With this award, the Chemistry of Life Processes Program is funding Dr. Evert Duin of Auburn University and Dr. John Leigh of the University of Washington to study the important process of electron bifurcation, which occurs when living systems convert energy from one form to another. In this process, two electrons enter the system with identical potential, but when they exit, one has a much lower potential than the other. Consequently, electron bifurcation makes possible an uphill, energy-demanding, electron reduction of a biological molecule because a downhill oxidation occurs concomitantly, which balances the energy consumption and generation. The process has been observed in the methane-producing and -consuming functions of Archaea, which produce biofuels, but also in other forms of life, including our own bodies. Understanding how this process works could be beneficial for improving the production of biogas or helping to optimize the conversion of methane to biodiesel and could help us answer a variety of health-related questions. The research has a further broader impact on the preparation of students at all educational levels to become the next generation of scientists. The collaborative nature of the project that involves groups from different geographic regions of the United States creates an environment in which the students acquire skills for interdisciplinary and collaborative research.
Electron bifurcation enables enzymes to create electrons with a very low redox potential by simultaneously creating an electron with a high redox potential. This eliminates the need to couple the former electron transfer step to ATP hydrolysis. The bifurcation process always involves a quinone or flavin group. The Duin and Leigh groups will study the electron bifurcation by the hydrogenase:heterodisulfide reductase complex, which contains iron ions within iron-sulfur clusters. The theory is that some of the iron-sulfur clusters play an important part in the electron bifurcation process by donating electrons to the central flavin and then accepting either the high or low potential electrons. Site-direct mutagenesis will be used to make changes to the iron-sulfur clusters and to the flavins and their direct environment. The consequences of these changes on the electronic and magnetic properties of the clusters and flavins will be evaluated by absorption, electron paramagnetic resonance, and magnetic circular dichroism spectroscopies and the bifurcation process will be examined by determining the redox properties of the clusters and flavins and the kinetics of the redox processes.