Component of the type III secretion system (T3SS), also called injectisome, which is used to inject bacterial effector proteins into eukaryotic host cells (PubMed:9786184, PubMed:27974800, PubMed:30242280). Forms a ring-shaped multimeric structure with an apparent central pore in the outer membrane (PubMed:9786184, PubMed:21385715, PubMed:27974800, PubMed:30242280). 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:21385715, PubMed:23633951, PubMed:27974800, PubMed:30242280). Forms a stable homooligomeric complex (PubMed:9786184, PubMed:21385715, PubMed:23633951, PubMed:27974800, PubMed:30242280). The complex is composed of 15 subunits (PubMed:21385715, PubMed:23633951, PubMed:27974800). Localization to the outer membrane requires InvH/SctG. Insertion mutants are hypoinvasive in the HEp-2 cell assay. Belongs to the bacterial secretin family. T3SS SctC subfamily.