Component of the type VII secretion system (Ess). Required for the secretion of substrates including EsxA and EsxB (PubMed:27130157, PubMed:29620499). However, unable to support secretion of the substrate protein EsxC (PubMed:29620499). Homooligomer (PubMed:26785823, PubMed:27723728). Interacts with EsaE (PubMed:27723728). Loss of secretion of EsxA and EsxC but not their expression (PubMed:27130157). Belongs to the EssC family.