Distinct structural elements dictate the specificity of the type III pentaketide synthase from Neurospora crassa

Chem Biol. 2008 Oct 20;15(10):1079-90. doi: 10.1016/j.chembiol.2008.08.011.


The fungal type III polyketide synthase 2'-oxoalkylresorcylic acid synthase (ORAS) primes with a range of acyl-Coenzyme A thioesters (C4-C20) and extends using malonyl-Coenzyme A to produce pyrones, resorcinols, and resorcylic acids. To gain insight into this unusual substrate specificity and product profile, we have determined the crystal structures of ORAS to 1.75 A resolution, the Phe-252-->Gly site-directed mutant to 2.1 A resolution, and a binary complex of ORAS with eicosanoic acid to 2.0 A resolution. The structures reveal a distinct rearrangement of structural elements near the active site that allows accommodation of long-chain fatty acid esters and a reorientation of the gating mechanism that controls cyclization and polyketide chain length. The roles of these structural elements are further elucidated by characterization of various structure-based site-directed variants. These studies establish an unexpected plasticity to the PKS fold, unanticipated from structural studies of other members of this enzyme family.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Catalytic Domain
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Genes, Reporter / genetics
  • Macrolides / chemistry
  • Macrolides / metabolism
  • Models, Molecular
  • Molecular Sequence Data
  • Mutation / genetics
  • Neurospora crassa / enzymology*
  • Polyketide Synthases / chemistry*
  • Polyketide Synthases / classification
  • Polyketide Synthases / genetics
  • Polyketide Synthases / metabolism*
  • Protein Binding
  • Protein Structure, Quaternary
  • Protein Structure, Tertiary
  • Sequence Alignment
  • Substrate Specificity


  • Macrolides
  • Polyketide Synthases

Associated data

  • PDB/3EUO
  • PDB/3EUQ
  • PDB/3EUT