Part of the ESX-1 / type VII specialized secretion system (T7SS), which exports several proteins including EsxA and EsxB (By similarity). Specific chaperone for cognate PE/PPE proteins, plays an important role in preventing aggregation of PE/PPE dimers (By similarity). Also plays a role in DNA conjugation, in at least recipient strain (PubMed:18554329). Interacts specifically with ESX-1-dependent PE/PPE proteins (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. Belongs to the EspG family.