2015 Hellman Fellow
Assistant Professor, Molecular Biology and Biochemistry
Project Title: Engineering Chimeric Proteins for Biofuel Production
Project Summary: Methanogenesis, photosynthesis and nitrogen fixation are three metabolic processes central to the emergence and evolution of life on Earth. The significance of these processes can be appreciated from the perspective of their positive impact on environment, agriculture and energy. Wither regard to environment, both methanogenic and photosynthetic microorganisms assimilate carbon dioxide (CO2) for cell growth, thereby reducing the emission of this greenhouse gas in atmosphere. With regard to agriculture, nitrogen-fixing microorganisms reduce nitrogen (N2) to ammonia (NH4+), a usable form of nitrogen that is essential for all forms of life on Earth. Perhaps more excitingly, nitrogenase, the enzyme responsible for the reduction of N2 to NH4+, was also shown to reduce carbon monoxide (CO) and CO2 to hydrocarbons, thereby ‘recycling’ the carbon in these harmful gases into the useful carbon fuels. In addition, hydrogen (H2), a clean energy source, is generated as an abundant side product in the reactions of N2-, CO- and CO2-reduction by nitrogenase.
Interestingly, despite their differences in the time and ecological scales of evolution, it has been suggested that methanogenesis, photosynthesis and nitrogen fixation are three related processes. The identification of a set of homologous proteins shared by these processes (designated Nfl, Bch and Nif, respectively) provides strong support to this theory; in particular, a striking structural-functional parallelism has been proposed or establishedfor NflD (methanogenesis), BchNB (photosynthesis) and NifDK (nitrogen fixation), which are structurally homologous proteins carrying different cofactors or prosthetic groups (i.e., NifD/F430; BchNB/Chl; and NifDK/M cluster) at analogous binding sites. The homology between these proteins not only implies an interesting co-evolution of these seemingly unrelated processes, but also suggests a distinct possibility to couple these metabolic features into useful functions. Based on this hypothesis, the overarching goal of my research is to identify natural hosts and engineer hybrid systems that couple biofuel (i.e., hydrocarbon) production with the consumption of factory exhaust (i.e., CO) and greenhouse gas (i.e., CO2), which will contribute to the reduction of greenhouse gas emissions while improving the environmental performance of biofuel production.
Faculty webpage: http://www.faculty.uci.edu/profile.cfm?faculty_id=6020