The type IV secretion system VirB/VirD4 is a major virulence determinant for subversion of human endothelial cell (HEC) function. VirB-dependent changes of HEC include massive cytoskeletal rearrangements, a pro-inflammatory activation by nuclear factor NF-kappa-B, inhibition of early and late events of apoptosis, leading to an increased cell survival, and, at high infection doses, a cytostatic or cytotoxic effect, which interfers with a potent VirB-independent mitogenic activity. These changes of HEC require the T4S coupling protein VirD4 and at least one of the effector proteins BepA-G. VirB3 may play a role in stabilization of pilus structure. Interacts with the 17 kDa antigen protein that is encoded within the virB locus. During the interaction with the intracellular environment of host cells. Belongs to the virB3 family.