Figure 7.

Three-dimensional superposition of the active sites of the CtFDO complexes. FAD and formic acid (FMT) molecules and selected residues at distances of up to 3.8 Å from the ligands are shown with C atoms coloured magenta, pale green and light grey, respectively. The insets show the binding of the moieties of the ligands with regard to individual subsites. (a) Alignment of CtFDO:MAMB (PDB entry 6ze3), CtFDO:PESB (PDB entry 6ze4) and CtFDO:IPEA (PDB entry 6ze5). The ligands MAMB, PESB and IPEA are shown with C atoms coloured hot pink, green and yellow, respectively. (b) Superposition of CtFDO:4NC (PDB entry 6ze6), CtFDO:4NP (PDB entry 6ze7) and CtFDO:ABTS (PDB entry 7aa2). The ligands 4NC, 4NP and ABTS are shown with C atoms coloured cyan, orange and black, respectively. (c) Schematic pattern of ligand composition. Of all of the compounds used for CtFDO–ligand complex preparation, only those containing an aromatic group (except for formic acid) were found binding in the internal pocket. Hexagons, red lines and black circles with a minus sign on a yellow background represent the binding of aromatic rings, aliphatic moieties and negatively charged moieties in the active-site pocket, respectively. The pattern indicates a polyaromatic composition of the putative substrate. Molecular graphics were created with PyMOL (Schrödinger).