Function and distribution of EspG2, a type III secretion system effector of enteropathogenic Escherichia coli

The enteropathogenic Escherichia coli (EPEC) effector protein EspG, like the Shigella effector VirA, functions through disruption of the host cell microtubule network. Reports have differed as to whether the EspG homologue, EspG2, is also responsible for microtubule disruption. In this study we show that following translocation, EspG2 and VirA are localised under adherent bacteria and able to restore the microtubule disruption phenotype to an espG/espG2 double EPEC mutant. The espG/espG2 double mutant produced A/E lesions similar to wild-type EPEC on human intestinal in vitro organ cultures. Determining the distribution of espG and espG2 among clinical EPEC isolates revealed two different types of espG (espGα and espGβ) and espG2 (intact and pseudo genes), which were associated with specific EPEC serotypes and closely followed the EPEC lineage. This investigation has established a role for EspG2 in the disruption of the microtubule network and associated different espG and espG2 types with different groups of EPEC.