NifI Proteins of Methanococcus Maripaludis

University Of Washington, Seattle WA

Investigators

Abstract

A grant has been awarded to Dr. John Leigh at the University of Washington to study proteins involved in a novel mechanism of nitrogen regulation that occurs in certain methanogenic Archaea. Methanogenic Archaea are a group of microorganisms that produce methane as a metabolic product. In addition, some species of methanogenic Archaea can fix nitrogen, that is, convert atmospheric nitrogen to valuable ammonia nitrogen. The process of nitrogen fixation is rigorously regulated by microorganisms, because only when an organism is nitrogen-starved is it advantageous to obtain needed nitrogen via nitrogen fixation. The control of the activity of the enzyme that catalyses nitrogen fixation, nitrogenase, is one way in which the regulation occurs. Regulation of nitrogenase activity will be studied in Methanococcus maripaludis, a species that serves as a particularly good laboratory model. The focus will be on proteins called NifI1 and NifI2, which are hypothesized to sense the degree of nitrogen starvation and to interact with other proteins to effect regulation. The project will investigate the role of metabolic intermediates as indicators of nitrogen starvation, the interaction of those intermediates with NifI1 and NifI2, the modifications of NifI1 and NifI2 that might occur, and the interaction of NifI1 and NifI2 with other proteins that might be involved in the regulation of nitrogen fixation. The research will provide important training to graduate students, undergraduate students, and postdoctoral trainees, who will participate in the research activities. The research will also contribute to the resources available to the scientific community through the continued development of Methanococcus maripaludis as a model species for studies in the Archaea. The results will bear directly on teaching students the principles of regulation and of nitrogen assimilation by organisms. The regulation of nitrogen fixation has broad significance to human agriculture. Biological nitrogen fixation has huge environmental and nutritional importance because it is the primary means of cycling nitrogen from the atmosphere to the biosphere. The work should lead to fundamental new insights into the regulation of this process in a major group of organisms.