FIGURE 1.
Schematic diagrams of the hairpin ribozyme chemical reaction and variants at position 38. (A) The chemical reaction of the hairpin ribozyme where X: and XH are proton shuttling groups. The reaction proceeds via a trigonal-bipyramidal transition state. (B) The base structures, cleavage activity relative to WT, and solution pKa values of base imino groups (arrows). Enzymatic rate values were recorded at 25°C at pH 7.5 in the context of a 4WJ construct (Kuzmin et al. 2005). Solution pKa values were derived by the 5′-monophosphorylated nucleoside (Ward et al. 1969; Saenger 1984).