The Road Less Traveled:

For Love of Detection, Discovery, and All Things Radical

Abstract: RNRs catalyze the conversion of nucleotides to deoxynucleotides (ND(T)Ps to dND(T)Ps) providing the monomeric precursors required for DNA replication and repair in all organisms. In all three classes of RNRs a subunit a houses a conserved 10 stranded α/β barrel with a finger loop in its center that initiates catalysis using a cysteinyl radical. This radical in all RNRs is generated by diverse metallocofactors. In class Ia enzymes, they are located in a second subunit β. In the human and Ec RNRs, a tyrosyl radical in β reversibly generates the thiyl radical in α by a radical transfer pathway that occurs over 32 Å and involves 5 or 6 amino acid radical intermediates. The control of this unprecedented reaction and the ability of these enzymes to prevent their own demise is rather remarkable. I will focus on what the collective we have learned about these enzymes using methods including site-specifically incorporated unnatural amino acids, rapid kinetics, multi-frequency EPR, cryo-EM, and photo-RNRs. Mechanism-based inhibitors have played an important role including potentially new ways to look at the enzyme structures and to potentially generate clinically useful therapeutics. I have been lucky to have been able to pursue my passions with so many outstanding collaborators over the past decades. I also have been SO lucky to interact with and teach/learn from so many students.