MYCOLIC ACID TRANSPORT IN MYCOBACTERIA

Abstract

The mycobacterial cell envelope consists of two membranes, an inner membrane (IM) and a mycolic acid-rich outer membrane (OM). The OM is an exceptional permeability barrier and is essential for virulence. As the major lipid component of the OM, mycolic acids are biosynthesized as trehalose monomycolates (TMMs) in the IM and then transported across the IM, the aqueous periplasm and finally to the OM. In this thesis, we set out to characterize the function of MmpL3, which is implicated in TMM transport, but its exact function has not been elucidated. We developed two biochemical functional assays in M. smegmatis spheroplasts, as well as in MmpL3 inserted protoliposome, to monitor the TMM topology in membrane. We demonstrated that MmpL3 is the TMM flippase and BM212, a putative MmpL3 inhibitor, targets MmpL3 directly. In addition, we seek the TMM chaperone by several biochemical assays and found Ag85 could be the candidate.