Required for secretion of the LtxA leukotoxin and resistance to various antimicrobial compounds. Homotrimer (PubMed:18633280). Probably part of a complex composed of LtxB, LtxD and TdeA, which forms a single transport channel across the two membranes (PubMed:17116373). The periplasmic domain interacts in vitro with purified peptidoglycans. Mutant cannot secrete leukotoxin and is more sensitive to clotrimazole, erythromycin, ethidium bromide, cationic detergents, bile-acids, anionic detergents and chloramphenicol. Belongs to the outer membrane factor (OMF) (TC 1.B.17) family.