Primary Citation of Related Structures:   5ACN, 6ACN
PubMed Abstract: 
The structure of activated pig heart aconitase [citrate(isocitrate) hydro-lyase, EC 4.2.1.3] containing a [4Fe-4S] cluster has been refined at 2.5-A resolution to a crystallographic residual of 18.2%. Comparison of this structure to the recently determined 2 ...
The structure of activated pig heart aconitase [citrate(isocitrate) hydro-lyase, EC 4.2.1.3] containing a [4Fe-4S] cluster has been refined at 2.5-A resolution to a crystallographic residual of 18.2%. Comparison of this structure to the recently determined 2.1-A resolution structure of the inactive enzyme containing a [3Fe-4S] cluster, by difference Fourier analysis, shows that upon activation iron is inserted into the structure isomorphously. The common atoms of the [3Fe-4S] and [4Fe-4S] cores agree within 0.1 A; the three common cysteinyl S gamma ligand atoms agree within 0.25 A. The fourth ligand of the Fe inserted into the [3Fe-4S] cluster is a water or hydroxyl from solvent, consistent with the absence of a free cysteine ligand in the enzyme active site cleft and the isomorphism of the two structures. A water molecule occupies a similar site in the crystal structure of the inactive enzyme.
Related Citations: 
The Structure of Aconitase Robbins, A.H., Stout, C.D. (1989) Proteins 5: 289
Iron-Sulfur Cluster in Aconitase. Crystallographic Evidence for a Three-Iron Center Robbins, A.H., Stout, C.D. (1985) J Biol Chem 260: 2328
Organizational Affiliation: 
Department of Molecular Biology, Research Institute of Scripps Clinic, La Jolla, CA 92037.