This proposal is for a study to compare the mechanism of action of mammalian ribonucleotide reductase with its bacterial counterpart. The subunits of the enzyme will be produced using plasmids available in the laboratory where Dr. Hicks will be spending a sabbatical year. This will be one of the first opportunities to obtain an abundant amount of the mammalian enzyme and compare its properties to the bacterial one. The tyrosyl radical-dinuclear iron cluster of the mammalian enzyme will be studied by stopped-flow absorption spectroscopy. Studies of the mechanism of action of this enzyme will be done using substrate analogs and mechanism-based inhibitors. The mammalian enzyme has been reported to be much less stable than the bacterial one; this study should give new information about dinuclear non-heme iron clusters in this type of enzyme. %%% The components of DNA, the genetic material, are produced by a protein called ribonucleotide reductase. This protein contains iron atoms which are non-covalently linked to the amino acid tyrosine. Most iron in proteins is present as part of hemoproteins such as hemoglobin, in blood, or myoglobin, in muscle. Ribonucleotide reductase does not have this type of iron-protein linkage. The investigator plans to compare the properties of the protein isolated from mouse with the much more well-characterized protein from a bacterium. She will use several biophysical techniques to determine this.
