Research Interests   Protein Structure; Metalloproteins

The primary and three-dimensional structure of a protein substantially determines the function of metallocenters in biological electron transfer reactions. The primary goal of my group is to understand how protein interactions influence the properties of Fe:S clusters in the nitrogen fixation complex and in thermostable proteins.

Nitrogen fixation is the only biological process for providing ammonia to the biosphere. Understanding the process has important ecological and economic consequences. Our research in nitrogen fixation can provide the foundation for developing efficient non-biological catalysts as well as more efficient microbial nitrogen fixation.

The nitrogenase components are metalloproteins whose primary sequences were determined in my laboratory. The recent three-dimensional structures of these proteins make possible rational structure-mechanistic correlations. From chemical modification and site-specific mutagenesis studies, we have determined the probable protein-protein "docking" sites. Of immediate interest for us is how ATP hydrolysis is coupled to electron transfer, how the electrons are directed to the substrate and how the various metallocenters are synthesized and inserted.

A second interest of our group is the study of thermostable enzymes with iron-sulfer clusters. The main question we are considering is how these proteins composed of the standard amino acids are able to maintain their structure and function at greater than 100 o C.

Rees, D.C., Schindelin, H., Kisker C., Schlessman, J.W., Peters, J.W., Seefeldt, L.C. and Howard, J.B. (1998) "Complex Structures of Nitrogenase." Current Plant Science and Biotechnology Agriculture 31.

Renner, K. A., and Howard, J.B. (1996) "Aluminum Fluoride Inhibition of Nitrogenase: Stabilization of a Nucleotide-Fe-Protein-MoFe-Protein Complex." Biochemistry 35: 5353.

Howard, J. B. and Rees, D. C. (1996) "Structural Basis of Biological Nitrogen Fixation" Chem. Rev.

Teng, Q., Zhou, Z., Smith E., Busse, S., Howard, J. B., Adams, M., and LaMar, G., (1994) "Solution 1H NMR Determination of the Secondary Structure for Three-Iron Form of the Ferredoxin from the Hyperthermophilic Archaeon Pyrococcus furosia" Biochemistry 33: 6316-6326.

Wolle, D., Dean, D., and Howard, J. B., (1992) "Nucleotide-Fe:S Cluster Signal Transduction in the Nitrogenase Fe-Protein: The Role of Aspartic Acid 125", Science 258: 992.

Howard, J. B., and Rees, D., (1994) "Nitrogenase: A Nucleotide-Dependent Molecular Switch" Ann. Rev. Biochemistry, 63: 235-264.