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Infection and Immunity, November 2001, p. 6573-6579, Vol. 69, No. 11
Department of Chemistry, Biology and Chemical Engineering,
Ryerson University,1 and Division of
Infection, Immunity, Injury and Repair, Research Institute,
Hospital for Sick Children,3 Toronto, Ontario,
Canada, and Centro de Investigaciones en Ciencas
Microbiologicas, Benemerita Universidad Autonoma de Puebla, Puebla,
Mexico2
Received 19 January 2001/Returned for modification 25 May
2001/Accepted 31 July 2001
The bundle-forming pilus (BFP) of enteropathogenic
Escherichia coli (EPEC), an established
virulence factor encoded on the EPEC adherence factor (EAF) plasmid,
has been implicated in the formation of bacterial autoaggregates and in
the localized adherence of EPEC to cultured epithelial cells. While
understanding of the pathogenic mechanism of this organism is rapidly
improving, a receptor ligand for BFP has not yet been identified. We
now report, using both solid-phase and liposome binding assays, that
BFP expression correlates with phosphatidylethanolamine (PE) binding.
In a thin-layer chromatogram overlay assay, specific recognition of PE
was documented for BFP-expressing strains, including E2348/69, a
wild-type EPEC clinical isolate, as well as a laboratory strain, HB101,
transformed with a bfp-carrying plasmid. Strains which
did not express BFP did not bind PE, including a bfpA
disruptional mutant of E2348/69, EAF plasmid-cured E2348/69, and HB101.
E2348/69 also aggregated PE-containing liposomes but not
phosphatidylcholine- or phosphatidylserine-containing liposomes, while
BFP-negative strains did not produce aggregates with any
tested liposomes. Purified BFP preparations bound commercial PE
standards as well as a PE-containing band within lipid extracts from
human epithelial cells and from E2348/69. Our results therefore indicate a specific interaction between BFP and PE and suggest that PE
may serve as a BFP receptor for bacterial autoaggregation and may
promote localized adherence to host cells, both of which contribute to
bacterial pathogenesis.
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.11.6573-6579.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Enteropathogenic Escherichia coli
Virulence Factor Bundle-Forming Pilus Has a Binding Specificity
for Phosphatidylethanolamine
*
Corresponding author. Mailing address: Department of
Chemistry, Biology and Chemical Engineering, Ryerson University,
Toronto, Ontario, Canada M5B 2K3. Phone: (416) 979 5000, ext. 6345. Fax: (416) 979 5044. E-mail: dfoster{at}acs.ryerson.ca.
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