Figure 5: Inositol phosphate-binding site for EhIP6KA.
(a) Binding of Ins(1,4,5)P3 (stick and ball model; green for carbon, red for oxygen and orange for phosphorus atoms. The phosphate groups are numbered). The refined 2Fo−Fc electron density map is contoured at 1.3σ. (b) Overlay of InsP6 (grey stick model with orange and red phosphate groups) and Ins(1,4,5)P3 (green stick). (c) Overlay of InsP6 and Ins(1,3,4,5,6)P5 (cyan stick). (d) Binding of InsP6 (stick and ball model; green for carbon, red for oxygen and orange for phosphorus atoms). The phosphate groups are numbered. Amino acids are shown as stick models. The refined 2Fo−Fc electron density map is contoured at 1.3σ. (e), Electrostatic surface plot with blue and red coloration to respectively indicate positive and negative electrostatic potentials at physiological pH. In the magnified surface representation, the positions of the 310 helix and IP helices are highlighted. Bound InsP6 is depicted as a stick model. Also shown are surface representation of Ins(1,4,5)P3 in the active site of HsIP3K (data from ref. 32) and the active site of ScIPMK (data from ref. 26; crystals did not contain substrate).
