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Project Progress

Although wide spread among anaerobic procaryotes, a physiological function for a recently described flavoprotein family (iron-sulfur flavoprotein (Isf)) was unknown. We determined that Isf from the methane-producing archaeon Methanosarcina thermophila is able to reduce O₂ and H₂O₂ to water, thereby detoxifying these reactive oxygen species and protecting the organism from oxidative stress. We also showed that tryptophan repressor binding protein (WrbA), previously hypothesized to be a regulatory protein, is a quinone reductase which reduces quinones to the fully-reduced state avoiding the semiquinone that interacts with O₂ to produce toxic superoxide radicals. Thus, the function of two new families of proteins have been determined to be involved in the oxidative stress response of anaerobic procaryotes from the Bacteria and Archaea domains. A further understanding of the ancient gamma-class carbonic anhydrase was accomplished that sheds light on the evolution of this class and how it functions in the methane-producing Archaea. Finally, together with Christopher House, we developed a novel theory for early evolution of the cell. In contrast to current paradigms, we proposed that an energy-conservation pathway was the major force which powered and directed early evolution. We further proposed that energy conservation played the predominant role in the later evolution of anaerobic metabolisms which explains the origin and evolution of extant methanogenic pathways.