Project: Research project

Project Details


DESCRIPTION (Adapted from the applicant's abstract): Campylobacter fetus is
a significant pathogen of cattle and immunocompromised humans. One of the
major virulence factors of C. fetus is its surface layer (S-layer), which
allows it to resist the bactericidal effects of normal and immune serum.
Despite significant advances in understanding the molecular mechanisms of
antigenic variation of surface layer proteins (SLPs, the subunits of the
S-layer), until recently little was known about the secretion and assembly
of SLPs. Preliminary data now reveal that C. fetus SLPs are transported by
a type I secretion system [Sap(C)DEF] similar to those that recognize
C-terminal secretion signals for the transport of toxins, proteases and
lipases from gram-negative bacteria. This relationship is demonstrated by
the inability of a C. fetus sapD mutant to produce or secrete SLPs,
suggesting a possible link between the secretion and synthesis of SLPs.
Furthermore, E. coli expressing C. fetus sapCDEF are able to specifically
secrete a C. fetus SLP (SapA), verifying the sufficiency of these genes for
SLP secretion. The ability of sapCDEF+ E. coli to secrete SLPs will be
exploited for the delineation of the SapA C-terminal secretion signal.

The investigators therefore propose the study of the mechanism of secretion
of C. fetus SLPs as a necessary component of the process by which a major
virulence factor of C. fetus is assembled, and as a model system for
examining the interactions between heterologous type I transporters. They
will do so in the following specific aims.

Specific Aim #1. To characterize the components of the SLP secretion
apparatus of C. fetus through the construction of additional mutations in
the secretion apparatus. Studies on the potential regulation of sapA
expression by intracellular SLPs will be performed to investigate a possible
link between SLP synthesis and secretion.

Specific Aim #2. To construct a C. fetus SLP secretion assay system using
the cloned sapCDEF genes in E. coli. They will use deletion and mutational
analyses to define the C. fetus SapA C-terminal secretion signal. The
ability of the SapA secretion to mediate the transport of normally
non-secreted proteins also will be assessed.
Effective start/end date8/1/984/30/04


  • National Institute of Allergy and Infectious Diseases: $108,919.00
  • National Institute of Allergy and Infectious Diseases: $105,021.00
  • National Institute of Allergy and Infectious Diseases: $101,962.00
  • National Institute of Allergy and Infectious Diseases


  • Medicine(all)
  • Immunology and Microbiology(all)


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