A crotonyl-CoA reductase-carboxylase independent pathway for assembly of unusual alkylmalonyl-CoA polyketide synthase extender units.Ray, L., Valentic, T.R., Miyazawa, T., Withall, D.M., Song, L., Milligan, J.C., Osada, H., Takahashi, S., Tsai, S.C., Challis, G.L.
(2016) Nat Commun 7: 13609-13609
- PubMed: 28000660
- DOI: 10.1038/ncomms13609
- Primary Citation of Related Structures:
- PubMed 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 exten ...
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.
Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK.