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Infect Immun. 2016 Apr 22;84(5):1642-1649. doi: 10.1128/IAI.01562-15. Print 2016 May.

Binding of CFA/I Pili of Enterotoxigenic Escherichia coli to Asialo-GM1 Is Mediated by the Minor Pilin CfaE.

Author information

1
Menzies Health Institute Queensland, School of Medical Sciences, Griffith University, Southport, QLD, Australia.
2
Institute for Future Environments and School of Earth, Environmental and Biological Sciences, Queensland University of Technology, Brisbane, QLD, Australia.
3
Medicinal Chemistry and Drug Action, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, VIC, Australia.
4
Menzies Health Institute Queensland, School of Medical Sciences, Griffith University, Southport, QLD, Australia h.sakellaris@griffith.edu.au.
5
School of Pathology and Laboratory Medicine, University of Western Australia, Nedlands, WA, Australia.

Abstract

CFA/I pili are representatives of a large family of related pili that mediate the adherence of enterotoxigenic Escherichia coli to intestinal epithelial cells. They are assembled via the alternate chaperone-usher pathway and consist of two subunits, CfaB, which makes up the pilus shaft and a single pilus tip-associated subunit, CfaE. The current model of pilus-mediated adherence proposes that CFA/I has two distinct binding activities; the CfaE subunit is responsible for binding to receptors of unknown structure on erythrocyte and intestinal epithelial cell surfaces, while CfaB binds to various glycosphingolipids, including asialo-GM1. In this report, we present two independent lines of evidence that, contrary to the existing model, CfaB does not bind to asialo-GM1 independently of CfaE. Neither purified CfaB subunits nor CfaB assembled into pili bind to asialo-GM1. Instead, we demonstrate that binding activity toward asialo-GM1 resides in CfaE and this is essential for pilus binding to Caco-2 intestinal epithelial cells. We conclude that the binding activities of CFA/I pili for asialo-GM1, erythrocytes, and intestinal cells are inseparable, require the same amino acid residues in CfaE, and therefore depend on the same or very similar binding mechanisms.

PMID:
26975993
PMCID:
PMC4862694
DOI:
10.1128/IAI.01562-15
[Indexed for MEDLINE]
Free PMC Article

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