Interconversion between [2Fe–2S] and [4Fe–4S] cluster glutathione complexes

Abstract

We present here how different iron–sulfide–glutathione ratios, applied in in vitro conditions comparable to those present in the mitochondrial matrix, affect the speciation of iron–sulfur cluster glutathione complexes. An excess of sulfide with respect to iron ions promotes the formation of a tetranuclear [Fe^II₂Fe^III₂S₄(GS)₄]²⁻ complex, while an excess of iron ions favors the formation of a dinuclear [Fe^IIFe^IIIS₂(GS)₄]³⁻ complex. These two complexes establish an interconversion equilibrium. The latter might play a role in the composition of the mitochondrial labile iron pool potentially contributing to the regulation of cellular iron homeostasis.