Illuminating the catalytic core of ectoine synthase through structural and biochemical analysis

Sci Rep. 2019 Jan 23;9(1):364. doi: 10.1038/s41598-018-36247-w.


Ectoine synthase (EctC) is the signature enzyme for the production of ectoine, a compatible solute and chemical chaperone widely synthesized by bacteria as a cellular defense against the detrimental effects of osmotic stress. EctC catalyzes the last step in ectoine synthesis through cyclo-condensation of the EctA-formed substrate N-gamma-acetyl-L-2,4-diaminobutyric acid via a water elimination reaction. We have biochemically and structurally characterized the EctC enzyme from the thermo-tolerant bacterium Paenibacillus lautus (Pl). EctC is a member of the cupin superfamily and forms dimers, both in solution and in crystals. We obtained high-resolution crystal structures of the (Pl)EctC protein in forms that contain (i) the catalytically important iron, (ii) iron and the substrate N-gamma-acetyl-L-2,4-diaminobutyric acid, and (iii) iron and the enzyme reaction product ectoine. These crystal structures lay the framework for a proposal for the EctC-mediated water-elimination reaction mechanism. Residues involved in coordinating the metal, the substrate, or the product within the active site of ectoine synthase are highly conserved among a large group of EctC-type proteins. Collectively, the biochemical, mutational, and structural data reported here yielded detailed insight into the structure-function relationship of the (Pl)EctC enzyme and are relevant for a deeper understanding of the ectoine synthase family as a whole.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Substitution
  • Amino Acids, Diamino / chemistry*
  • Binding Sites
  • Catalytic Domain*
  • Hydro-Lyases / chemistry*
  • Hydro-Lyases / isolation & purification
  • Iron / chemistry
  • Models, Molecular*
  • Molecular Docking Simulation
  • Molecular Dynamics Simulation
  • Protein Binding
  • Protein Multimerization
  • Recombinant Proteins
  • Structure-Activity Relationship
  • Substrate Specificity


  • Amino Acids, Diamino
  • Recombinant Proteins
  • ectoine
  • Iron
  • Hydro-Lyases
  • ectoine synthase