Component of the type III secretion system (T3SS), also called injectisome, which is used to inject bacterial effector proteins into eukaryotic host cells (PubMed:8437520). Forms a ring-shaped multimeric structure with an apparent central pore in the outer membrane (PubMed:11717255). Necessary for the secretion of Ipa invasins (PubMed:8437520). The core secretion machinery of the T3SS is composed of approximately 20 different proteins, including cytoplasmic components, a base, an export apparatus and a needle (PubMed:30107569). This subunit is part of the base, which anchors the injectisome in the bacterial cell envelope (PubMed:11717255). Forms a stable homooligomeric complex (PubMed:11717255). Interacts with the pilotin MxiM/SctG and the inner membrane ring outer protein MxiJ/SctJ (PubMed:11717255, PubMed:18940609). Localization to the outer membrane requires MxiM/SctG. Inactivated mutant strain is unable to invade HeLa cells and to provoke keratoconjunctivitis in guinea-pigs. Belongs to the bacterial secretin family. T3SS SctC subfamily.