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 [1].

1: VirE2, a Type IV secretion substrate, interacts with the VirD4 transfer protein at cell poles of Agrobacterium tumefaciens. Atmakuri K, Ding Z, Christie PJ; Mol Microbiol 2003;49:1699-1713. PMID:12950931