Figure 7.

PyPrx6 active site depicting the sulfinic acid and the binding orientations of glycerol. (A) Fc-Fo omit map (1.62 σ) of the active site from the 4 chains within the asymmetric unit of PyPrx6 (PDB: 3TB2) showing the density assigned to both the sulfinic acid of C_P and the glycerol bound in the active site. Glycerol and sulfinic acid are labelled as GOL and CSD, respectively. Note that the carbons are yellow, sulfur is green, oxygen is red, and nitrogen is blue. (B) A comparison of the binding orientations of each of the glycerol molecules of PyPrx6 relative to H₂O₂ derived from an alignment with the ApTrx-H₂O₂ structure (PDB: 3A2V) with our PyPrx6 structure. The H₂O₂ is shown as the red oxygen atoms with positions O_A and O_B labelled, while the 4 glycerol molecules in the PyPrx6 structure are shown with different coloured backbones and red oxygen atoms. Note that in each case, the terminal oxygen of the glycerol molecule aligns with position O_B. (C) For comparison, from a similar structural alignment the known binding orientations for glycerol (from PDB: 3A2W (ApTrx, chains A and C with the glycerol molecules depicted in pink and green, respectively) are compared to the same binding of H₂O₂ (PDB: 3A2V). Note that for ApTrx chain A, the glycerol terminal oxygen aligns with position O_A, while the glycerol molecule from ApTrx chain C has oxygen atoms aligning with positions O_A and O_B as was previously reported [37] All structural alignments derived from the alignment of the following conserved residues PxxxxTxxC_P, as was done previously [37].