SGER: Novel Nitrogenase-like Proteins and the Evolution of the Nitrogen Cycle

Arizona State University, Scottsdale AZ

Investigators

Abstract

This SGER project is concerned with the characterization of a putative new class of enzymes evolutionarily related to nitrogenase. These proteins have been discovered using genomic methods in a number of organisms, including several that are not diazotrophic. The proteins are evolutionarily related to nitrogenase but almost certainly catalyze other, as yet unknown, chemical reactions. These proteins may be the direct descendents of the primitive ancestors of nitrogenase, because of their basal position in the phylogenetic tree and the single type of subunit in the reductase portion of the complex. In this project, genes for these nitrogenase-like proteins (NflH and NflD) will be cloned from Methanococcus jannaschii and will be expressed in E. coli. Using antibodies obtained from these recombinant proteins, native forms of these same proteins from M. jannaschii will be purified and characterized. It is possible that a unique activity will be determined for these proteins, which could imply a role for a pre-nitrogenase homolog on the early Earth. A further understanding of the mechanism of nitrogenase might also be realized, if a similar substrate or activity is found in these homologs. Broader Impacts: This project will enhance our understanding of the origin and evolution of the nitrogen cycle, which will give important insights into the early evolution of life and the origin of metabolism. This project will involve training of a postdoctoral fellow and will contribute to the development of a scientifically trained workforce.