Biopolymers and cell. 1997; 13 (1): 30 - 35

Effect of pH, ionic strength, and ionic composition on efficiency of hammerhead ribozyme-mediated cleavage of the tat-RNA HIV-I in vitro

L. N. Buryanovsky

The hammerhead ribozymes like other types of ribozymes are metalloenzymes, and their activity strongly depend on divalent metal ion presence. While influence of divalent metal ions on the cleavage of substrate by the hammerhead ribozymes was well characterised, effect of monovalent kations was not analyse systematically. In the present work influence of monovalent cations (H+, K+, Li +, NH4) and buffer ions on efficiency of the tat-RNA cleavage in vitro by hammerhead ribozyme was characterized. pH-dependence was shown to be bell-shaped with an optimum at pH 7.0. Both K and Li ions at concentration O.I M increased, and at concentrations higher 0.2 M decreased efficiency of cleavage. At concentration 0.8 M reaction seemed to be completely blocked. NH4 ions had inhibitory effect at all concentrations tested. The data presented here suggest specificity of interactions of monovalent cations with ribozyme RNA, that might promote, or vice versa, prevent forming active hammerhead conformation.