Gene Conversion Directed Successive Engineering of Modular Polyketide Synthases

Abstract

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 novel 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 novel macrolide with predicted structural features. Moreover, in contrast to previous notion, the intra-module KS domain is demonstrated to associate with the selectivity of extender units. Collectively, the coordination between evolutionary consequence and functional manipulation of assembly line may shed a new light on modular PKS engineering. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=104 SRC="FIGDIR/small/630704v1_ufig1.gif" ALT="Figure 1"> View larger version (17K): org.highwire.dtl.DTLVardef@11bd249org.highwire.dtl.DTLVardef@18af1a9org.highwire.dtl.DTLVardef@ffa287org.highwire.dtl.DTLVardef@10756cf_HPS_FORMAT_FIGEXP M_FIG Gene conversion process, typically occurred in KS (purple squares) and AT (blue squares), plays an integral role of structural diversity of polyketides. In this study, an unusual gene conversion was observed in cmm BGC. Subsequently, a homologous BGC was obtained through genome mining by a gene conversion-associated KS domain. Under the direction of gene conversion, the modular PKS in cmm BGC was successively reprogrammed, resulting in de novo biosynthesis of a new-to-nature polyketide. C_FIG