... two residues and the edge of the substrate ring could prevent bind-ing of 3,6-DMC and 3,5-DMC, as shown in Fig. 2-D,E,F. Thus, the binding of 3,5-DMC and 3,6-DMCto the active site of C2,3O could ... surrounding the binding pocket. The two complexes were very sim-ilar. In both structures, the largest contacts were foundbetween the plane of the substrate ring and the plane of the imidazole ring ... onlywhen the side chain makes the closest con-tact between the residue and the substrate.Lines with round ends indicate stackingbetween the ring of the substrate and His240 in DHBD (A), His248 in...