Properties of hepatitis delta virus ribozyme, which consists of three RNA oligomer strands

Properties of a hepatitis delta virus (HDV) RNA ribozyme system, which consists of three RNA oligomer strands (substrate 8-mer; enzyme 16-mer plus 35-mer) and contains a hybrid sequence of genomic and antigenomic RNA cores, are reported. Effects of Mg2+ concentration, divalent metal ion species, pH, and temperature on the cleavage activity were examined. The substrate cleavage activity increased with increasing Mg2+ concentration (0-100 mM). Ca2+ and Mn2+ ions were the most effective divalent cations and Mg2+ was less effective. The cleavage activity increased with increasing pH (5-7.5). The optimum temperature for the cleavage activity was 25-40 degrees C. The Mg2+ concentration, pH and temperature dependencies are different from those reported for the single-strand ribozymes (about 90-mer) although the divalent metal ion preference is very similar. Conformational change induced by Mg2+ ion titration was monitored by CD. The CD data and the activity-Mg2+ concentration data were analyzed by curve-fitting analysis using equations derived for multiple metal ion binding mechanisms. The data can be explained by a model in which three Mg2+ ions bind to one ribozyme unit.