FIGURE 5.

The binding mode of the C4-CoA adduct and oxalate. a, the stereo view of the active site is shown for ObcA in complex with the bisubstrate C4-CoA adduct (green) and oxalate (yellow), noting a tetrahedral carbon (black asterisk) and Co²⁺ ion (black sphere). Dashed lines are potential hydrogen bonds within an interatomic distance of 3.5 Å, and the schematic drawing for these interactions is shown in Fig. 6d. b, the model for the C4-CoA adduct, oxalate, and Co²⁺ is overlaid with an F_o − F_c electron density map at 2.3 σ. c, the binding cavity of the C4-CoA adduct and oxalate is displayed in a surface representation of ObcA, with the metal ion indicated in gray. d, the surface charge distribution of the adduct-binding region is shown in an orientation similar to Fig. 3b. Positive charge distribution and negative charge distribution are indicted in blue and red, respectively. Note that the adenosine 3′,5′-diphosphate moiety is placed in the vicinity of the positive charge.