Component of the type VII secretion system (Ess). Required for the secretion of EsxA and proper accumulation of EssB and EssD. May oligomerize and interact with other membrane components to form the Ess system (PubMed:23006124). Interacts with EsaA (PubMed:29737367). Mutants cannot secrete EsxA. Deletion also affects the production of several Ess factors. Belongs to the EssB family.