Involved in the synthesis of the type III secretion system (T3SS), also called injectisome, which is used to inject bacterial effector proteins into eukaryotic host cells (By similarity). Pilot protein that is required for the proper localization of the secretin InvG/SctC in the outer membrane (By similarity). Necessary for efficient adherence and entry of these organisms into cultured epithelial cells (PubMed:8382333). Belongs to the InvH family.