Figure 1.

Sequence and secondary structure of the trans Schistosoma hammerhead ribozyme constructs. The full construct is shown for Schist26, whereas only stem III and the corresponding P1 are shown for Schist24 through Schist20 since the rest of the construct is identical to Schist26. Construct names correspond to the number of bases in the substrate strand. The double-headed arrow indicates the tertiary loop-loop interaction between stems I and II. Canonical base pairs are shown as solid lines and the Hoogsteen base pair is shown with a ●. The conserved nucleotides that make up the catalytic core are shown in outline and numbered according to standard convention. Bold nucleotides indicate the ribozyme strand and the single headed arrow points to the scissile bond. The cleavage experiments employ a two-stranded construct consisting of the ribozyme and the full-length substrate. The ligation experiments employ a three-stranded construct consisting of the ribozyme, the 5’-cleavage product, P1, which has a 2', 3' cyclic phosphate at C¹⁷, and the 3’-cleavage product, P2, which has a 5’-OH on C¹⁸. For the UUCG control, the sequence in the stem II loop is replaced with a UUCG sequence (boxed).