The research proposed herein seeks to determine the structural organization and function of the MoFe protein of Azotobacter vinelandii nitrogenase and how the protein is organized to deliver the required reducing equivalents to substrate. The project seeks funding for biochemical and biophysical experiments on an entity called the FeMo- cluster which may represent the inorganic portion of the FeMo-co site, on a form of the MoFe protein which only contains the [4Fe-4S]-type clusters, on the interaction of the Fe protein/MgATP complex with that protein and on the process of inserting FeMo-co into the protein. These experiments are designed to determine the chemical, redox and physical properties of each component of the MoFe holoprotein and how they interact with each other and other components of the nitrogenase system. This research project will determine the individual responsibilities of the various portions of the MoFe for catalysis and will thus delineate the internal molecular workings of the MoFe protein. Such information will be invaluable in attempts to enhance biological nitrogen fixation or to duplicate it synthetically for agronomic benefit. Increased fixed nitrogen ability equates to increased protein supply, which is a significant factor in good nutrition and health.