Contributes to evasion of both innate and adaptive immunity. Inhibits autophagy in infected host phagocytes and inhibits major histocompatibility complex (MHC) class II antigen presentation by mycobacteria-infected dendritic cells. Has an important role in the growth and survival of M.tuberculosis, particularly during intracellular growth and in the later chronic phase of infection. Loosely attached to the cell surface, with the potential to detach during growth within infected cells. Deletion mutant is attenuated in vitro and in vivo, and shows enhanced MHC class II-restricted antigen presentation during in vivo infection of mice. Also shows a reduced capability to inhibit autophagy and an increased acidification and lysosomal fusion of phagosomes during infection of phagocytic cells. Belongs to the mycobacterial PE family. PGRS subfamily.