Engineered Biosynthesis of Alkyne-Tagged Polyketides by Type I PKSs

Abstract

Polyketides produced by modular polyketide synthases are important small molecules widely used as drugs, pesticides, herbicides and biological probes. Tagging these polyketides with a clickable functionality enables the visualization, diversification and mode of action study through bio-orthogonal chemistry and is thus actively pursued with multiple tagging strategies reported. We here report the first de novo biosynthesis of alkyne-tagged polyketides by modular type I PKSs through starter unit engineering. Specifically, using JamABC, a carrier protein-dependent terminal alkyne biosynthetic machinery from jamaicamide B biosynthetic pathway, and representative modular PKSs from lipomycin and erythromycin biosynthetic pathways, we show that JamABC works as a trans loading system for engineered Type I PKSs to produce alkyne-tagged polyketides both in vitro and in vivo. In addition, the production efficiency can be improved by enhancing the interactions between the carrier protein (JamC) and PKSs using docking domains and site-directed mutagenesis of JamC. This work thus provides engineering guidelines and strategies which are applicable to additional modular Type I PKSs to produce targeted alkyne-tagged metabolites for chemical and biological applications.