Specific chaperone for cognate PE/PPE proteins. Plays an important role in preventing aggregation of PE/PPE dimers. Interacts specifically with ESX-1-dependent PE/PPE proteins (By similarity). Interacts with PPE68 (PubMed:17433643). Inactivation leads to the attenuation of the recombinant strain, in spite of strong EsxA (ESAT-6) secretion and generation of specific T-cell responses. Mutant has lower amounts of PPE68. Belongs to the EspG family.