This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
Intellectual Merit The iron-molybdenum cofactor (FeMo-co, 7Fe-9S-Mo-X-homocitrate), found within the active site of the enzyme nitrogenase, is among nature's most complex hetero-metallic cofactors and is required to catalyze the chemically difficult reduction of dinitrogen (N2) to ammonia (NH3). FeMo-co is synthesized by a multi-step pathway with the involvement of multiple different proteins that couple Fe, S and Mo. Currently, the exact structures of the pathway intermediate Fe-S clusters are unknown and even less is known regarding the molecular mechanisms of the enzymes such as NifB and NifEN that catalyze the bio-metallic reactions. By combined genetic, biochemical and spectroscopic techniques, this research aims to determine the exact structures of the pathway intermediates and uncover the enzymatic mechanisms that perform the multi-step bio-metallic reactions that are the foundation of biological nitrogen fixation. The major focus will be placed on NifB and its product, NifB-co, that form the early part of the FeMo-co biosynthetic pathway. The NifB enzyme, NifB-co, as well as isotopic analogs, will be examined by EPR, Mössbauer, EXAFS and NRVS spectroscopic techniques. These spectroscopic inspections will be complemented by biochemical analysis to determine the exact step(s) and mode of incorporation of each Fe, S and the interstitial atom X.
Broader Impact All life depends on the input of the element nitrogen into the biosphere by biological nitrogen fixation catalyzed by FeMo-co. Understanding how the enzymes of the FeMo-co biosynthesis pathway perform the bio-metallic chemistry may lead to design and synthesis of novel catalysts to improve Haber-Bosch processes for fertilizer production resulting in a decrease in energy costs for agriculture. Both graduate and undergraduate students will have a major role in this research and will be trained in a wide range of cross-disciplinary techniques. As a part of this project, an outreach activity that targets junior and senior High School students will be performed. The designed activity will bring biochemistry into the secondary education classroom.
