Lance C. Seefeldt
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B.S., 1983, University of Redlands, California
Ph.D., 1989, University of California, Riverside
Postdoctoral, 1989-93, University of Georgia
Our laboratory is using multidisciplinary approaches including molecular biology, biochemistry, and biophysics to elucidate a molecular understanding of the mechanism of the metalloenzyme nitrogenase.
Nitrogenase is the enzyme responsible for all biological nitrogen fixation, a central reaction in the global nitrogen cycle. The reduction of N2 to NH3 catalyzed by nitrogenase can be summarized by the
N2 + 8 H+ + 8 e- +16 MgATP —> 2 NH3 + H2 + 16 MgADP + 16 Pi
Biological nitrogen fixation accounts for approximately 80 % of the total input of fixed nitrogen into the biosphere each year (in excess of 2 x 10^14 grams/year) and thus is essential to all living systems.
Given the significance of the reaction catalyzed by nitrogenase, there is considerable interest in understanding how the enzyme works. Nitrogenase is a complex metalloproteins that contains three different metal-based centers.
We are working towards providing answers to four outstanding questions regarding how nitrogenase works: 1) How does N2 bind to the nitrogenase active site, 2) How are electrons delivered to the active site for N2 reduction, 3) What are the roles for MgATP hydrolysis in the reaction, and 4) How are the unusual metal centers of nitrogenase biosynthesized. To gain answers to these questions, we are employing a range of approaches including site-directed mutagenesis, EPR, rapid kinetics, NMR, CD, and x-ray spectroscopy. Students working in the group gain first hand training in these and other methods that are ideal for pursuing jobs in industry or academics.
Selected Recent Publications (total of 150)
Yang, Z.-Y., Ledbetter, R., Shaw, S., Pence, N., Tokmina-Lukaszewska, M., Eilers, B., Guo, Q., Pokhrel, N., Cash, V. L., Dean, D. R., Antony, E., Bothner, B., Peters, J. W., and Seefeldt, L. C. (2016) Evidence That the Pi Release Event Is the Rate-Limiting Step in the Nitrogenase Catalytic Cycle. Biochemistry.
Milton, R. D., Abdellaoui, S., Khadka, N., Dean, D. R., Leech, D., Seefeldt, L. C., and Minteer, S. D. (2016) Nitrogenase bioelectrocatalysis: heterogeneous ammonia and hydrogen production by MoFe protein. Energy Environ. Sci.
Lukoyanov, D., Khadka, N., Yang, Z.-Y., Dean, D. R., Seefeldt, L. C., and Hoffman, B. M. (2016) Reversible Photoinduced Reductive Elimination of H2 from the Nitrogenase Dihydride State, the E4(4H) Janus Intermediate. J. Am. Chem. Soc. 138, 1320–1327.
Brown, K. A., Harris, D. F., Wilker, M. B., Rasmussen, A., Khadka, N., Hamby, H., Keable, S., Dukovic, G., Peters, J. W., Seefeldt, L. C., and King, P. W. (2016) Light-driven dinitrogen reduction catalyzed by a CdS:nitrogenase MoFe protein biohybrid. Science 352, 448–450.
Lukoyanov, D., Yang, Z.-Y., Khadka, N., Dean, D. R., Seefeldt, L. C., and Hoffman, B. M. (2015) Identification of a Key Catalytic Intermediate Demonstrates That Nitrogenase Is Activated by the Reversible Exchange of N2 for H2. J. Am. Chem. Soc. 137, 3610–3615.