A crotonyl-CoA reductase-carboxylase independent pathway for assembly of unusual alkylmalonyl-CoA polyketide synthase extender units

Lauren Ray, Timothy R. Valentic, Takeshi Miyazawa, David M. Withall, Lijiang Song, Jacob C. Milligan, Hiroyuki Osada, Shunji Takahashi, Shiou Chuan Tsai, Gregory L. Challis

Research output: Contribution to journalArticleResearchpeer-review

11 Citations (Scopus)

Abstract

Type I modular polyketide synthases assemble diverse bioactive natural products. Such multienzymes typically use malonyl and methylmalonyl-CoA building blocks for polyketide chain assembly. However, in several cases more exotic alkylmalonyl-CoA extender units are also known to be incorporated. In all examples studied to date, such unusual extender units are biosynthesized via reductive carboxylation of α, β-unsaturated thioesters catalysed by crotonyl-CoA reductase/carboxylase (CCRC) homologues. Here we show using a chemically-synthesized deuterium-labelled mechanistic probe, and heterologous gene expression experiments that the unusual alkylmalonyl-CoA extender units incorporated into the stambomycin family of polyketide antibiotics are assembled by direct carboxylation of medium chain acyl-CoA thioesters. X-ray crystal structures of the unusual β-subunit of the acyl-CoA carboxylase (YCC) responsible for this reaction, alone and in complex with hexanoyl-CoA, reveal the molecular basis for substrate recognition, inspiring the development of methodology for polyketide bio-orthogonal tagging via incorporation of 6-azidohexanoic acid and 8-nonynoic acid into novel stambomycin analogues.

Original languageEnglish
Article number13609
Number of pages12
JournalNature Communications
Volume7
DOIs
Publication statusPublished - 21 Dec 2016
Externally publishedYes

Keywords

  • biosynthesis
  • multienzyme complexes

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