Figure 1: Representation of the 26S proteasome. (a) The 26S proteasome consists of a 20S core capped by one or two 19S activators. The catalytic subunits β1, β2 and β5 are represented in blue in the β-ring. (b) A schematic model of the 20S core, indicating the presence of cleavage sites inside the barrel-shaped structure.