Cleaving DNA with DNA: Cooperative Tuning of Structure and Reactivity Driven by Copper Ions

Abstract

A copper‐dependent self‐cleaving DNA (DNAzyme or deoyxyribozyme) previously isolated by in vitro selection has been analyzed by a combination of Molecular Dynamics (MD) simulations and advanced Electron Paramagnetic Resonance (Electron Spin Resonance) EPR/ESR spectroscopy, providing insights on the structural and mechanistic features of the cleavage reaction. The modeled 46‐nucleotide deoxyribozyme in MD simulations forms duplex and triplex sub‐structures that flank a highly conserved catalytic core. The DNA self‐cleaving construct can also form a bimolecular complex that has a distinct substrate and enzyme domains. The highly dynamic structure combined with an oxidative site‐specific cleavage of the substrate are two key‐aspects to elucidate. By combining EPR/ESR spectroscopy with selectively isotopically labeled nucleotides it has been possible to overcome the major drawback related to the “metal‐soup” scenario, also known as “super‐stoichiometric” ratios of cofactors versus substrate, conventionally required for the DNA cleavage reaction within those nucleic acids‐based enzymes. The focus on the endogenous paramagnetic center (Cu2+) here described paves the way for analysis on mixtures where several different cofactors are involved. Furthermore, the insertion of cleavage reaction within more complex architectures is now a realistic perspective towards the applicability of EPR/ESR spectroscopic studies.