title: Inversion of Extender Unit Selectivity in the Erythromycin Polyketide Synthase by Acyltransferase Domain Engineering.
abstract: Acyltransferase (AT) domains of polyketide synthases (PKSs) select extender units for incorporation into polyketides and dictate large portions of the structures of clinically relevant natural products. Accordingly, there is significant interest in engineering the substrate specificity of PKS ATs in order to site-selectively manipulate polyketide structure. However, previous attempts to engineer ATs have yielded mutant PKSs with relaxed extender unit specificity, rather than an inversion of selectivity from one substrate to another. Here, by directly screening the extender unit selectivity of mutants from active site saturation libraries of an AT from the prototypical PKS, 6-deoxyerythronolide B synthase, a set of single amino acid substitutions was discovered that dramatically impact the selectivity of the PKS with only modest reductions of product yields. One particular substitution (Tyr189Arg) inverted the selectivity of the wild-type PKS from its natural substrate toward a non-natural alkynyl-modified extender unit while maintaining more than twice the activity of the wild-type PKS with its natural substrate. The strategy and mutations described herein form a platform for combinatorial biosynthesis of site-selectively modified polyketide analogues that are modified with non-natural and non-native chemical functionality.
authors.affiliation: Department of Chemistry, NC State University , Raleigh, North Carolina 27695-8204, United States.
authors.forename: Irina
authors.initials: I
authors.lastname: Koryakina
authors.affiliation: Department of Chemistry, NC State University , Raleigh, North Carolina 27695-8204, United States.
authors.forename: Christian
authors.initials: C
authors.lastname: Kasey
authors.forename: John B
authors.initials: JB
authors.lastname: McArthur
authors.affiliation: Life Sciences Institute, Department of Medicinal Chemistry, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Lowell
authors.affiliation: Life Sciences Institute, Department of Medicinal Chemistry, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Chemler
authors.affiliation: Life Sciences Institute, Department of Medicinal Chemistry, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors.forename: Shasha
authors.initials: S
authors.lastname: Li
authors.affiliation: Life Sciences Institute, Department of Medicinal Chemistry, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors.forename: Douglas A
authors.identifier: 0000-0003-4681-650X
authors.initials: DA
authors.lastname: Hansen
authors.affiliation: Life Sciences Institute, Department of Medicinal Chemistry, University of Michigan , Ann Arbor, Michigan 48109, United States.|Department of Chemistry, Department of Microbiology & Immunology, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors.forename: David H
authors.initials: DH
authors.lastname: Sherman
authors.affiliation: Department of Chemistry, NC State University , Raleigh, North Carolina 27695-8204, United States.
authors.forename: Gavin J
authors.identifier: 0000-0003-2172-9063
authors.initials: GJ
authors.lastname: Williams
mesh_terms: D000217:Acyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004917:Erythromycin / Q000737:chemistry / Q000378:metabolism*; D018942:Macrolides / Q000737:chemistry / Q000378:metabolism; D016297:Mutagenesis, Site-Directed / Q000379:methods; D017354:Point Mutation; D048630:Polyketide Synthases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D061065:Polyketides / Q000737:chemistry / Q000378:metabolism*; D000072417:Protein Domains; D016930:Saccharopolyspora / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D018942:Macrolides; D061065:Polyketides; D004917:Erythromycin; D048630:Polyketide Synthases; C079477:10-deoxymethynolide; D000217:Acyltransferases