Fig. 1

Proteasome ubiquitin receptors. Schematic of the 26S proteasome illustrating the position of the intrinsic proteasome receptors (a) and the association of the UBA–Ubl proteins with the 19S proteasome (b). Rpn10 and Rpn13 are the predominant high affinity sites for binding ubiquitinated proteins. In yeast, Rpn1 may also facilitate binding of ubiquitinated proteins to the 19S (a). Ubl–UBA proteins, such as Rad23 and Dsk2, associate with the 26S through their Ubl domains that bind to either Rpn10 or Rpn13. The UBA domains bind the polyubiquitin chains (b)