Abstract
Bacterial Type IV Secretion Systems (T4SSs) are nanomachines that transport effector proteins or protein-DNA complexes to the extracellular milieu or to a target cell. The Xanthomonas citri T4SS (XAC-T4SS) belongs to the class of minimized T4SSs. Minimized T4SSs consist of eleven VirB subunits (VirB1 to VirB11) and the coupling protein VirD4. Expanded T4SSs have acquired additional subuni…