Structural Basis of Polyketide Synthase O-Methylation.

ABSTRACT: Modular type I polyketide synthases (PKSs) produce some of the most chemically complex metabolites in nature through a series of multienzyme modules. Each module contains a variety of catalytic domains to selectively tailor the growing molecule. PKS O-methyltransferases ( O-MTs) are predicted to methylate ?-hydroxyl or ?-keto groups, but their activity and structure have not been reported. We determined the domain boundaries and characterized the catalytic activity and structure of the StiD and StiE O-MTs, which methylate opposite ?-hydroxyl stereocenters in the myxobacterial stigmatellin biosynthetic pathway. Substrate stereospecificity was demonstrated for the StiD O-MT. Key catalytic residues were identified in the crystal structures and investigated in StiE O-MT via site-directed mutagenesis and further validated with the cyanobacterial CurL O-MT from the curacin biosynthetic pathway. Initial structural and biochemical analysis of PKS O-MTs supplies a new chemoenzymatic tool, with the unique ability to selectively modify hydroxyl groups during polyketide biosynthesis.

SUBMITTER: Skiba MA 

PROVIDER: S-EPMC6470024 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature