title: A polyketide synthase acyltransferase domain structure suggests a recognition mechanism for its hydroxymalonyl-acyl carrier protein substrate.
abstract: We have previously shown that the acyl transferase domain of ZmaA (ZmaA-AT) is involved in the biosynthesis of the aminopolyol polyketide/nonribosomal peptide hybrid molecule zwittermicin A from cereus UW85, and that it specifically recognizes the precursor hydroxymalonyl-acyl carrier protein (ACP) and transfers the hydroxymalonyl extender unit to a downstream second ACP via a transacylated AT domain intermediate. We now present the X-ray crystal structure of ZmaA-AT at a resolution of 1.7 Å. The structure shows a patch of solvent-exposed hydrophobic residues in the area where the AT is proposed to interact with the precursor ACP. We addressed the significance of the AT/ACP interaction in precursor specificity of the AT by testing whether malonyl- or methylmalonyl-ACP can be recognized by ZmaA-AT. We found that the ACP itself biases extender unit selection. Until now, structural information for ATs has been limited to ATs specific for the CoA-linked precursors malonyl-CoA and (2S)-methylmalonyl-CoA. This work contributes to polyketide synthase engineering efforts by expanding our knowledge of AT/substrate interactions with the structure of an AT domain that recognizes an ACP-linked substrate, the rare hydroxymalonate. Our structure suggests a model in which ACP interaction with a hydrophobic motif promotes secondary structure formation at the binding site, and opening of the adjacent substrate pocket lid to allow extender unit binding in the AT active site.
authors.affiliation: Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
authors.forename: Hyunjun
authors.initials: H
authors.lastname: Park
authors.affiliation: Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
authors.forename: Brian M
authors.initials: BM
authors.lastname: Kevany
authors.affiliation: Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
authors.forename: David H
authors.initials: DH
authors.lastname: Dyer
authors.affiliation: Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Thomas
authors.affiliation: Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
authors.forename: Katrina T
authors.initials: KT
authors.lastname: Forest
mesh_terms: D000213:Acyl Carrier Protein / Q000737:chemistry*; D000217:Acyltransferases / Q000737:chemistry*; D020816:Amino Acid Motifs; D001409:Bacillus cereus / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry*; D020134:Catalytic Domain; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D009097:Multienzyme Complexes / Q000737:chemistry; D010455:Peptides; D048630:Polyketide Synthases / Q000737:chemistry; D015202:Protein Engineering; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity; D013646:Tartronates / Q000737:chemistry*
chemical_list: D000213:Acyl Carrier Protein; D001426:Bacterial Proteins; D009097:Multienzyme Complexes; D010455:Peptides; D013646:Tartronates; C088290:zwittermicin A; D048630:Polyketide Synthases; D000217:Acyltransferases