MitoNEET is a small mitochondrial protein that has been identified recently as a target for the thiazolidinedione (TZD) class of diabetes drugs. MitoNEET also binds a unique three-Cys- and one-His-ligated [corrected] [2Fe-2S] cluster. Here we use protein film voltammetry (PFV) as a means to probe the redox properties of mitoNEET and demonstrate the direct impact of TZD drug binding upon the redox chemistry of the FeS cluster. When TZDs bind, the midpoint potential at pH 7 is lowered by more than 100 mV, shifting from approximately 0 to -100 mV. In contrast, a His87Cys mutant negates the ability of TZDs to affect the midpoint potential, suggesting a model of drug binding in which His87 is critical to communication with the FeS center of mitoNEET.
