Mycobacterium tuberculosis (Mtb) is the etiologic pathogen of tuberculosis (TB), the leading infectious cause of death. Mtb is a diderm bacillus that is exquisitely well-adapted to its human host. In this work, we identify the lipoprotein LpqN as a periplasmic interacting partner of the mycolate transporters MmpL3 and MmpL11, and of secreted mycolyltransferases. Together, this work furthers our understanding of the bacterial physiology underlying the biogenesis of the mycobacterial cell envelope, perhaps the most critical interface between the host and pathogen.