Schematic diagram of different forms of the proteasome. Intracellular proteasome exists in different forms. The 26S proteasome can exist with one or two 19S caps, immunoproteasomes containing one or two 11S caps, proteasomes containing the 20S proteasome with one or two PA200 caps (in the nucleus only), and hybrid proteasomes which contain different combinations of 20S and activators.
