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J. Bacteriol., 11 1996, 6546-6554, Vol 178, No. 22
M Stein, B Kenny, MA Stein and BB Finlay
Enteropathogenic Escherichia coli (EPEC) secretes at least five proteins.
Two of these proteins, EspA and EspB (previously called EaeB), activate
signal transduction pathways in host epithelial cells. While the role of
the other three proteins (39, 40, and 110 kDa) remains undetermined,
secretion of all five proteins is under the control of perA, a known
positive regulator of several EPEC virulence factors. On the basis of
amino-terminal protein sequence data, we cloned and sequenced the gene
which encodes the 110-kDa secreted protein and examined its possible role
in EPEC signaling and interaction with epithelial cells. In accordance with
the terminology used for espA and espB, we called this gene espC, for
EPEC-secreted protein C. We found significant homology between the
predicted EspC protein sequence and a family of immunoglobulin A (IgA)
protease-like proteins which are widespread among pathogenic bacteria.
Members of this protein family are found in avian pathogenic Escherichia
coli (Tsh), Haemophilus influenzae (Hap), and Shigella flexneri (SepA).
Although these proteins and EspC do not encode IgA protease activity, they
have considerable homology with IgA protease from Neisseria gonorrhoeae and
H. influenzae and appear to use a export system for secretion. We found
that genes homologous to espC also exist in other pathogenic bacteria which
cause attaching and effacing lesions, including Hafnia alvei biotype 19982,
Citrobacter freundii biotype 4280, and rabbit diarrheagenic E. coli
(RDEC-1). Although these strains secrete various proteins similar in
molecular size to the proteins secreted by EPEC, we did not detect
secretion of a 110-kDa protein by these strains. To examine the possible
role of EspC in EPEC interactions with epithelial cells, we constructed a
deletion mutant in espC by allelic exchange and characterized the mutant by
standard tissue culture assays. We found that EspC is not necessary for
mediating EPEC-induced signal transduction in HeLa epithelial cells and
does not play a role in adherence or invasion of tissue culture cells.
Copyright © 1996, American Society for Microbiology
Characterization of EspC, a 110-kilodalton protein secreted by enteropathogenic Escherichia coli which is homologous to members of the immunoglobulin A protease-like family of secreted proteins
Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, Canada.
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