Comparison of the structure of WT and G230A hSTING CTDs complexed to c-di-GMP.

<p>(A) A summary of known structures of apo-hSTING CTD and hSTING CTD-c-di-GMP complex. The amino acids substitutions in the structures are labeled in bold. (B) Overlay of G230A-STING:c-di-GMP dimer and the WT-STING:c-di-GMP dimer. The structures are from 4F5E and 4F5D of the PDB. The WT dimer is rendered with magenta ribbon and the c-di-GMP is shown as orange solid surface. The G230A mutant dimer is shown as blue ribbon (cyan: subunit A and blue: subunit B). Compare to all other structures (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0077846#pone-0077846-g001" target="_blank">Figure 1</a>), the subunit A of the ligand bound G230A structure shows the dramatic positional change indicated by an arrow. (C) Closer view of c-di-GMP and the lid region. The loop to ribbon transition in the lid region of the mutant structure is depicted and, within the dimer, Subunit A is located relatively closer to subunit B than in the WT CTD. (D) The conformational change of the lid region of G230A CTD that leads to a more ordered ligand binding. The ligand is shown in orange or yellow sticks and Mg²⁺ is shown as green ball. Residue 230 is colored green. (E) Superposition of Apo WT hSTING (golden brown) and R232H hSTING complexed with c-di-GMPs (cyan).