Part of the ESX-1 / type VII specialized secretion system (T7SS), which exports several proteins including EsxA and EsxB (PubMed:15687187). Plays a role in DNA conjugation, in both donor and recipient strains (PubMed:15314236). 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). Localizes at or near the cell pole in (on average) 1 discrete spot that also colocalizes with SaeC. Localization requires SaeC and other ESX-1 proteins and can be conferred by the ESX-1 locus of M.tuberculosis (PubMed:22233444). Increases efficiency of DNA conjugation when disrupted in donor strain (PubMed:15314236). Loss of secretion of EsxA and EsxB, but not their expression (PubMed:15687187). 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.