Fig 1. Comparison of putative spatial structure of CsHK with hHK-IV or rHK-In.

(A) Ribbon drawing of superposed structure models of CsHK (green and light green) and closed-form hHK-IV (red and light red, PDB: 1V4S_A), which structures are complexed with glucose (blue ball) and MRK (N-thiazol-2-yl-2-amino-4-fluoro-5-(1-methylimidazol-2-yl) thiobenzamide, an allosteric activator, yellow ball). The α 13 helix (magenta and light green) is included in the small domain of the closed-form. (B) Ribbon drawing of superposed structure models of CsHK (green and light green) and rHK-In (yellow and light yellow, PDB: 1BG3_B), which structures are complexed with glucose (blue ball) and G6P (red ball). The α 13 helix (magenta and light green) is included in the small domain of the closed form. The structures of the α 13 helix and connecting region I (brown and light green) are different. (C) Stereo view of the allosteric sites in closed-form hHK-IV (left) and CsHK (right). In the left panel, the allosteric sites are located below connecting region I (brown, ribbon model). MRK (yellow stick) forms hydrogen bonds with ARG63 and TYR215 (red stick) and hydrophobically interacts with MET210, TYR214 (red stick) of α 5 helix (red ribbon) and V452, V455 (magenta stick) of α 13 helix (magenta ribbon). The supposed corresponding structure of CsHK is shown in the right panel. (D) Stereo view of G6P binding sites in rHK-In (left) and CsHK (right). Interactions of G6P (red stick) with the large (yellow) and small (light yellow) domain of the rHK-In binding cleft are shown in the left panel. SER/THR residues are colored light blue (stick), and ASP residues are orange (stick). Glucose (blue stick) is bound at an adjacent position in the cleft. The ARG174 side chain unique to rHK-In is shown in magenta (stick). The supposed corresponding structure of CsHK is shown in the right panel.