Iron-sulfur cluster interconversions

The mimicking of the iron-sulfur clusters by synthetic chemistry has been quite successful over the years. One of the last synthetic clusters to be obtained was the [3Fe-4S] cluster (109, 110). This new synthetic compound was useful for the demonstration of interconversion pathways, as well as for the formation of different heterometal clusters beyond those produced in proteins (111). The [3Fe-4S] core... 

In particular, the study of SRB ferredoxins enables us to survey the different properties of simple iron-sulfur proteins, including electron transfer, flexibility in coordination chemistry, and ability to undergo cluster interconversions. Most of the observations can be extrapolated to more complex situations. 

An abbreviation for Ifigh-potential iron-sulfur protein, which is now regarded as a ferredoxin. In its role as a bacterial electron transfer component, this [4Fe-4S] cluster protein can undergo interconversion to the [4Fe-4S] and [4Fe-4S] states. 

This account will deal in turn with structural features of the one-iron, two-iron, four-iron and three-iron proteins, and also with the most important topic of interconversion between the three-iron and four-iron clusters. Model compounds will be described briefly. Finally, kinetic studies and the role of iron-sulfur proteins in complex enzymes will be discussed. 

The [3Fe-4S] core present in D.gigas Fd II can be interconverted into a cubane structure [4Fe-4S]. This fadie conversion occur upon incubation of the protein with an excess of Fe in the presence of a reducing agent (e.g. dithiothreitol). A summary of the interconversion pathways as well as the potentialities of the method for specific labelling an iron-sulfur core was previously discussed (26,49). Combination of Fe isotopic enrichment and specific introduction of a forth iron atom into the [3Fe-4S] core produces different isotopic labelled clusters. 

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