Anionic G•U pairs in bacterial ribosomal rRNAs

(A) The fold of the three-way junction with the anionic G1099•U1086 pair with, in purple, the contacts between G1108 and the 5′-phosphate of U1095 forcing G1094 to bulge out. (B) Elements of the secondary structure of the three-way junction. The right-angle arrows indicate the coaxial stacking between the helices in the three-way junction. (C) The anionic G1099•U1086 pair with a hydrated Mg²⁺ ion (green sphere) with its hydration sphere (red spheres) and a direct contact with an anionic phosphate oxygen of U1085. The distances to the Mg²⁺ ion are between 1.9 Å and 2.1 Å, except the one to the O6(G1099). Drawings based on E. coli (PDB 8B0X, Fromm et al. 2023).