Ordered translocation of 987P fimbrial subunits through the outer membrane of Escherichia coli

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Monitoring the Assembly of a Secreted Bacterial Virulence Factor Using Site-specific Crosslinking

Published on: December 17, 2013

J Cao1, A S Khan, M E Bayer

  • 1Department of Pathobiology, University of Pennsylvania School of Veterinary Medicine, Philadelphia 19104, USA.

Journal of Bacteriology
|July 1, 1995
PubMed

Insights

Enterotoxigenic Escherichia coli uses the 987P fimbria, composed of FasA, FasG, and a newly identified FasF minor subunit, for piglet intestinal cell adhesion. FasG acts as the tip adhesin, FasF as a linker, and FasA forms the shaft.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Bacterial Pathogenesis

Background:

  • Enterotoxigenic Escherichia coli (ETEC) utilizes fimbriae for host colonization.
  • The 987P fimbria is a key virulence factor in ETEC infections, particularly in piglets.
  • The 987P fimbria is a heteropolymer composed of major and minor subunits, with FasG identified as the adhesin.

Purpose of the Study:

  • To identify and characterize novel minor components of the 987P fimbria.
  • To elucidate the roles of minor subunits in fimbrial structure and function.
  • To determine the order of subunit export during 987P fimbria biogenesis.

Main Methods:

  • Development of anti-FasF antibody probes for protein identification.
  • Purification of 987P fimbriae.
  • Immune electron microscopy for protein localization.
  • Enzyme-linked immunosorbent assay (ELISA) inhibition assays.
  • Analysis of nonfimbriated mutants (fasG, fasF, fasA).

Main Results:

  • Identification of FasF as a novel minor fimbrial component with sequence similarity to FasA.
  • Localization of FasG and FasF at the fimbrial tip and along the fimbrial length.
  • Demonstration of a specific export order: FasG first, FasF second, and FasA third.
  • Evidence that subunit translocation precedes heteropolymerization.

Conclusions:

  • The 987P fimbria is a heteropolymer comprising FasA, FasG (tip adhesin), and FasF (linker molecule).
  • FasF is a newly identified minor component crucial for fimbrial assembly.
  • Subunit export order is critical for proper fimbrial biogenesis, with translocation preceding polymerization.

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