FIGURE 1.

The overall reaction of oxalogenesis in B. glumae and the structure of ObcA. a, in ObcA-dependent catalysis, acetyl-CoA (black) and oxaloacetate (red) are proposed to be converted into a C6-CoA adduct (12). The oxalo group of the adduct is colored in blue. Subsequently, ObcB produces CoA, acetoacetate, and oxalic acid. In citrate synthesis, citrate is produced via the citroyl-CoA intermediate (13). b, the overall structure of ObcA in a ligand-free form is displayed, indicating an N-domain (blue) and a C-terminal (β/α)₈-barrel fold (magenta). Additional structural elements from the C-domain (green), β1 (yellow), and a metal ion (green sphere) are also indicated. c, the topology of ObcA is shown with color coding identical to that described in b. The C terminus of β_N1 to the N terminus of α_N3 is highly disordered and not modeled. Those termini are marked with black dots. Secondary structure elements are shown in Fig. 2.