Figure 4.

Structural analysis of the crystal complex of TuUGT202A2 in the presence of UDP and (S)-naringenin.A, chemical structure and labeling of hydroxyl groups of (S)-naringenin (NAR). B, chain A atomistic representation of the interactions between enzyme (carbon atoms in tan color) and the two ligands: UDP (carbon atoms in white) and NAR (carbon atoms in green). The observed hydrogen bonds between ligands and enzyme are shown in green color. Asp140 is displayed due to its importance in catalysis as part of the conserved His-Asp catalytic dyad, although it was not located within the cut-off distance. C, chain B atomistic representation of TuUGT202A2 catalytic site in the presence of UDP and NAR (coloring follows the same scheme as (A)). D, superimposition of chain A and B from PDB: 8GKN. Only (S)-naringenin and residues 106–115 have been colored to highlight the conformational difference between chain A, in salmon, and chain B, in light blue, and the different orientation of the ligand in each chain. The distances between the backbone of Thr110 from both chains were measured using UCSF Chimera. The predicted hydrogen bond between Thr110.A and (S)-naringenin is shown in a solid yellow line. UGT, UDP glycosyltransferase.