Fig. 5: Comparison of kpChbG with other CE4 enzyme family members.

a Sequence alignment based on structural alignment using PROMALS3D. The five residues forming the active site, which are critical for activity of CE4 enzymes, are indicated by asterisks (*). Four of the five residues forming the active site structurally aligned with each other are shown in red, whereas one residue, H125 on kpChbG, which does not structurally aligned, is shown in blue. The putative corresponding histidine residue with H125 of kpChbG, identified by locating the similar position in the active site of the CE4 enzyme, is linked by a dashed black line. Six loops (Loop 1~6) involved in the substrate specificity control as characterized in CE4 enzymes are indicated by colored lines under the corresponding residues. Residues used to form α7 helix in kpChbG are highlighted using orange color. b Structural superposition of kpChbG (light blue) with spPgdA (gray) and vcCDA (cyan). c Magnified region of the active site that is marked by a black-dashed box in b. Conserved residues involved in the formation of the active site are labeled. d Structural comparison of six loops in kpChbG with those of other CE4 enzymes. α7 helix, which is only present in kpChbG, is indicated by an orange-colored circle.