The Fe2-Y• cofactor is indispensable to RNR activity. The interruption of the cofactor assembly and repair is a potential route for drug development. The cofactor assembly requires Fe2+ binding, O2 activation, and an external reductant. The cofactor repair requires the reduction of the inactive Fe2(III) form to its Fe2(II) state, to re-enter the biosynthesis pathway. We aim to identify the accessory proteins required in the delivery of Fe2+ and e– in these processes in vitro and in vivo.
Class Ia RNRs studied so far adopt a variety of α/β complexes. In E. coli RNR, the active form is α2β2 and the dATP inhibited form is an α4β4 complex, whereas the inhibited form of human RNR is α6. It remains unclear what is the active form of human RNR. The challenge is that the active complex only forms transiently and is therefore difficult to isolate and characterize. We will employ unnatural amino acids to stabilize the radical intermediates and characterize them using a variety of biophysical methods.
It is of great interest to discover RNR inhibitors for therapeutic purposes: the inhibitors of human RNRs are potentially anti-cancer agents whereas the inhibitors of RNRs from pathogenic bacteria and viruses can be candidates for antibiotics and antivirals. An ideal therapeutic candidate should be specific to certain types of RNR. The differences in oligomerization states across the species offer an opportunity to achieve the desired specificity. We propose to design a high throughput assay to identify small molecules that stabilize the inactive states of RNRs.