Oxidative disassembly of the [2Fe-2S] cluster of human Grx2 and redox regulation in the mitochondria.

Mitochondrial Grx2 is a new member of the thioredoxin superfamily that has been found to bind a [2Fe-2S] cluster in a novel coordination motif at the interface of a homodimer, where cluster binding occurs via a catalytic cysteine residue and a molecule of GSH (per monomer). The (Grx2)(2)-[2Fe-2S] dimer is thought to undergo cluster destruction and monomerization in a redox-induced pathway of activation. In this report, we make use of protein film voltammetry (PFV) as a method to probe the stability of the Grx2-[2Fe-2S] cluster, using oxidative poises of varying potential and duration to probe the thermodynamic and kinetic stability of the cluster's electrochemical response. We find that the cluster signal is stable at positive potentials up to 0.5 V but that cluster destruction occurs readily when oxidative pulses in excess of this value are applied.