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Dennis Winge

Professor of Medicine and of Biochemistry

B.A. Concordia College

Ph.D. Duke University

Research

References

dennis.winge@hsc.utah.edu

Dennis Winge's Lab Page

Research

One area of active research is the assembly of cytochrome oxidase (CcO) in mitochondria. This enzyme complex (13 subunits) is the terminal oxidase in respiration. Its structure is shown below. Assembly of CcO requires the coordinate expression and binding of subunits synthesized on both cytoplasmic and mitochondrial ribosomes. In addition, the enzyme requires a number of cofactors for function. The assembly process is known to require more than 30 proteins. Mutations in a number of the human assembly orthologs result in cardiomyopathies. We are working on the process of cofactor insertion to the mitochondrially encoded subunits. At least seven proteins are important for assembly of the copper centers of CcO and an additional series of proteins are important for synthesis and insertion of the heme A cofactors. The assembly factors are conserved from yeast to man, so our assembly studies in yeast provide a working model for the process in humans. We use a combination of in vitro biochemical and in vivo cellular assays to elucidate the mechanism and pathway by which these proteins insert cofactors. A number of the key proteins that function in the insertion of subunits in the inner membrane interact with key cofactor insertion molecules, suggesting that cofactor insertion is a co-translational process. Copper ion metallation of CcO occurs within the mitochondrial intermembrane space (IMS), yet the copper ions appear to be derived from the mitochondrial matrix. The matrix copper fraction is a novel copper complex conserved from yeast to the mouse. We are using biophysical techniques to structurally characterize the matrix copper complex and genetic approaches to identify the key transporters that transport copper ions from the matrix to the IMS for Cox17 mediated delivery of copper ions to the insertion complex.

We discovered that mitochondria also contain a labile, storage pool of zinc that is utilized in metallation of key zinc metalloenzymes within the mitochondrion. We are attempting to identify the labile zinc complex and the transporters that maintain this important matrix zinc pool.

Third, we are working on a series of metal ion sensory proteins that function in metal-dependent signal transduction and cellular metal homeostasis in yeast. We work on the structure and function of five copper-, iron-, and zinc-specific metalloregulatory proteins in yeast. These metal regulatory proteins are transcription factors that are either activated or repressed by specific metal ions. Metal-induced conformational dynamics are important in regulating the function of these transcription factors.  The transcriptional activators Aft1 and Aft2 are iron-regulatory factors that function in maintaining iron homeostasis in yeast. These factors are specifically activated in iron-deficient cells and induces the expression of >20 genes. Both factors are inhibited in iron-replete cells from a signal deriving from the mitochondrion involving iron-sulfur cluster biogenesis. We are working to elucidate the nature of the iron-inhibitory signal from the mitochondrion that regulates Aft1 activity. This signaling pathway involves two glutaredoxins, yet it isn’t clear how these glutaredoxins mediate iron-inhibition of Aft1.

 

References