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. Forms homooligomers; most probably hexamers (By similarity). Interacts with GspL (By similarity). Membrane association is not an intrinsic property but requires the GspL gene product. Silenced by the DNA-binding protein H-NS under standard growth conditions. Part of a cryptic operon that encodes proteins involved in type II secretion machinery in other organisms, but is not expressed in strain K12. Belongs to the GSP E family.