(a) A single protomer of apo BpGCDH (green; PDB entry 3eom
) overlaid with the human ternary complex (gray; PDB entry 1sir
; Fu et al., 2004) containing FAD (black) and the substrate mimic NBC (white). Regions of structural difference between the two protomers (bacterial, magenta; human, yellow and cyan) are largely contained within terminal loop regions. (b) The interface between two protomers of bacterial (green/orange) and human (dark gray/white) GCDH. The human ternary complex reveals an α-helical contact region between protomers (yellow) which is a less ordered loop in BpGCDH (magenta). Density modeled on the opposite protomer in the human complex (cyan) is too disordered to model in the bacterial apo crystal data set.