Part of the ESX-1 / type VII specialized secretion system (T7SS), which exports several proteins including EsxA and EsxB (PubMed:18554329). Plays a role in DNA conjugation, in both donor and recipient strains (PubMed:18554329). Part of the ESX-1 / type VII secretion system (T7SS), which is composed of cytosolic and membrane components. The ESX-1 membrane complex is composed of EccB1, EccCa1, EccCb1, EccD1 and EccE1 (By similarity). Loss of DNA conjugation when disrupted in recipient strain, strain does not secrete EsxB (PubMed:18554329). DNA conjugation in M.smegmatis is unidirectional with distinct donor and recipient strains; mc(2)155 is a donor strain while MKD8 is a recipient strain. Mutations in a donor strain that alter DNA transfer do not always alter DNA transfer in a recipient strain.