 As shown in Figure 1, MLSB (1.2 MDa) contains seven consecutive extension modules and MLSA 1 (1.8 MDa) consists of eight.The remaining PKS enzyme, MLSA 2, contains the ninth module of MLSA.The C-terminal domains of both MLSA2 and MLSB includes a thioesterase (TE) that was thought to catalyze the formation of the mycolactone core but appears inactive.