Figure 3: Schematic representation of the covalent trimer concept.

(a) Schematic representation of the assembly of the hDUT^F158W dUTPase. Green spheres represent the sensor-bearing hDUT^F158W subunits. The structures reaching out from the subunits represent the swapping C-terminal arm of dUTPase. Yellow stars mark the tryptophan serving as intrinsic fluorescence signal of the enzyme conformations. The pink sphere indicates a Mg²⁺ ion. (b) Schematic representation of the covalent pseudotrimers. The projection of the swapping arms with color transition represents the flexible linkers connecting the C-terminus of one dUTPase protomer to the N-terminus of another one. Different colors of the protomers represent the possible heterogeneity within the trimer, i.e. every protomer can be changed independently from each other. (c) SDS-PAGE analysis of the purified WWW enzyme. The main band is located at the expected position which corresponds to the calculated molecular weight of 58064 Da.