A conserved motif flags acyl carrier proteins for β-branching in polyketide synthesis

Research output: Contribution to journalArticlepeer-review


  • Xu Dong
  • Zhongshu Song
  • Rohit Farmer
  • Christopher Williams
  • Eliza Płoskoń
  • Pakorn Wattana-amorn
  • Elton R Stephens
  • Erika Yamada
  • Rachel Gurney
  • Yuiko Takebayashi
  • Joleen Masschelein
  • Russell J Cox
  • Rob Lavigne
  • Christine L Willis
  • Thomas J Simpson
  • John Crosby
  • Matthew P Crump

Colleges, School and Institutes


Type I polyketide synthases often use programmed β-branching, via enzymes of a 'hydroxymethylglutaryl-CoA synthase (HCS) cassette', to incorporate various side chains at the second carbon from the terminal carboxylic acid of growing polyketide backbones. We identified a strong sequence motif in acyl carrier proteins (ACPs) where β-branching is known to occur. Substituting ACPs confirmed a correlation of ACP type with β-branching specificity. Although these ACPs often occur in tandem, NMR analysis of tandem β-branching ACPs indicated no ACP-ACP synergistic effects and revealed that the conserved sequence motif forms an internal core rather than an exposed patch. Modeling and mutagenesis identified ACP helix III as a probable anchor point of the ACP–HCS complex whose position is determined by the core. Mutating the core affects ACP functionality, whereas ACP-HCS interface substitutions modulate system specificity. Our method for predicting β-carbon branching expands the potential for engineering new polyketides and lays a basis for determining specificity rules.


Original languageEnglish
Pages (from-to)685-692
Number of pages8
JournalNature Chemical Biology
Issue number11
Early online date22 Sep 2013
Publication statusPublished - Nov 2013