ATPase component of the type IV pilus (T4P) that plays a role in surface and host cell adhesion, colonization, biofilm maturation, virulence, and twitching, a form of surface-associated motility facilitated by cycles of extension, adhesion, and retraction of T4P fibers (PubMed:7854122, PubMed:10377148, PubMed:15659660, PubMed:18174131). Functions as a PilT-dependent retraction ATPase, providing a functional coupling between PilT and PilU and an optimal mechanism for pilus retraction (PubMed:31525185, PubMed:31626631). Homohexamer (PubMed:31626631). Interacts with PilT (Probable). Localizes only to the piliated pole. The N-terminal region is responsible for proper localization to the piliated pole. Mutants are hyperfimbriate, retain surface pili but have lost twitching motility (PubMed:7854122). In a mouse model of acute pneumonia, a decreased colonization of the liver is observed but not of the lung relative to the parental strain (PubMed:10377148). Belongs to the GSP E family.