Gene conversion-associated successive engineering of modular polyketide synthases.

Modular polyketide synthases (PKSs) can produce various secondary metabolites in a collinearity fashion. Although rational engineering of modular PKS can ultimately create a diverse array of compounds, de novo generation of defined structures usually results in the loss or remarkable decline of productivity due primarily to the incompatibility of different elements. Here, we present a modular PKS engineering strategy driven by an evolutionary event of gene conversion to accomplish successive engineering of the modular PKS in cinnamomycin biosynthetic gene cluster (cmm BGC). By simulating the gene conversion process, cmm BGC is consecutively reprogrammed to generate a macrolide with predicted structural features. Moreover, the intra-module KS domain is demonstrated to associate with the proofreading of extender units. Collectively, the gene conversion-associated approach may shed a light on modular PKS engineering.