Figure 6.

Cleavage activity assays of various mutants of the J4/2 junction. The inset shows a typical autoradiogram of a PAGE gel for a 30 min reaction for each ribozyme tested. The secondary structure of the wild-type ribozyme is illustrated entirely on the left, while only the P2 stem, J4/2 junction and the most relevant nucleotides are illustrated for the mutants. The mutations and insertion are denoted by squared and circled nucleotides, respectively, while deletions are indicated by a triangle (▵). The lane numbers at the top of the autoradiogram correspond to the number of each ribozyme: 1, wild-type; 2, RzA₇₈U,A₇₉U; 3, Rz–U⁺_79–80; 4, Rz–C₁₉A,G₈₁U,G₈₀A; 5, Rz–U⁺_76–77; 6, Rz–▵77; 7 is the original bimolecular construct (RzA–RzB); and, 8, the bimolecular construct including an abasic residue (Ab) in position 77 (RzB–Ab77). The positions of the substrate and product are indicated adjacent to the gel. The rate constants (k_obs) for each ribozyme are indicated below the gel.