Degree

Doctor of Philosophy (PhD)

Department

Biological Sciences

Document Type

Dissertation

Abstract

Mitochondrial NEET proteins are recently discovered iron-sulfur proteins that are localized within mitochondria. There are three NEET proteins: mitoNEET, a type II diabetes drug pioglitazone binding target, a mitoNEET related protein 1 (Miner1 or NAF-1), and a mitoNEET-related protein 2 (Miner2). While both mitoNEET and Miner1 are mitochondrial outer membrane proteins, Miner2 is a mitochondrial matrix protein. All three NEET proteins bind at least one [2Fe-2S] cluster via CDGSH (Cys-Asp-Gly-Ser-His) motif. In this work, we have investigated the electron transfer activity of mitoNEET, and found that the CDGSH-type [2Fe-2S] clusters of mitoNEET can be reduced by the reduced flavin mononucleotide (FMNH2) under anaerobic or aerobic conditions in vitro. We have also found that the reduced mitoNEET [2Fe-2S] clusters can be oxidized by ubiquinone or oxygen. Further studies have demonstrated that the type II diabetes medication pioglitazone may compete for the FMNH2 binding site of mitoNEET, and inhibit the reduction of the mitoNEET [2Fe-2S] clusters by FMNH2. We have also described the inhibitory effect of nitric oxide on the electron transfer activity of the mitochondrial matric protein Miner2. We have found that nitric oxide can bind to the reduced Miner2 [2Fe-2S] clusters without disruption of the cluster, and that visible light excitation can quickly release nitric oxide from the nitric oxide-bound cluster in Miner2. Binding of nitric oxide effectively inhibits the electron transfer activity of the Miner2 [2Fe-2S] clusters. The results suggest that mitochondrial NEET-proteins may play a novel role in energy metabolism in cells, and that nitric oxide may regulate the electron transfer activity of the NEET-proteins and modulate the energy metabolism in mitochondria via directly binding to the [2Fe-2S] clusters in the proteins.

Committee Chair

Huangen Ding

Included in

Biochemistry Commons

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