Figure 5

Conformational changes of TcAkt-PH loop regions induced by binding of different InsP ligands. (a) Table of loop-to-helix transitions of TcAkt-PH interacting with Ins(1,3,4,5)P₄, Ins(1,3,4)P₃, Ins(1,4,5)P₃ or Ins(1,3,5)P₃. As determined by NMR experiments, strongest binder Ins(1,3,4,5)P₄, stabilizes loop-to-π-helix transitions in stretches 15–17 and 46–48 and simultaneously destabilizes region 41–43. Ins(1,3,5)P₃ reduces the π-helix tendency of stretch 15–17 but induces π-helix formation in regions 41–43 and 52–54. Ligands Ins(1,3,4)P₃ and Ins(1,4,5)P₃ induce less conformational changes compared to Ins(1,3,4,5)P₄ and Ins(1,3,5)P₃, showing a significant impact mainly in region 15–17 of TcAkt-PH. Ins(1,4,5)P₃ stabilizes a π-helix in 13–15, similar to Ins(1,3,4,5)P₄, whereas Ins(1,3,4)P₃ represents the only ligand that induces a 3₁₀-helix formation in stretch 15–17. (b-d) MD determined protein–ligand structures of TcAkt-PH interacting with (b) Ins(1,3,4)P₃, (c) Ins(1,4,5)P₃ and (d) Ins(1,3,5)P₃: Interacting residues are shown in sticks, contacts in dashed yellow lines, phosphate groups in red (ball representation). The presented frames were carefully chosen from the last 1 µs MD simulation to showcase the interacting residues adequately.