FIGURE 5.

Schematic representation of the cross-linking experiments performed using various mutated and modified ribozymes. (A) Cross-link experiments were performed using the SdA-1s⁴U-2 substrate and either the U23A, disrupted P1.1 (i.e., possesses four U instead of two GC bp), G28A, G28C, or the C76A mutant ribozymes. The cross-linked species (X1 to X4) are identified adjacent to the mutations that are boxed. The most abundant species are underlined. (B) Identification of the seven positions where s⁴U residues were introduced in the RNA–DNA mixed ribozymes. The positions are identified by the circles. The deoxyribonucleotide regions are boxed. The cross-link between the positions U23 of the ribozyme and C + 5 (circled) of the substrate is identified by the dotted line.