Figure 2.

Schematic illustration of the proteasomal substrate binding channel with non-primed (S) and primed (S’) specificity pockets interacting with the amino acid side chains (P-sites) of a peptide. The proteolytically active β-subunit features the active site Thr1 and all other catalytic residues, while the neighboring β-subunits contribute specificity pockets only to the substrate binding channel and do not necessarily feature their own active site.