Fig. 1

MBE biosynthesis in E. coli RQ1. Overexpression of native PrpE and heterologous PCC complex from S. coelicolor leads to the production of extender unit methylmalonyl-CoA from exogenous propionate. FadD28 allows loading of free FA (FFA) onto KS domain of Mas via its conversion into acyl-AMP derivatives. To be active, Mas must be post-translationally modified by B. subtilis phosphopantetheinyl transferase Sfp. Once modified, Mas is able to elongate the acyl group loaded on its KS domain using methylmalonyl-CoA as extender unit through four iterative catalytic cycles. Finally, PapA5 catalyzes a transesterification reaction between the enzyme-linked multimethyl-branched FA and exogenous n-octanol, giving rise to MBE. Gray ovals indicate protein expression from genome insertions. White ovals indicate protein expression from plasmids. All protein-coding genes referred in this scheme are under the control of T7 promoters