Figure 1
From: Role and Function of the 26S Proteasome in Proliferation and Apoptosis
Subunit composition of and protein degradation by the 26S proteasome (schematic). The 20S catalytic core complex consists of four axially stacked seven-membered rings: two inner rings formed by β subunits (dark blue) carrying proteolytic sites faced to the central cavity of the 20S complex, and two outer rings formed by nonproteolytic α subunits (light brown). The 19S regulatory complex consists of the base subcomplex and the lid subcomplex. The base subcomplex contains six AAA-ATPase subunits (light blue) and two accessory subunits. The lid subcomplex contains eight subunits (yellow). 1, A substrate protein is targeted for proteasomal degradation by the covalent attachment of ubiquitin monomers (red balls). This has been governed previously by ubiquitin-activating enzymes (E1), ubiquitin-conjugating enzymes (E2), and ubiquitin-protein ligases (E3). 2, The substrate protein enters the 19S regulatory complex, is recognized, deubiquitinated, unfolded, and translocated into the central cavity of the 20S catalytic core complex, where it is degraded by different hydrolytic activities. 3, Short peptides as a product of degradation are released at the opposite end of the 26S proteasome.
