Crystal Structure of the Apo ectoine hydroxylase ECTD from Salibacillus salexigens

Experimental Data Snapshot

  • Resolution: 1.78 Å
  • R-Value Free: 0.200 
  • R-Value Work: 0.172 
  • R-Value Observed: 0.173 

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Biochemical properties of ectoine hydroxylases from extremophiles and their wider taxonomic distribution among microorganisms.

Widderich, N.Hoppner, A.Pittelkow, M.Heider, J.Smits, S.H.Bremer, E.

(2014) PLoS One 9: e93809-e93809

  • DOI: https://doi.org/10.1371/journal.pone.0093809
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Ectoine and hydroxyectoine are well-recognized members of the compatible solutes and are widely employed by microorganisms as osmostress protectants. The EctABC enzymes catalyze the synthesis of ectoine from the precursor L-aspartate-β-semialdehyde. A subgroup of the ectoine producers can convert ectoine into 5-hydroxyectoine through a region-selective and stereospecific hydroxylation reaction. This compatible solute possesses stress-protective and function-preserving properties different from those of ectoine. Hydroxylation of ectoine is carried out by the EctD protein, a member of the non-heme-containing iron (II) and 2-oxoglutarate-dependent dioxygenase superfamily. We used the signature enzymes for ectoine (EctC) and hydroxyectoine (EctD) synthesis in database searches to assess the taxonomic distribution of potential ectoine and hydroxyectoine producers. Among 6428 microbial genomes inspected, 440 species are predicted to produce ectoine and of these, 272 are predicted to synthesize hydroxyectoine as well. Ectoine and hydroxyectoine genes are found almost exclusively in Bacteria. The genome context of the ect genes was explored to identify proteins that are functionally associated with the synthesis of ectoines; the specialized aspartokinase Ask_Ect and the regulatory protein EctR. This comprehensive in silico analysis was coupled with the biochemical characterization of ectoine hydroxylases from microorganisms that can colonize habitats with extremes in salinity (Halomonas elongata), pH (Alkalilimnicola ehrlichii, Acidiphilium cryptum), or temperature (Sphingopyxis alaskensis, Paenibacillus lautus) or that produce hydroxyectoine very efficiently over ectoine (Pseudomonas stutzeri). These six ectoine hydroxylases all possess similar kinetic parameters for their substrates but exhibit different temperature stabilities and differ in their tolerance to salts. We also report the crystal structure of the Virgibacillus salexigens EctD protein in its apo-form, thereby revealing that the iron-free structure exists already in a pre-set configuration to incorporate the iron catalyst. Collectively, our work defines the taxonomic distribution and salient biochemical properties of the ectoine hydroxylase protein family and contributes to the understanding of its structure.

  • Organizational Affiliation

    Laboratory for Microbiology, Department of Biology, Philipps-University Marburg, Marburg, Germany; Max Planck Institute for Terrestrial Microbiology, Emeritus Group R.K. Thauer, Marburg, Germany.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
EctD310Virgibacillus salexigensMutation(s): 0 
EC: 1.14.11
Find proteins for Q2TDY4 (Virgibacillus salexigens)
Explore Q2TDY4 
Go to UniProtKB:  Q2TDY4
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ2TDY4
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.78 Å
  • R-Value Free: 0.200 
  • R-Value Work: 0.172 
  • R-Value Observed: 0.173 
  • Space Group: P 65 2 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 102.897α = 90
b = 102.897β = 90
c = 159.66γ = 120
Software Package:
Software NamePurpose
DNAdata collection
XDSdata reduction
XSCALEdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2014-09-10
    Type: Initial release
  • Version 1.1: 2024-02-28
    Changes: Data collection, Database references