Fig. 7
From: Structure-based insights into self-cleavage by a four-way junctional twister-sister ribozyme
Intermolecular contacts and bound metal ions at the U6–A7 cleavage site in the structure of the env22 twister ribozyme (PDB code: 5DUN). a Schematic of the secondary fold of the env22 twister ribozyme. The sequence is color-coded according to helical segments observed in the tertiary structure. Highly conserved residues are labeled by red circles. Long-distance pseudoknot interactions observed in the tertiary structure are labeled with dashed lines named T1 (in red) and T2 (in black). b Bases U5 (modified with a 2′-OCH3 substitution) and A6 at the cleavage site of the env22 twister ribozyme are splayed apart, with U5 directed outwards and A6 directed inwards into the ribozyme fold. A6 is stacked with the A35•U30 base pair. c The non-bridging phosphate oxygens of the U5–A6 scissile phosphate form hydrogen bonds to the N1H of G48 and directly coordinated to a hydrated Mg2+ cation
