The crystal structure of the iron free (Apo-)form of Stearoyl Acyl Carrier Protein Desaturase from Ricinus Communis (Castor Bean).

Experimental Data Snapshot

  • Resolution: 3.20 Å
  • R-Value Free: 0.257 
  • R-Value Work: 0.229 
  • R-Value Observed: 0.229 

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Azide and Acetate Complexes plus two iron-depleted Crystal Structures of the Di-iron Enzyme delta9 Stearoyl-ACP Desaturase-Implications for Oxygen Activation and Catalytic Intermediates

Moche, M.Shanklin, J.Ghoshal, A.Lindqvist, Y.

(2003) J Biol Chem 278: 25072-25080

  • DOI: https://doi.org/10.1074/jbc.M301662200
  • Primary Citation of Related Structures:  
    1OQ4, 1OQ7, 1OQ9, 1OQB

  • PubMed Abstract: 

    Delta9 stearoyl-acyl carrier protein (ACP) desaturase is a mu-oxo-bridged di-iron enzyme, which belongs to the structural class I of large helix bundle proteins and that catalyzes the NADPH and O2-dependent formation of a cis-double bond in stearoyl-ACP. The crystal structures of complexes with azide and acetate, respectively, as well as the apoand single-iron forms of Delta9 stearoyl-ACP desaturase from Ricinus communis have been determined. In the azide complex, the ligand forms a mu-1,3-bridge between the two iron ions in the active site, replacing a loosely bound water molecule. The structure of the acetate complex is similar, with acetate bridging the di-iron center in the same orientation with respect to the di-iron center. However, in this complex, the iron ligand Glu196 has changed its coordination mode from bidentate to monodentate, the first crystallographic observation of a carboxylate shift in Delta9 stearoyl-ACP desaturase. The two complexes are proposed to mimic a mu-1,2 peroxo intermediate present during catalytic turnover. There are striking structural similarities between the di-iron center in the Delta9 stearoyl-ACP desaturase-azide complex and in the reduced rubrerythrin-azide complex. This suggests that Delta9 stearoyl-ACP desaturase might catalyze the formation of water from exogenous hydrogen peroxide at a low rate. From the similarity in iron center structure, we propose that the mu-oxo-bridge in oxidized desaturase is bound to the di-iron center as in rubrerythrin and not as reported for the R2 subunit of ribonucleotide reductase and the hydroxylase subunit of methane monooxygenase. The crystal structure of the one-iron depleted desaturase species demonstrates that the affinities for the two iron ions comprising the di-iron center are not equivalent, Fe1 being the higher affinity site and Fe2 being the lower affinity site.

  • Organizational Affiliation

    Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm S-171 77, Sweden.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Acyl-[acyl-carrier protein] desaturase
A, B, C, D, E
A, B, C, D, E, F
363Ricinus communisMutation(s): 0 
Find proteins for P22337 (Ricinus communis)
Explore P22337 
Go to UniProtKB:  P22337
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP22337
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 3.20 Å
  • R-Value Free: 0.257 
  • R-Value Work: 0.229 
  • R-Value Observed: 0.229 
  • Space Group: P 31
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 188.033α = 90
b = 188.033β = 90
c = 82.047γ = 120
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2003-05-13
    Type: Initial release
  • Version 1.1: 2008-04-29
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2023-10-25
    Changes: Data collection, Database references, Derived calculations, Refinement description