ROLES OF 2'-HYDROXYLS OF LEADZYME ON AN RNA CLEAVAGE

The roles of two different 2'-hydroxyls near to a catalytic site of a leadzyme (Pb2+ ribozyme), CUGGGAGUCC, have been investigated kinetical ly. These roles of two different 2'-hydroxyls were clearly distinguish ed upon a cleavage reaction of an RNA substrate. One 2'-hydroxyl of G of the leadzyme in an asymmetry internal loop contributed to only the binding constant for the leadzyme with the substrates. The other 2'-hy droxyl of A in the asymmetry loop contributed to only the cleavage rat e constant. On the basis of the results, we propose the possibility of the formation of a hydrogen bond between the 2'-hydroxyl of G of the leadzyme and the substrate and the binding between Pb2+ ion and the 2' -hydroxyl of A.