Component of the type IV secretion system VirB/VirD4 which could be a major virulence determinant for subversion of human endothelial cell (HEC) function. Altogether with virB11, may be implicated in providing the energy, via hydrolysis of ATP, for the assembly of secretion system and substrate transport. Interacts with virB10. Belongs to the TrbE/VirB4 family.