Experimental Data Snapshot

  • Resolution: 2.30 Å
  • R-Value Free: 0.238 
  • R-Value Work: 0.212 
  • R-Value Observed: 0.212 

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Human ornithine aminotransferase complexed with L-canaline and gabaculine: structural basis for substrate recognition.

Shah, S.A.Shen, B.W.Brunger, A.T.

(1997) Structure 5: 1067-1075

  • DOI: https://doi.org/10.1016/s0969-2126(97)00258-x
  • Primary Citation of Related Structures:  
    1GBN, 2CAN

  • PubMed Abstract: 

    Ornithine aminotransferase (OAT) is a 45 kDa pyridoxal-5'-phosphate (PLP)-dependent enzyme that catalyzes the conversion of L-ornithine and 2-oxoglutarate to glutamate-delta-semialdehyde and glutamic acid, respectively. In humans, loss of OAT function causes an accumulation of ornithine that results in gyrate atrophy of the choroid and retina, a disease that progressively leads to blindness. In an effort to learn more about the structural basis of this enzyme's function, we have determined the X-ray structures of OAT in complex with two enzyme-activated suicide substrates: L-canaline, an ornithine analog, and gabaculine, an irreversible inhibitor of several related aminotransferases. The structures of human OAT bound to the inhibitors gabaculine and L-canaline were solved to 2.3 A at 110K by difference Fourier techniques. Both inhibitors coordinate similarly in the active site, binding covalently to the PLP cofactor and causing a 20 degrees rotation in the cofactor tilt relative to the ligand-free form. Aromatic-aromatic interactions occur between the bound gabaculine molecule and active-site residues Tyr85 and Phe177, whereas Tyr55 and Arg180 provide specific contacts to the alpha-amino and carboxyl groups of L-canaline. The OAT-L-canaline complex structure implicates Tyr55 and Arg180 as the residues involved in coordinating with the natural substrate ornithine during normal enzyme turnover. This correlates well with two enzyme-inactivating point mutations associated with gyrate atrophy, Tyr55-->His and Arg180-->Thr. The OAT-gabaculine complex provides the first structural evidence that the potency of the inhibitor is due to energetically favourable aromatic interactions with residues in the active site. This aromatic-binding mode may be relevant to structure-based drug design efforts against other omega-aminotransferase targets, such as GABA aminotransferase.

  • Organizational Affiliation

    Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B, C
402Homo sapiensMutation(s): 0 
UniProt & NIH Common Fund Data Resources
Find proteins for P04181 (Homo sapiens)
Explore P04181 
Go to UniProtKB:  P04181
PHAROS:  P04181
GTEx:  ENSG00000065154 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP04181
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.30 Å
  • R-Value Free: 0.238 
  • R-Value Work: 0.212 
  • R-Value Observed: 0.212 
  • Space Group: P 32 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 115.915α = 90
b = 115.915β = 90
c = 185.729γ = 120
Software Package:
Software NamePurpose
X-PLORmodel building
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

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Ligand Structure Quality Assessment 

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 1998-06-03
    Type: Initial release
  • Version 1.1: 2008-03-03
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Derived calculations, Version format compliance
  • Version 1.3: 2023-08-09
    Changes: Database references, Derived calculations, Other, Refinement description
  • Version 1.4: 2024-05-22
    Changes: Data collection