Structure of Mitochondrial Complex I Determined

Mitochondria produce ATP, the energy currency of the body. The driver for this process is an electrochemical membrane potential, which is created by a series of proton pumps. These complex, macromolecular machines are collectively known as the respiratory chain. The structure of the largest protein complex in the respiratory chain, that of mitochondrial complex I, has now been elucidated by scientists from the Frankfurt "Macromolecular Complexes" cluster of excellence, working together with the scientists at University of Freiburg, by X-ray diffraction analysis. The results were published in the January 2, 2015 issue of Science. "Mitochondrial complex I plays a critical role in the production of cellular energy and has also been associated with the onset of diseases, such as Parkinson's disease," explains Dr. Volker Zickermann, an Assistant Professor at the Institute for Biochemistry II at the Goethe University in Frankfurt am Main, Germany. In order for the respiratory chain to function, there must be consistently sufficient amounts of oxygen available in all the cells in our bodies. The energy released during biological oxidation is used to transport protons from one side of the inner mitochondrial membrane to the other. The resulting proton gradient is the actual "battery" for ATP synthesis. What surprised the researchers was that previous studies had suggested that redox reactions and proton transport in complex I occurred spatially isolated from one another. The Frankfurt scientists in Dr. Zickermann's working group at Goethe University, and the working groups led by Professor Harald Schwalbe and Professor Ulrich Brandt, both also at Goethe University, have now been able to deduce how the two processes are connected to one another from the detailed analysis of the structure.
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