Extraordinary enhancement of the cleavage activity of a DNA‐armed hammerhead ribozyme at elevated concentrations of Mg2+ ions

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Abstract
As part of an ongoing effort to characterize structure‐function relationships, activities of all‐RNA and DNA‐armed hammerhead ribozymes were examined. An analysis of the dependence on the concentration of Mg2+ ions of cleavage rates revealed that, whereas the k cat of the reaction catalyzed by the all‐RNA ribozyme reached a maximum value of about 18 min−1 at a concentration of about 200 mM Mg2+ ions, that of the DNA‐armed ribozyme increased linearly as the concentration of Mg2+ ions was increased above 300 mM, finally reaching a value of more than 100 min−1 at 700 mM Mg2+ ions. These results suggest that the potential activity of a hammerhead ribozyme might be greater than is usually recognized.