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Infection and Immunity, June 2001, p. 4027-4033, Vol. 69, No. 6
Center for Vaccine Development and Department of
Microbiology and Immunology, University of Maryland School of Medicine,
Baltimore, Maryland 212011; Department
of Microbiology and Immunology, The University of Melbourne,
Parkville, Victoria 3052, Australia2;
Department of Biology, Reed College, Portland, Oregon
972023; and Division of Bacterial
Infection, Department of Microbiology and Immunology, Institute of
Medical Science, University of Tokyo, Minato-ku, Tokyo 108-8639, Japan4
Received 18 August 2000/Returned for modification 30 October
2000/Accepted 12 March 2001
The function of the rorf2 gene located on the locus
of enterocyte effacement (LEE) pathogenicity island of enteropathogenic Escherichia coli (EPEC) has not been described. We
report that rorf2 encodes a novel protein, named EspG,
which is secreted by the type III secretory system and which is
translocated into host epithelial cells. EspG is homologous with
Shigella flexneri protein VirA, and the cloned
espG (rorf2) gene can rescue invasion in a Shigella virA mutant, indicating that these proteins
are functionally equivalent in Shigella. An EPEC
espG mutant had no apparent defects in in vitro assays
of virulence phenotypes, but a rabbit diarrheagenic E.
coli strain carrying a mutant espG showed
diminished intestinal colonization and yet diarrheal attack rates
similar to those of the wild type. A second EspG homolog, Orf3,
is encoded on the EspC pathogenicity islet. The cloned
orf3 gene could also rescue invasion in a
Shigella virA mutant, but an EPEC espG
orf3 double mutant was not diminished in any tested in vitro
assays for EPEC virulence factors. Our results indicate that EspG plays
an accessory but as yet undefined role in EPEC virulence that may
involve intestinal colonization.
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.6.4027-4033.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
EspG, a Novel Type III System-Secreted Protein from
Enteropathogenic Escherichia coli with Similarities to
VirA of Shigella flexneri

*
Corresponding author. Mailing address: Center for
Vaccine Development, University of Maryland School of Medicine, 685 W. Baltimore St., Baltimore, MD 21201. Phone: (410) 706-2344. Fax: (410)
706-0182. E-mail: jkaper{at}umaryland.edu.
Present address: Department of Pediatric Infectious Diseases, Johns
Hopkins School of Medicine, Baltimore, MD 21205.
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