Figure 9.

Binding of c-di-AMP to the RECON protein. In its complex with RECON (PDB: 5UXF), c-di-AMP adopts an E-type conformation, with both adenine bases stacked from both sides. Base Ade1 is held by a π–π stacking with Tyr24 from below and a C–H–π stacking with Leu306 from above. Base Ade2 is held by a triple hydrophobic–π interaction with Ala253 and Leu219 from above and an anion–π interaction of the carboxylate of Glu276 from below (indicated by the red arrow in panel B). In (A), dotted blue lines indicate the hydrogen bonds between N and O atoms of the Asn280 side-chain amide group and the N7 and N6 atoms of Ade2, respectively, and between Glu279 and the N6 atom of Ade2.