EspG, a novel type III system-secreted protein from enteropathogenic Escherichia coli with similarities to virA of Shigella flexneri

Abstract

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 diarrhea-genic E. coli strain carrying a mutant espG sho..