The Role of Metals in the Reaction Catalyzed by Metal-Ion-Independent Bacillary RNase

Figure 4

Binding site of Mn²⁺ and Mg²⁺ ions in RNA. Noncanonical (G•A) (а) and canonical Watson-Crick (G:C) (c) binding of RNA nucleotides. Thermodynamic stability of G•A and G:C (b) pairs is due to four and three hydrogen bonds, respectively. Hydrated ions of Mn²⁺ or Mg²⁺ (water molecules that are involved in coordination of RNA by metal ions are not depicted in the figure) coordinated the N7 level of guanine for the G:C pair and oxygen phosphoric acid residue of the adjacent phosphodiester bond; Mn²⁺ has a greater affinity to nucleophilic nitrogenous bases, and Mg²⁺ tends to form a rigid bond of P–O.