Altered Mg2+ dependence of glmS ribozyme constructs with 3′ -end truncations. (A) Secondary structure model of B. subtilis 246 glmS RNA. Circled nucleotides correspond to the 3′ termini of individual truncated RNAs, whose names (P2 term, P4 term, P3a term) refer to the 3′-most stem element completely contained within the respective construct. Two additional engineered glmS ribozyme variants (each terminating at C183) individually disrupt and restore base-pairing in the P3a pseudoknot (boxed). Bracketed symbols are used on the plot in B to represent the Mg2+ dependence of the corresponding variants. Arrowhead indicates the cleavage site. The G residues marked by asterisks were introduced to facilitate transcription in vitro. (B) Effect of Mg2+ concentration on the cleavage rates of the glmS ribozyme variants described in A.
