English: Schematic and tertiary structure of the twister-sister ribozyme. a Schematic of the secondary fold of the dC62-containing four-way junctional twister-sister ribozyme. The sequence is color-coded according to helical segments observed in the tertiary structure. All highly conserved residues are labeled by red circles. Long-distance interactions observed in the tertiary structure are labeled with dashed lines named T1 (in red) and T2 (in black). The cleavage site step was shown by a red arrow. b Schematic of the tertiary fold based on the crystal structure of the dC62-containing four-way junctional twister-sister ribozyme. c A ribbon view of the 2 Å structure of the four-way junctional twister-sister ribozyme color-coded as shown in a and b. The divalent metal ions identified in the tertiary structure are shown as green balls. d Highly conserved residues (shown in red) are brought into close proximity by the interaction between partially zippered-up L1 and SL4 loops in the tertiary fold of the twister-sister ribozyme