(a) Active site of the human ternary complex (PDB entry 1sir
; Fu et al., 2004), showing key interactions between FAD (black), the substrate mimic NBC (white) and key protein residues (gray). (b) Overlay of the active site in (a) with that of apo GCDH from B. pseudomallei (green; PDB entry 3eom
), highlighting the nearly 180° rotation of Tyr373 in the bacterial structure relative to Tyr369 in human GCDH. (c) Overlay of the active site in (a) with that of the bacterial structure bound to two molecules of FOL680 (orange; PDB entry 3gqt
). Backbone devations occur downstream of the catalytic glutamate, while Tyr373 is rotated back to the position seen in the human complex. (d) Overlay of the apo and FOL680-bound bacterial GCDH active sites.