Figure 1. MmpL3 is essential for mycobacterial physiology and is an attractive target for anti-TB drugs.

(a) Schematic representation of the Mtb cell envelope. The cell envelope is composed of an inner membrane, a cell wall (peptidoglycan, arabinogalactan and mycomembrane), and a capsule. MmpL3 is involved in TMM transport across the inner membrane. TMM is the precursor for lipids that make up the outer membrane. Once in the periplasm, TMM gets transported through the periplasm by a chaperone to the outer membrane. At the outer membrane, Ag85 transfers a mycolic acid chain from one TMM to another TMM to synthesise TDM or to yield mycolyl arabinogalactan peptidoglycan. (b) Chemical structures of TMM, PE and inhibitors targeting mycolic acid biosynthesis.