The first crystal structure of the DABA aminotransferase EctB in the ectoine biosynthesis pathway of the model organism Chromohalobacter salexigens DSM 3034

Experimental Data Snapshot

  • Resolution: 2.45 Å
  • R-Value Free: 0.243 
  • R-Value Work: 0.185 
  • R-Value Observed: 0.186 

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The crystal structure of the tetrameric DABA-aminotransferase EctB, a rate-limiting enzyme in the ectoine biosynthesis pathway.

Hillier, H.T.Altermark, B.Leiros, I.

(2020) FEBS J 287: 4641-4658

  • DOI: https://doi.org/10.1111/febs.15265
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    l-2,4-diaminobutyric acid (DABA) aminotransferases can catalyze the formation of amines at the distal ω-position of substrates, and is the intial and rate-limiting enzyme in the biosynthesis pathway of the cytoprotecting molecule (S)-2-methyl-1,4,5,6-tetrahydro-4-pyrimidine carboxylic acid (ectoine). Although there is an industrial interest in the biosynthesis of ectoine, the DABA aminotransferases remain poorly characterized. Herein, we present the crystal structure of EctB (2.45 Å), a DABA aminotransferase from Chromohalobacter salexigens DSM 3043, a well-studied organism with respect to osmoadaptation by ectoine biosynthesis. We investigate the enzyme's oligomeric state to show that EctB from C. salexigens is a tetramer of two functional dimers, and suggest conserved recognition sites for dimerization that also includes the characteristic gating loop that helps shape the active site of the neighboring monomer. Although ω-transaminases are known to have two binding pockets to accommodate for their dual substrate specificity, we herein provide the first description of two binding pockets in the active site that may account for the catalytic character of DABA aminotransferases. Furthermore, our biochemical data reveal that the EctB enzyme from C. salexigens is a thermostable, halotolerant enzyme with a broad pH tolerance which may be linked to its tetrameric state. Put together, this study creates a solid foundation for a deeper structural understanding of DABA aminotransferases and opening up for future downstream studies of EctB's catalytic character and its redesign as a better catalyst for ectoine biosynthesis. In summary, we believe that the EctB enzyme from C. salexigens can serve as a benchmark enzyme for characterization of DABA aminotransferases. DATABASE: Structural data are available in PDB database under the accession number 6RL5.

  • Organizational Affiliation

    The Norwegian Structural Biology Centre (NorStruct), Department of Chemistry, Faculty of Science and Technology, UiT the Arctic University of Norway, Tromsø, Norway.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Diaminobutyrate--2-oxoglutarate transaminase
A, B, C, D, E
A, B, C, D, E, F, G, H
429Chromohalobacter salexigens DSM 3043Mutation(s): 0 
Gene Names: ectBCsal_1877
Find proteins for Q9ZEU7 (Chromohalobacter salexigens (strain ATCC BAA-138 / DSM 3043 / CIP 106854 / NCIMB 13768 / 1H11))
Explore Q9ZEU7 
Go to UniProtKB:  Q9ZEU7
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ9ZEU7
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.45 Å
  • R-Value Free: 0.243 
  • R-Value Work: 0.185 
  • R-Value Observed: 0.186 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 107.055α = 90
b = 124.782β = 98.95
c = 145.416γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
XSCALEdata scaling
Aimlessdata scaling
Cootmodel building

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2020-03-11
    Type: Initial release
  • Version 1.1: 2020-11-11
    Changes: Database references