FIGURE 4.

Chimeric trimodular PKSs. Each PKS includes LDD(4), DEBS (5)M1(2), a variable (3)Module(2), and DEBS (3)M3+TE as the terminal module. The variable intervening modules were derived from DEBS, RIFS, or RAPS. Compatible docking domains from DEBS (depicted as black tabs or numbers in parentheses) were fused to the C and N termini of each module. The predicted triketide products 9–15, generated in the presence of propionyl-CoA, methylmalonyl-CoA (and malonyl-CoA, in the case of RIFS M2+TE), and NADPH, are shown above each trimodular combination. All acceptor modules were specific for methylmalonyl-CoA except for RIFS M2, which prefers malonyl-CoA but can also accept methylmalonyl-CoA.