). We show that, like TolC, AatA localizes to the outer membrane independently of its ABC partner. Dispersin appears to require the Aat complex for outer membrane translocation but not for secretion across the inner membrane. We also show that, like the dispersin gene, transcription of the aat cluster is dependent on AggR, a regulator of virulence genes in EAEC. We propose that the aat cluster encodes a specialized ABC transporter, which plays a role in the pathogenesis of EAEC by transporting dispersin out of the bacterial cell.
Footnotes
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↵1 The abbreviations used are: EAEC, enteroaggregative E. coli; AA, aggregative adherence; AAF, aggregative adherence fimbriae; DMEM, Dulbecco's modified Eagle's medium; RT, reverse transcriptase; PBS, phosphate-buffered saline; ORF, open reading frame.
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↵2 M. Cohen and J. Nataro, unpublished data.
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↵3 R. Marques and J. Nataro, unpublished data.
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↵4 E. Dudley and J. Nataro, unpublished data.
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The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EBI Data Bank with accession number(s) AY351860.
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↵* This work was supported in part by United States Public Health Services Grants AI33096 (to J. P. N.) and AI44387 (to F. R. B.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵∥ Supported by the Wellcome Trust.
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- Received June 17, 2003.
- Revision received August 19, 2003.
- The American Society for Biochemistry and Molecular Biology, Inc.
