Figure 5. Rare nucleotide variations observed in the cores of some hammerhead ribozymes.

(A) Consensus secondary structure of the hammerhead core with highly conserved residues in yellow and variable residues in gray. Blue letters designate active natural variants tested previously. Red and green letters designate natural variations tested in this study that are expected to have deleterious effects or neutral/compensatory effects, respectively, on ribozyme function. (B) Atomic-resolution structure of portions of the Schistosoma mansoni hammerhead core. Colors are as defined in (A), with the addition of yellow designating strictly conserved nucleotides (built from PDB accession 2GOZ with pymol [66]). Stem I is in cyan, stem II in red, and arrows indicate position of insertions. Dashed lines in red and green represent hydrogen bonds that are expected to be disrupted or maintained, respectively. Other notations are as described for Figure 2. For complete secondary structure and additional information on these variants see Figure S6 and Figure S7 for variants that were inactive.