ssT-DNA-protein complex is transferred to the plant nucleus, and during the translocation it passes through three membranes, the plant cell wall and cellular spaces. The ssT-DNA-VirD2 complex formed after the cleavage is coated by the 69 kDa VirE2 protein. The VirE2 protein is a single strand DNA binding protein. It prevents the DNA from the attack of nucleases, and also helps in making the translocation through the membrane channels easier. However, this association does not stabilize T-DNA complex inside Agrobacterium (Zupan et al., 1996). VirE2 and VirD2 both contain plant nuclear location signals (NLS): VirE2 contains two and VirD2 contains one. The presence of NLS indicates that these proteins play pivotal role after the ssT-DNA-protein complex is inside the plant cell and mediate its uptake to the nucleus.
However, an alternative model of T-DNA transfer “proposes that the transfer complex is a single-strand DNA covalently bound at its 5′-end with VirD2, but uncoated by VirE2” (de la Riva et al., 1998). It is proposed that VirE2 is exported independently to the plant cell, and once the naked ssT-DNA-VirD2 complex is inside the plant cell, it is coated by VirE2.