This family consists of several VirE2 proteins which seem to be specific to Agrobacterium tumefaciens and Rhizobium etli. VirE2 is known to interact, via its C-terminus, with VirD4. Agrobacterium tumefaciens transfers oncogenic DNA and effector proteins to plant cells during the course of infection. Substrate translocation across the bacterial cell envelope is mediated by a type IV secretion (TFS) system composed of the VirB proteins, as well as VirD4, a member of a large family of inner membrane proteins implicated in the coupling of DNA transfer intermediates to the secretion machine. VirE2 is therefore thought to be a protein substrate of a type IV secretion system which is recruited to a member of the coupling protein superfamily.