ISSN:
1432-1327
Keywords:
Key words Ferricyanide
;
Oxidation
;
[Fe-S] clusters
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract Crystals of Azotobacter vinelandii ferredoxin I (FdI) have been soaked in solutions containing K3Fe(CN)6 in order to study the oxidation of the [3Fe-4S] and [4Fe-4S] clusters in the protein. Ferricyanide treatment results in partial loss of Fe and S from each cluster accompanied by alteration of Fe-S bonds. The effects of oxidation can be quantitated by crystallographic refinement when each [Fe-S] cluster is modeled as having a single, average structure with non-standard geometry. The oxidized clusters refined at 2.1-Å resolution display statistically significant deviations from geometric ideality. If interpreted in terms of atomic shifts these deviations indicate that each cluster first loses an inorganic S atom. In each case an Fe atom bonded to this S separates from the remaining atoms of the cluster such that the [3Fe-4S] and [4Fe-4S] clusters partially decompose into a single Fe plus 2Fe and 3Fe fragments. The extent of structural changes observed are essentially the same in crystals soaked at 3 : 1, 9 : 1 and 30 : 1 mole ratio of K3 Fe(CN)6 : FdI, suggesting that the crystal lattice permits limited oxidation reactions to occur at a low mole ratio but restricts conformational changes from occurring that may be required for more extensive oxidative reactions at higher mole ratio. The results are relevant to understanding the transformations which may take place when [Fe-S] proteins are deliberately oxidized with ferricyanide.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/PL00010650
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