Specific chaperone for cognate PE/PPE proteins. Plays an important role in preventing aggregation of PE/PPE dimers. Required for LipY and PE31/PPE18 secretion. Interacts specifically with ESX-5-dependent PE/PPE proteins. Binds PPE33 and PPE18. Does not interact with EsxN. Monomer in solution. Belongs to the EspG family.