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 (PubMed:9680224, PubMed:9786184). Pilot protein that is required for the proper localization of the secretin InvG/SctC in the outer membrane (PubMed:9680224, PubMed:9786184). Required for the secretion of the Sip virulence factors (PubMed:9680224, PubMed:23159244). Mutant shows decreased levels of InvG/SctC (PubMed:9786184). Deletion of the gene reduces the invasion efficiency of the bacterium to 70-80% as compared to wild-type in vitro (PubMed:23159244). SctG/invH-ssaV double mutant shows reduced secretion of Sip effector proteins (SipA, SipB, SipC and SipD) (PubMed:23159244). Belongs to the InvH family.