title: Acyl-chain elongation drives ketosynthase substrate selectivity in trans-acyltransferase polyketide synthases.
abstract: Type I modular polyketide synthases (PKSs), which are responsible for the biosynthesis of many biologically active agents, possess a ketosynthase (KS) domain within each module to catalyze chain elongation. Acylation of the KS active site Cys residue is followed by transfer to malonyl-ACP to yield an extended β-ketoacyl chain (ACP = acyl carrier protein). To date, the precise contribution of KS selectivity in controlling product fidelity has been unclear. Six KS domains from trans-acyltransferase (trans-AT) PKSs were subjected to a mass spectrometry based elongation assay, and higher substrate selectivity was identified for the elongating step than in preceding acylation. A close correspondence between the observed KS selectivity and that predicted by phylogenetic analysis was seen. These findings provide insights into the mechanism of KS selectivity in this important group of PKSs, can serve as guidance for engineering, and show that targeted mutagenesis can be used to expand the repertoire of acceptable substrates.
authors.affiliation: School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD (UK).
authors.forename: Matthew
authors.initials: M
authors.lastname: Jenner
authors.forename: José Pedro
authors.initials: JP
authors.lastname: Afonso
authors.forename: Hannah R
authors.initials: HR
authors.lastname: Bailey
authors.forename: Sarah
authors.initials: S
authors.lastname: Frank
authors.forename: Annette
authors.initials: A
authors.lastname: Kampa
authors.forename: Jörn
authors.initials: J
authors.lastname: Piel
authors.forename: Neil J
authors.initials: NJ
authors.lastname: Oldham
mesh_terms: D000217:Acyltransferases / Q000378:metabolism*; D048630:Polyketide Synthases / Q000378:metabolism*; D013379:Substrate Specificity; D053719:Tandem Mass Spectrometry
chemical_list: D048630:Polyketide Synthases; D000217:Acyltransferases
keywords: biosynthesis; ketosynthases; mass spectrometry; polyketide synthases; polyketides