1ff2
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CRYSTAL STRUCTURE OF THE C42D MUTANT OF AZOTOBACTER VINELANDII 7FE FERREDOXIN (FDI)
OverviewOverview
All naturally occurring ferredoxins that have Cys-X-X-Asp-X-X-Cys motifs, contain [4Fe-4S](2+/+) clusters that can be easily and reversibly, converted to [3Fe-4S](+/0) clusters. In contrast, ferredoxins with, unmodified Cys-X-X-Cys-X-X-Cys motifs assemble [4Fe-4S](2+/+) clusters, that cannot be easily interconverted with [3Fe-4S](+/0) clusters. In this, study we changed the central cysteine of the, Cys(39)-X-X-Cys(42)-X-X-Cys(45) of Azotobacter vinelandii FdI, which, coordinates its [4Fe-4S](2+/+) cluster, into an aspartate. UV-visible, EPR, and CD spectroscopies, metal analysis, and x-ray crystallography show, that, like native FdI, aerobically purified C42D FdI is a seven-iron, protein retaining its [4Fe-4S](2+/+) cluster with monodentate aspartate, ligation to one iron. Unlike known clusters of this type the reduced, [4Fe-4S](+) cluster of C42D FdI exhibits only an S = 1/2 EPR with no, higher spin signals detected. The cluster shows only a minor change in, reduction potential relative to the native protein. All attempts to, convert the cluster to a 3Fe cluster using conventional methods of oxygen, or ferricyanide oxidation or thiol exchange were not successful. The, cluster conversion was ultimately accomplished using a new electrochemical, method. Hydrophobic and electrostatic interaction and the lack of Gly, residues adjacent to the Asp ligand explain the remarkable stability of, this cluster.
About this StructureAbout this Structure
1FF2 is a Single protein structure of sequence from Azotobacter vinelandii with SF4 and F3S as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Structure of C42D Azotobacter vinelandii FdI. A Cys-X-X-Asp-X-X-Cys motif ligates an air-stable [4Fe-4S]2+/+ cluster., Jung YS, Bonagura CA, Tilley GJ, Gao-Sheridan HS, Armstrong FA, Stout CD, Burgess BK, J Biol Chem. 2000 Nov 24;275(47):36974-83. PMID:10961993
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