Crystal structure of halogenase PltA from the pyoluteorin biosynthetic pathway

J Struct Biol. 2015 Dec;192(3):349-357. doi: 10.1016/j.jsb.2015.09.013. Epub 2015 Sep 28.


Pyoluteorin is an antifungal agent composed of a 4,5-dichlorinated pyrrole group linked to a resorcinol moiety. The pyoluteorin biosynthetic gene cluster in Pseudomonas fluorescens Pf-5 encodes the halogenase PltA, which has been previously demonstrated to perform both chlorinations in vitro. PltA selectively accepts as a substrate a pyrrole moiety covalently tethered to a nonribosomal peptide thiolation domain PltL (pyrrolyl-S-PltL) for FAD-dependent di-chlorination, yielding 4,5-dichloropyrrolyl-S-PltL. We report a 2.75 Å-resolution crystal structure of PltA in complex with FAD and chloride. PltA is a dimeric enzyme, containing a flavin-binding fold conserved in flavin-dependent halogenases and monooxygenases, and an additional unique helical region at the C-terminus. This C-terminal region blocks a putative substrate-binding cleft, suggesting that a conformational change involving repositioning of this region is necessary to allow binding of the pyrrolyl-S-PltL substrate for its dichlorination by PltA.

Keywords: Chlorination; FAD; Flavoprotein; Halogenation; Natural product.

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

  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / ultrastructure*
  • Binding Sites
  • Chlorine / chemistry*
  • Crystallography, X-Ray
  • Flavin-Adenine Dinucleotide / chemistry*
  • Halogenation / physiology*
  • Models, Molecular
  • Oxidation-Reduction
  • Oxidoreductases / chemistry
  • Phenols / chemistry*
  • Protein Binding / physiology
  • Pseudomonas fluorescens / metabolism
  • Pyrroles / chemistry*


  • Bacterial Proteins
  • Phenols
  • Pyrroles
  • pyoluteorin
  • Flavin-Adenine Dinucleotide
  • Chlorine
  • Oxidoreductases