The naturally trans-acting ribozyme RNase P RNA has leadzyme properties

Divalent metal ions promote hydrolysis of RNA back-bones generating 50OH and 20;30P as cleavage pro-ducts. In these reactions, the neighboring 20OH act as the nucleophile. RNA catalyzed reactions also require divalent metal ions and a number of different metal ions function in RNA mediated cleavage of RNA. In one case, the LZV leadzyme, it was shown that this catalytic RNA requires lead for catalysis. So far, none of the naturally isolated ribozymes have been demon-strated to use lead to activate the nucleophile. Here we provide evidence that RNase P RNA, a naturally trans-acting ribozyme, has leadzyme properties. But, in contrast to LZV RNA, RNase P RNA mediated cleavage promoted by Pb21 results in 50 phosphate and 30OH as cleavage products. Based on our findings, we infer that Pb21 activates H2O to act as the nucleophile and we identified residues both in the substrate and RNase P RNA that most likely influenced the position-ing of Pb21 at the cleavage site. Our data suggest that Pb21 can promote cleavage of RNA by activating either an inner sphere H2O or a neighboring 2 0OH to act as nucleophile