Structural superpositions
of the natural mouse β2c (A,C)
and β2i (B,D) subunits with their human–yeast chimeric
counterparts in the ligand-free (A,B) and ONX 0914-bound (C,D) states.
Amino acids are labeled by the one-letter code. Hydrogen bonds are
depicted by black dashed lines. Hydrophobic interactions are highlighted
by double arrows. Color coding is according to Figure 5. Note that ONX 0914 has been previously
modeled into the mouse β2 subunits as a morpholine adduct with
Thr1,13d whereas in the chimeric subunits
it was built as a seven-membered ring structure according to the revised
reaction mechanism of epoxyketones with Thr1.21 PDB IDs: 3UNE (mouse cCP), 3UNH (mouse iCP), 3UNB (mouse cCP:ONX 0914), 3UNF (mouse iCP:ONX 0914), 6HTB (hβ2c chimera), 6HV3 (hβ2i chimera), 6HTC (hβ2c chimera:ONX
0914), 6HV4 (hβ2i
chimera:ONX 0914).