A polyketide synthase acyltransferase domain structure suggests a recognition mechanism for its hydroxymalonyl-acyl carrier protein substrate

PLoS One. 2014 Oct 23;9(10):e110965. doi: 10.1371/journal.pone.0110965. eCollection 2014.


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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Acyl Carrier Protein / chemistry*
  • Acyltransferases / chemistry*
  • Amino Acid Motifs
  • Bacillus cereus / enzymology*
  • Bacterial Proteins / chemistry*
  • Catalytic Domain
  • Cloning, Molecular
  • Crystallography, X-Ray
  • Multienzyme Complexes / chemistry
  • Peptides
  • Polyketide Synthases / chemistry
  • Protein Engineering
  • Protein Structure, Tertiary
  • Substrate Specificity
  • Tartronates / chemistry*


  • Acyl Carrier Protein
  • Bacterial Proteins
  • Multienzyme Complexes
  • Peptides
  • Tartronates
  • zwittermicin A
  • Polyketide Synthases
  • Acyltransferases

Associated data

  • PDB/4QBU