Physical Interactions of the Mitochondrial Electron Transfer Chain and Fatty Acid Oxidation

Yudong Wang1, Johan Palmfeldt2, Neils Gregersen2, Alexander Makhov3, J Conway3, Steve McCalley1, Meicheng Wang4, Hana Alharbi1, Shrabani Basu1, Xuemei Zeng6, Nathan Yates5, and Jerry Vockley1,6

1Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, PA

2 Research Unit for Molecular Medicine, Aarhus University Hospital, Aarhus, Denmark

3 Department of Structural Biology, University of Pittsburgh, Pittsburgh, PA

4 Department of Pharmacology, University of Pittsburgh School of Pharmacy,
Pittsburgh, PA

5 Department of Cell Biology, University of Pittsburgh School of Medicine,
Pittsburgh, PA

6 Department of Human Genetics, Graduate School of Public Health,
University of Pittsburgh, Pittsburgh, PA

Efficient cellular function demands coordination of oxidative phosphorylation (OXPHOS), fatty acid oxidation (FAO), and the tricarboxylic acid (TCA) cycle. OXPHOS is organized into higher order structures called super complexes. We have previously shown that proteins of FAO and OXPHOS physically and functionally interact in mitochondria. We report use of blue native-2D western blots, proteomic techniques, immune-electron microscopy, and stimulated emission depletion (STED) microscopy studies to characterize specific sites of interaction of FAO proteins with each other and OXPHOS super complexes.

The mitochondrial trifunctional protein, an NADH generating enzyme, directly interacts with the complex I matrix NADH binding domain, as well as with very long chain acyl-CoA dehydrogenase of fatty acid oxidation. Electron transfer flavoprotein dehydrogenase, which funnels reducing equivalents from acyl-CoA dehydrogenases in fatty acid oxidation to OXPHOS chain complex III, was found to interact with core proteins of complex III, which are also linked with complex I. These findings are consistent with the functional interaction of the two enzymes in super complexes.

Our results provide growing insight into the molecular architecture of mitochondrial energy metabolism. The likely impact on disease will be discussed.