In this award from the Chemistry of Life Processes Program in the Chemistry Division, Dr. Gary Gerfen, from the Albert Einstein College of Medicine of Yeshiva University, will investigate the mechanism of turnover by and inhibition of the enzyme ribonucleoside triphosphate reductase. Ribonucleotide reductases (RNRs) are present in all cellular non-parasitic organisms characterized to date, and are also encoded by many DNA viruses. These enzymes catalyze the reduction of nucleotides to the corresponding deoxyribonucleotides, the only known means of de novo generation of precursors for both DNA replication and repair. Despite significant progress being made in the study of all classes of RNR recently, questions remain regarding mechanisms of substrate turnover, inactivation by mechanistic inhibitors and allosteric regulation. The objective of this award is to focus on the simplest representative RNR, ribonucleoside triphosphate reductase (RTPR) from Lactobacillus leichmannii. Gaining insight into the reaction mechanism and allosteric regulation of this simplest of the ribonucleotide reductases will contribute to basic understanding of this important class of enzymes. Dr. Gerfen will investigate the mechanism of substrate turnover using ribonucleotides and active site mutants, and the mechanism of inhibition and inactivation using mechanism-based inhibitors. Finally, the structure and dynamics of regions of RTPR thought to be important for allosteric regulation will be probed using room temperature continuous wave and low temperature pulsed site directed spin label electron paramagnetic resonance techniques.
Ribonucleotide reductases are enzymes that provide the only known way to make the building blocks of DNA in almost all organisms. Because DNA is crucial to every aspect of cellular function, these enzymes play an essential role in the metabolism of organisms from bacteria to humans. Defects in the structure and function of these enzymes lead to many diseases, and antibacterial and anticancer drugs designed to inhibit the function ribonucleotide reductases are currently in clinical use. However, it is not understood how the drugs that inactivate these enzymes function. Dr. Gerfen's work will give us better understanding of the basic mechanisms by which ribonucleotide reductases function.
