ATPase component of the type II secretion system required for the energy-dependent secretion of extracellular factors such as proteases and toxins from the periplasm. Acts as a molecular motor to provide the energy that is required for assembly of the pseudopilus and the extrusion of substrates generated in the cytoplasm. ATP + H2O + cellular proteinSide 1 = ADP + phosphate + cellular proteinSide 2. Homodimer (PubMed:9426126). Dimerization is directed by a relatively short domain near the extreme N-terminus and is essential for extracellular protein secretion (PubMed:9426126). May form homooligomers (PubMed:9426126). Interacts with XcpY/GspL (PubMed:9882649). Forms an inner membrane platform subcomplex with XcpS/GspF, XcpY/GspL and XcpZ/GspM (PubMed:16168578). Membrane association is not an intrinsic property but requires the XcpY/GspL gene product. By the two quorum-sensing circuits LasR-LasI and RhlR-RhlI in a growth-phase dependent manner. Mutants show complete loss of extracellular exotoxin A secretion. Belongs to the GSP E family.