1AFR

STEAROYL-ACYL CARRIER PROTEIN DESATURASE FROM CASTOR SEEDS

Summary for 1AFR

• Entry DOI: 10.2210/pdb1afr/pdb
• Descriptor: DELTA9 STEAROYL-ACYL CARRIER PROTEIN DESATURASE, FE (II) ION (3 entities in total)
• Functional Keywords: oxidoreductase, fatty acid desaturase, fatty acid biosynthesis, binuclear iron center, electron transfer
• Biological source: Ricinus communis (castor bean)
• Total number of polymer chains: 6
• Total formula weight: 239194.58

Authors

Lindqvist, Y.,Huang, W.,Schneider, G. (deposition date: 1997-03-13, release date: 1997-05-15, Last modification date: 2024-02-07)

Primary citation

Lindqvist, Y.,Huang, W.,Schneider, G.,Shanklin, J.
Crystal structure of delta9 stearoyl-acyl carrier protein desaturase from castor seed and its relationship to other di-iron proteins.
EMBO J., 15:4081-4092, 1996

PubMed Abstract: The three-dimensional structure of recombinant homodimeric delta9 stearoyl-acyl carrier protein desaturase, the archetype of the soluble plant fatty acid desaturases that convert saturated to unsaturated fatty acids, has been determined by protein crystallographic methods to a resolution of 2.4 angstroms. The structure was solved by a combination of single isomorphous replacement, anomalous contribution from the iron atoms to the native diffraction data and 6-fold non-crystallographic symmetry averaging. The 363 amino acid monomer consists of a single domain of 11 alpha-helices. Nine of these form an antiparallel helix bundle. The enzyme subunit contains a di-iron centre, with ligands from four of the alpha-helices in the helix bundle. The iron ions are bound in a highly symmetric environment, with one of the irons forming interactions with the side chains of E196 and H232 and the second iron with the side chains of E105 and H146. Two additional glutamic acid side chains, from E143 and E229, are within coordination distance to both iron ions. A water molecule is found within the second coordination sphere from the iron atoms. The lack of electron density corresponding to a mu-oxo bridge, and the long (4.2 angstroms) distance between the iron ions suggests that this probably represents the diferrous form of the enzyme. A deep channel which probably binds the fatty acid extends from the surface into the interior of the enzyme. Modelling of the substrate, stearic acid, into this channel places the delta9 carbon atom in the vicinity of one of the iron ions.

PubMed: 8861937

Experimental method

X-RAY DIFFRACTION (2.4 Å)