3.5.2.15	crystallized with its natural substrate cyanuric acid by hanging drop, vapor-diffusion experiment in which equal volume of protein (12 mg/ml concentration) and reservoir solution are mixed and allowed to equilibrate against the reservoir at 20 °C. Crystal structure at 2.19 A resolution shows a large displacement of the catalytic lysine (Lys163) in domain 2 away from the active site core, whereas the two other active site lysines from the two other domains are not able to move	
3.5.2.15	Toblerone fold. Product of concatenation of three proteins of YjdF fold. PDB IDs 4BVT, 4BVS, 4BVR, 4BVQ, native enzyme and in complex with melamine, barbituric acid, and cyanuric acid and Xe-derivative, to 1.9, 2.6, 3.1, 2.6 and 2.55 A resolution, respectively. The AtzD monomer, active site and substrate all possess threefold rotational symmetry, to the extent that the active site possesses three potential Ser–Lys catalytic dyads. A single catalytic dyad, Ser85–Lys42, is hypothesized, based on biochemical evidence and crystallographic data