Competition of zinc ion for the [2Fe-2S] cluster binding site in the diabetes drug target protein mitoNEET.

Human mitochondrial protein mitoNEET is a novel target of type II diabetes drug pioglitazone, and contains a redox active [2Fe-2S] cluster that is hosted by a unique ligand arrangement of three cysteine and one histidine residues. Here we report that zinc ion can compete for the [2Fe-2S] cluster binding site in human mitoNEET and potentially modulate the physiological function of mitoNEET. When recombinant mitoNEET is expressed in Escherichia coli cells grown in M9 minimal media, purified mitoNEET contains very little or no iron-sulfur clusters. Addition of exogenous iron or zinc ion in the media produces mitoNEET bound with a [2Fe-2S] cluster or zinc, respectively. Mutations of the amino acid residues that hosting the [2Fe-2S] cluster in mitoNEET diminish the zinc binding activity, indicating that zinc ion and the [2Fe-2S] cluster may share the same binding site in mitoNEET. Finally, excess zinc ion effectively inhibits the [2Fe-2S] cluster assembly in mitoNEET in E. coli cells, suggesting that zinc ion may impede the function of mitoNEET by blocking the [2Fe-2S] cluster assembly in the protein.