(12e) Engineering a Synthetic Malonyl-CoA Controller for Dynamic Tuning of Metabolic Flux in E. Coli

Natural biological systems use a lot of negative and positive feedback controls to coordinate gene expression and achieve optimal biological functions. As heterologous pathways become larger and more complicated, it becomes increasingly difficult to optimize them with static regulatory control. An ideal approach would be to use dynamic regulatory networks to control gene expression so that the host cells can adjust their metabolic functions when the environmental condition changes. Here we report engineering both the positive and negative feedback controls for dynamic tuning of metabolic flux in E. coli. We have identified a dual transcriptional regulator which can act either as an activator or a repressor for two different promoters. The level of activation or repression is dependent on the level of intracellular malonyl-CoA. As a proof of concept, we demonstrated that the expression of two reporter proteins can be exclusively switched between the on and off state. By engineering this synthetic malonyl-CoA controller, we envision that both the malonyl-CoA source pathway and the malonyl-CoA sink pathway can be dynamically modulated so that carbon flux can be efficiently redirected to synthesize our target compounds. Implementation of this dynamic control will maintain the intracellular malonyl-CoA at the optimal level and improve both the productivity and yield of value-added metabolites in E. coli.