Influence of monovalent metal ions on metal binding and catalytic activity of the 10–23 DNAzyme

Deoxyribozymes (DNAzymes) are single-stranded DNA molecules that catalyze a broad range of chemical reactions. The 10–23 DNAzyme catalyzes the cleavage of RNA strands and can be designed to cleave essentially any target RNA, which makes it particularly interesting for therapeutic and biosensing applications. The activity of this DNAzyme in vitro is considerably higher than in cells, which was suggested to be a result of the low intracellular concentration of bioavailable divalent cations. While the interaction of the 10–23 DNAzyme with divalent metal ions was studied extensively, the influence of monovalent metal ions on its activity remains poorly understood. Here, we characterize the influence of monovalent and divalent cations on the 10–23 DNAzyme utilizing functional and biophysical techniques. Our results show that Na⁺ and K⁺ affect the binding of divalent metal ions to the DNAzyme:RNA complex and considerably modulate the reaction rates of RNA cleavage. We observe an opposite effect of high levels of Na⁺ and K⁺ concentrations on Mg²⁺- and Mn²⁺-induced reactions, revealing a different interplay of these metals in catalysis. Based on these findings, we propose a model for the interaction of metal ions with the DNAzyme:RNA complex.