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  • Title: Mössbauer study of the inactive Fe3S4 and Fe3Se4 and the active Fe4Se4 forms of beef heart aconitase.
    Author: Surerus KK, Kennedy MC, Beinert H, Münck E.
    Journal: Proc Natl Acad Sci U S A; 1989 Dec; 86(24):9846-50. PubMed ID: 2557631.
    Abstract:
    Active beef heart aconitase contains an iron-sulfur cluster with an [Fe4S4]2+ core. This cluster can be converted into Fe3S4 with concomitant loss of enzymatic activity. We have reconstituted apo-aconitase with iron and selenide to obtain Fe4Se4 aconitase. The Se analog has higher catalytic activity than the native S-containing enzyme when isocitrate is the substrate. Oxidation of [Fe4Se4]2+ with ferricyanide yields the inactive [Fe3Se4]1+ form. The Se-containing 3-Fe cluster can be reduced to [Fe3Se4]0. We have studied the [Fe3S4]1+,0, [Fe3Se4]1+,0, and [Fe4Se4]2+ states with Mössbauer spectroscopy from 1.3 K to 200 K in magnetic fields up to 6.0 T. The spectra of the S- and Se-containing enzymes were found to be remarkably similar. The spectra of the 3-Fe clusters were analyzed and the salient features of the electronic structure are discussed.
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