Many bacterial pathogens deliver effector proteins into host cells via a type III secretion system. These effector proteins then alter the host cell's biology in ways that are advantageous to the pathogen. The NleG protein and its homologues form the largest family of effector proteins in the enterohemorrhagic Escherichia coli O157:H7, with 14 members identified in the Sakai strain alone [1].

1: An extensive repertoire of type III secretion effectors in Escherichia coli O157 and the role of lambdoid phages in their dissemination. Tobe T, Beatson SA, Taniguchi H, Abe H, Bailey CM, Fivian A, Younis R, Matthews S, Marches O, Frankel G, Hayashi T, Pallen MJ; Proc Natl Acad Sci U S A. 2006;103:14941-14946. PMID:16990433